There’s one thing that the Apple Mail client gets right which I’ve never seen anything else try to do - the way it formats messages. Most mail clients seem to offer plain text and HTML as user selectable options and do exactly what they’re told regardless of the content of the message. If HTML is enabled they always send a mail with both text/plain and text/html renditions of the message. Normally the plain text version is a fixed, 80 column version. This is wasteful of bandwidth, especially since very few users actually use any formatting at all, and means that mail programs that don’t do HTML have to treat the mails as though the fixed layout the sending system chooses is important even when it results in poor layout (for example, on mobile devices with small screens). What Apple Mail does here is to only enable the more complex formatting options if they add information that can’t be represented in the less complex formats. By default mails are sent in text/plain with the format=flowed option to let the reader know it can safely reflow the text and no HTML alternative is generated. If something that can’t be represented using format=flowed is included in the message then a HTML alternative is generated - transparently and without user intervention. This is good partly because it’s nice to see format=flowed used, it’s a nice technical solution to the problem, but mostly because it’s great user interface design. Most Apple Mail users will never notice if it is or isn’t generating HTML e-mail, they’ll just see that it’s doing what they expect and won’t have to deal with an option that they probably don’t understand or have much of a view on. Other users won’t be troubled with HTML generated by Apple Mail users unless there is some content in the formatting. It’d be good to see more MUAs implementing similar behavior, at least optionally.

I just read an interesting post about latency and how it affects web sites [1]. The post has some good ideas but unfortunately mixed information on some esoteric technologies such as infiniband that are not generally applicable with material that is of wide use (such as ping times). The post starts by describing the latency requirements of Amazon and stock broking companies. It’s obvious that stock brokers have a great desire to reduce latency, it’s also not surprising that Google and Amazon analyse the statistics of their operations and make changes to increase their results by a few percent. But it seems to be a widely held belief that personal web sites are exempt from such requirements. The purpose of creating content on a web site is to have people read it, if you can get an increase in traffic of a few percent by having a faster site and if those readers refer others then it seems likely to have the potential to significantly improve the result. Note that an increase in readership through a better experience is likely to be exponential, and an exponential increase of a few percent a year will eventually add up (an increase of 4% a year will double the traffic in 18 years). I have been considering hosting my blog somewhere else for a while. My blog is currently doing about 3G of traffic a month which averages out to just over 1KB/s, peaks will of course be a lot greater than that and the 512Kb/s of the Internet connection would probably be a limit even if it wasn’t for the other sites onn the same link. The link in question is being used for serving about 8G of web data per month and there is some mail server use which also takes bandwidth. So performance is often unpleasantly slow. For a small site such as mine the most relevant issues seem to be based around available bandwidth, swap space use (or the lack therof), disk IO (for when things don’t fit in cache) and available CPU power exceeding the requirements. For hosting in Australia (as I do right now) bandwidth is a problem. Internet connectivity is not cheap in any way and bandwidth is always limited. Also the latency of connections from Australia to other parts of the world often is not as good as desired (especially if using cheap hosting as I currently do). According to Webalizer only 3.14% of the people who access my blog are from Australia, they will get better access to my site if hosted in Australia, and maybe the 0.15% of people who access my blog from New Zealand will also benefit from the locality of sites hosted in Australia. But the 37% of readers who are described as “US Commercial” (presumably .com) and the 6% described as “United States” (presumably .us) will benefit from US hosting, as will most of the 30% who are described as “Network” (.net I guess). For getting good network bandwidth it seems that the best option is to choose what seems to be the best ISP in the US that I can afford, where determining what is “best” is largely based on rumour. One of the comments on my post about virtual servers and swap space [2] suggested just not using swap and referenced the Amazon EC2 (Elastic Computing) cloud service and the Gandi.net hosting (which is in limited beta and not generally available). The Amazon EC2 clound service [3] has a minimum offering of 1.7G of RAM, 1EC2 Compute Unit (equivalent to a 1.0-1.2GHz 2007 Opteron or 2007 Xeon processor), 160G of “instance storage” (local disk for an instance) running 32bit software. Currently my server is using 12% of a Celeron 2.4GHz CPU on average (which includes a mail server with lots of anti-spam measures, Venus, and other things). Running just the web sites on 1EC2 Compute Unit should use significantly less than 25% of a 1.0GHz Opteron. I’m currently using 400M of RAM for my DomU (although the MySQL server is in a different DomU). 1.7G of RAM for my web sites is heaps even when including a MySQL server. Currently a MySQL dump of my blog is just under 10M of data, with 1.7G of RAM the database should stay entirely in RAM which will avoid the disk IO issues. I could probably use about 1/3 of that much RAM and still not swap. The cost of EC2 is $US0.10 per hour of uptime (for a small server), so that’s $US74.40 per month. The cost for data transfer is 17 cents a GIG for sending and 10 cents a gig for receiving (bulk discounts are available for multiple terabytes per month). I am not going to pay $74 per month to host my blog. But sharing that cost with other people might be a viable option. An EC2 instance provides up to 5 “Elastic IP addresses” (public addresses that can be mapped to instances) which are free when they are being used (there is a cost of one cent per hour for unused addresses - not a problem for me as I want 24*7 uptime). So it should be relatively easy to divide the costs of an EC2 instance among five people by accounting for data transfer per IP address. Hosting five web sites that use the same software (MySQL and Apache for example) should reduce memory use and allow more effective caching. A small server on EC2 costs about five times more than one of the cheap DomU systems that I have previously investigated [4] but provides ten times the RAM. While the RAM is impressive, I have to wonder about CPU scheduling and disk IO performance. I guess I can avoid disk IO on the critical paths by relying on caching and not doing synchronous writes to log files. That just leaves CPU scheduling as a potential area where it could fall down. Here is an interesting post describing how to use EC2 [5]. Another thing to consider is changing blog software. I currently use Wordpress which is more CPU intensive than some other options (due to being written in PHP), is slightly memory hungry (PHP and MySQL), and doesn’t have the best security history. It seems that an ideal blog design would use a language such as Java or PHP for comments and use static pages for the main article (with the comments in a frame or loaded by JavaScript). Then the main article would load quickly and comments (which probably aren’t read by most users) would get loaded later.

• [1] http://highscalability.com/latency-everywhere-and-it-costs-you-sales-how-crush-it


• [2] http://etbe.coker.com.au/2008/08/27/killing-servers-virtualisation-and-swap/


• [3] http://www.amazon.com/b/?node=201590011


• [4] http://etbe.coker.com.au/2008/05/28/xen-hosting/


• [5] http://www.protocolostomy.com/2008/08/27/more-adventures-in-amazon-ec2-and-ebs/

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The McCain campaign made a great tactical move by choosing Sarah Palin. She appeals to all the constituencies where McCain was weak: women, Christians, Libertarians, small state residents, energy policy wonks, corruption fighters, capitalists, gun enthusiasts, and Tina Fey fetishists. Downsides? She is inexperienced in national affairs but I really don't think the average voter will care. After all many of them were willing to overlook a similar level of inexperience in Obama. And there is one minor possible ethics situation which again will only excite the true believers. When it turns out to be overblown it may actually rebound in Palins favor as an example of MSM manipulation. She can also take the change meme away from the Democrats though that was already on the rocks what with the FISA vote and the choice of Neil Kinnock as his VP nominee. No, the lacklustre convention in Denver clearly showed that far from being the post-ideological, audaciously hopeful candidate of the future, Barack Obama is merely John Kerry with rhythm. So what do the Dems have have left? The traditional Democratic themes of "We're not Bush" (that worked sooo well the last two times didn't it?) and "The Earth is about to explode in a fiery cataclysm." As the situation in Iraq improves, the economy climbs upwards from recession and petrol prices continue to come down its going to be harder to sustain the necessary level of gloom and doom. While Republicans shouldn't exhale just yet (and the title of this post is just a teensy bit hyperbolic,) things are looking pretty good for us at the moment.

As per the original press release:

In Quebec, access to public markets is the rule while contracts attribution without invitation to tender is the exception. A public market should be transparent, fair and most importantly, open to all. The solutions as well as the propositions must be evaluated objectively on known and accepted criteria. Furthermore, the regulation implies that public markets have to enhance the local economic development as well as the Quebec technologies. From February to June 2008, FACIL has noticed sales of proprietary software for more than 25 million dollars. These purchases were made for products offered by large multinational enterprises, with no regard to suppliers in Quebec.

Much to my surprise, news about this lawsuit have spread as far as Vietnam! Something tells me that this court case might have lasting repercussions...

In the mid 90’s I was part-owner of a small ISP. We had given out Trumpet Winsock [1] to a large number of customers and couldn’t convert them to anything else. Unfortunately a new release of the Linux kernel (from memory I think it was 2.0) happened to not work with Trumpet Winsock. Not wanting to stick to the old kernel I decided to install a Linux machine running a 1.2.x kernel for the sole purpose of proxying connections for the Winsock users. I had a 386 machine with 8M of RAM that was suitable for the purpose. At that time hard disks were moderately expensive, and the servers were stored in a hot place which tended to make drives die more rapidly than they might otherwise. So I didn’t want to use a hard disk for that purpose. I configured the machine to boot from a floppy disk (CD-ROM drives also weren’t cheap then) and use an NFS root filesystem. The problem was that it needed slightly more than 8M of RAM and swapping to NFS was not supported. My solution was to mount the floppy disk read-write and use a swap file on the floppy. The performance difference between floppy disks and hard disks was probably about a factor of 10 or 20 - but they were both glacially slow when compared to main memory. After running for about half an hour the machine achieved a state where about 400K of unused data was paged out and the floppy drive would then hardly ever be used. I had initially expected that the floppy disk would get a lot of use and wear out, I had prepared a few spare disks so that they could be swapped in case of read errors. But in about a year of service I don’t recall having a bad sector on a floppy (I replaced the floppy whenever I upgraded the kernel or rebooted for any other reason as a routine precaution). Does anyone have an anecdote to beat that?

• [1] http://en.wikipedia.org/wiki/Trumpet_Winsock

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I first read about Y Combinator while browsing Paul Graham s website. I am a huge fan of his and have tried many times to bring him to Brazil for FISL (unsuccessfully so far). By that time I was updating a lecture of mine where I quote something from his Hackers and Painters essay and sudenly I noted an YC link on the left, and decided to click to learn what was that. Y Combinator is a venture capital firm to help start-ups. It was built on the concept that not much money is needed for first-stage start-ups ( from idea to company , as they call it). Quite a concept! I lost track of it until yesterday, when I read this blog post summarizing one of its events for start-ups. I found it amazing how far it came in such little time. They ve already funded about 100 start-ups, some of them really interesting. Of those presented in that post, Posterous is one I found most interesting. They create instant blogs just by sending emails to some address. There s no sign-up procedure Just send the email with any attachments and voil . There you have: a new blog. Many others are really interesting (PollEveryWhere, IDidWork, Frogmetrics, just to name a few), so I really suggest reading that post. I think Y Combinator is another great idea from Paul Graham, and I will be following it more closely, as a way to keep myself updated Who knows maybe I can get them to come to FISL to present that! ;-)

The Debian Live team is pleased to announce the first beta of Debian Lenny's Live images. Although we missed releasing images for Etch along with the installer images, we are now prepared to release live images within the regular Lenny release process. This is the first official release of Debian Live and the whole team has been working hard during the past 2.5 years to make Debian's own live systems become a reality. Nevertheless, we do need your help to find more bugs and improve the live systems, so please try them out. The images are available at:

	http://cdimage.debian.org/cdimage/lenny_live_beta1/

Please also have a look at the known issues listed below. Main features 100% Debian The build process of Debian Live basically consists of creating a Debian chroot, installing one or more kernels along with live-initramfs (a set of hooks into initramfs-tools for handling booting from read-only media) and generating a bootable image from that. This process is handled by live-helper, a collection of shell scripts that allow us to automate and customize this process. Considerable care is taken to ensure that the resulting live system is not tainted by the host system and that installed packages are not modified morethan absolutely necessary. This ensures that Debian Live really is Debian, and not "just another" a Debian-based live system. Flavours Although live-helper is a toolkit to produce your very own live systems with only a few steps, we also provide prebuilt images that are meant to be used as reference systems for end-users. Currently, this consists of the three major desktop environments (GNOME, KDE and Xfce), as well as a small 'standard' image without a graphical environment. For the desktop environments, package selection is performed by 'tasksel' with the respective desktop task, whilst the 'standard' image contains only packages of "Priority: standard" or greater, notwithstanding a handful of live-specific packages (console-common, eject, file, kbd, live-initramfs, locales, sudo and vim-tiny). Image types Debian Live offers prebuilt images for CD/DVD discs, USB sticks (or any HD-media-like device), tarballs (for PXE netboot) as well as a bare squashfs image to boot from the web directly. Live Magic Live Magic is an GUI frontend around the live-helper scripts, offering a subset of the features of live-helper in an easy-to-use graphical user interface. live-magic 1.0 was recently uploaded to sid and is the recommended version. It currently supports 7 languages. Live Installer Live Installer is a special udeb for the Debian Installer that (optionally) replaces a part of d-i in order to install the system from the live image instead of to bootstrapping it from .deb packages. This way, a live system can be easily installed to the harddisk, ensuring that the look and feel of the installation (including preseeding) works the same as the regular installer process. Unfortunately, live-installer does still have a few minor bugs left and is thus not included in our builds yet; we hope to be able to include it in the next beta. Known issues in this release

• The prebuilt images for gnome-desktop and kde-desktop are a bit too big to fit on a CD. Although the automatic installation of Recommends was disabled to build the images, they are still too big. This will need further tweaking as they are supposed to fit with the next beta.
  
  
• The rescue flavour, containing system rescue and forensic related packages, is missing in this beta release.
  
  
• There will be a DVD image with the next beta that includes all three desktop environments so that you can choose at boot time which system you would like to start.
  
  
• Due to time constraints, the prebuilt images for Beta1 are only covering i386 and amd64; with the next beta, powerpc and sparc will follow (if you wish to test these architectures earlier, please build them yourself).
  
  
• The new desktop artwork is not yet included.
  
  
• The syslinux menu is still the old, prompt-based one. A freshly made new syslinux vgamenu using the official lenny desktop artwork is on the way (the same as d-i media will use in Lenny).
  
  
• No live-installer included yet (if you wish to test live-installer earlier, please build it yourself).
  
  
• No win32-loader included yet.
  
  
• Sid packages used - At the time of building the live images, both live-helper 1.0.0-1 and live-initramfs 1.139.1-1 from sid were used. Since the latter has not yet migrated to testing, it was included manually as a local package. This is undesirable, as the release is supposed to be self-contained - however, it is just a convenient workaround as both were granted freeze exception and will migrate soon.

Plans for next Beta release We are looking forward to upload Beta2 in about two weeks from now (maybefollowed by a third beta) with one final RC after that which should be identical to the final release. Some more details about the open things we would like to address in Beta2 and later can be found at the wiki page. The Debian Live team is still looking for more contributors for new features (post-lenny, though) as well as documentation writers for the manual (always). If you care about live systems, please join and help! Thanks Last but not least, our thanks goes to everyone who has contributed and to all maintainers that have kindly fixed live-specific bugs in their packages.

Russel Coker blogs about a problem, which concerned me as well: Killing Servers with Virtualisation and Swap, i.e.: what happens when one domU is happily swapping the whole day?

Luckily this didn't happen to me yet, but as Russel do I tend as well to give a small sized swap area to domUs. If they're doing extensive swapping, something is wrong and most probably a task has a memory leakiing problem or the virtual machine is undersized with its RAM.

Anyway, Russel had some thoughts and ideas how to deal with the problem, such as giving dedicated swap areas on single disks to some domUs to seperate disk I/O for the filesystem and the I/O for swap. He proceeds with:

Now if you have a server with 8 or 12 disks (both of which seem to be reasonably common capacities of modern 2RU servers) and if you decide that RAID is not required for the swap space of DomUs then it would be possible to assign single disks for swap spaces for groups of virtual machines. So if one client had several virtual machines they could have them share the same single disk for the swap, so a thrashing server would only affect the performance of other VMs from the same client. One possible configuration would be a 12 disk server that has a four disk RAID-5 array for main storage and 8 single disks for swap. 8 CPU cores is common for a modern 2RU server, so it would be possible to lock 8 groups of DomUs so that they share CPUs and swap spaces. Another possibility would be to have four groups of DomUs where each group had a RAID-1 array for swap and two CPU cores.

I would myself consider a different approach:

• make your RAID as usual across your 8 or 12 disks, but don't use the whole disks, but just a partition on it, leave 10 GB or so free on each disk for later swap purposes.


• with 10 GB on each disk you'll have 80 GB swap with 8 disks or 120 GB with 12 disks in your 2 RU server.


• you can setup your swap areas as needed. Maybe some domUs would benefit from more heads when swapping, some need more space or another one should survive when one disk fails. So you can setup each swap differently, be it as a single partition on a single disk or a RAID1 or JBOD for multiple heads.

Of course you can mix up both approaches or even use swap over NFS or NBD/DRBD. There are many ways and possible solutions, but the best way to deal with swapping is to take care that it doesn't happen, of course... ;)

The Problem: A problem with virtual machines is the fact that one rogue DomU can destroy the performance of all the others by inappropriate resource use. CPU scheduling is designed to allow reasonable sharing of computational resources, it is unfortunately not well documented, the XenSource wiki currently doesn’t document the “credit” scheduler which is used in Debian/Etch and CentOS 5 [1]. One interesting fact is that CPU scheduling in Xen can have a significant effect on IO performance as demonstrated in the paper by Ludmila Cherkasova, Diwaker Gupta and Amin Vahdat [2]. But they only showed a factor of two performance difference (which while bad is not THAT bad). A more significant problem is managing virtual memory, when there is excessive paging performance can drop by a factor of 100 and even the most basic tasks become impossible. The design of Xen is that every DomU is allocated some physical RAM and has it’s own swap space. I have previously written about my experiments to optimise swap usage on Xen systems by using a tmpfs in the Dom0 [3]. The aim was to have every Xen DomU swap data out to a tmpfs so that if one DomU was paging heavily and the other DomUs were not paging then the paging might take place in the Dom0’s RAM and not hit disk. The experiments were not particularly successful but I would be interested in seeing further research in this area as there might be some potential to do some good. I have previously written about the issues related to swap space sizing on Linux [4]. My conclusion is that following the “twice RAM” myth will lead to systems becoming unusable due to excessive swapping in situations where they might otherwise be usable if the kernel killed some processes instead (naturally there are exceptions to my general rule due to different application memory use patterns - but I think that my general rule is a lot better than the “twice RAM” one). One thing that I didn’t consider at the time is the implications of this problem for Xen servers. If you have 10 physical machines and one starts paging excessively then you have one machine to reboot. If you have 10 Xen DomUs on a single host and one starts paging heavily then you end up with one machine that is unusable due to thrashing and nine machines that deliver very poor disk read performance - which might make them unusable too. Read performance can particularly suffer in a situation when one process or VM is writing heavily to disk due to the way that the disk queuing works, it’s not uncommon for an application to read dozens or hundreds of blocks from disk to satisfy a single trivial request from a user, if each of these block read requests has to wait for a large amount of data to be written out from the write-back cache then performance will suck badly (I have seen this in experiments on single disks and on Linux software RAID - but have not had the opportunity to do good tests on a hardware RAID array). Currently for Xen DomUs I am allocating swap spaces no larger than 512M, as anything larger than that is likely to cause excessive performance loss to the rest of the server if it is actually used. A Solution for Similar Problems: A well known optimisation technique of desktop systems is to use a separate disk for swap, in desktop machines people often use the old disk as swap after buying a new larger disk for main storage. The benefit of this is that swap use will not interfere with other disk use, for example the disk reads needed to run the “ps” and “kill” programs won’t be blocked by the memory hog that you want to kill. I believe that similar techniques can be applied to Xen servers and give even greater benefits. When a desktop machine starts paging excessively the user will eventually take a coffee break and let the machine recover, but when an Internet server such as a web server starts paging excessively the requests keep coming in and the number of active processes increases so it seems likely that using a different device for the swap will allow some processes to satisfy requests by reading data from disk while some other processes are waiting to be paged in. Applying it to Xen Servers: The first thing that needs to be considered for such a design is the importance of reliable swap. When it comes to low-end servers there is ongoing discussion about the relative merits of RAID-0 and RAID-1 for swap. The benefit of RAID-0 is performance (at least in perception - I can imagine some OS swapping algorithms that could potentially give better performance on RAID-1 and I am not aware of any research in this area). The benefit of RAID-1 is reliability. Now there are two issues in regard to reliability, one is continuity of service (EG being able to hot-swap a failed disk while the server is running), and the other is the absence of data loss. For some systems it may be acceptable to have a process SEGV (which I presume is the result if a page-in request fails) due to a dead disk (reserving the data loss protection of RAID for files). One issue related to this is the ability to regain control of a server after a problem. For example if the host OS of a machine had non-RAID swap then a disk failure could prevent a page-in of data related to sshd or some similar process and thus make it impossible to recover the machine without hardware access. But if the swap for a virtual machine was on a non-RAID disk and the host had RAID for it’s swap then the sysadmin could login to the host and reboot the DomU after creating a new swap space on a working disk. Now if you have a server with 8 or 12 disks (both of which seem to be reasonably common capacities of modern 2RU servers) and if you decide that RAID is not required for the swap space of DomUs then it would be possible to assign single disks for swap spaces for groups of virtual machines. So if one client had several virtual machines they could have them share the same single disk for the swap, so a thrashing server would only affect the performance of other VMs from the same client. One possible configuration would be a 12 disk server that has a four disk RAID-5 array for main storage and 8 single disks for swap. 8 CPU cores is common for a modern 2RU server, so it would be possible to lock 8 groups of DomUs so that they share CPUs and swap spaces. Another possibility would be to have four groups of DomUs where each group had a RAID-1 array for swap and two CPU cores. I am not sure of the aggregate performance impact of such a configuration, I suspect that a group of single disks would give better performance for swap than a single RAID array and that RAID-1 would outperform RAID-5. For a single DomU it seems most likely that using part of a large RAID array for swap space would give better performance. But the benefit in partitioning the server seems clear. An architecture where each DomU had it’s own dedicated disk for a swap space is something that I would consider a significant benefit if renting a Xen DomU. I would rather have the risk of down-time (which should be short with hot-swap disks and hardware monitoring) in the rare case of a disk failure than have bad performance regularly in the common situation of someone else’s DomU being overloaded. Failing that, having a separate RAID array for swap would be a significant benefit. If every process that isn’t being paged out could deliver full performance while one DomU was thrashing then it would be a significant benefit over the situation where any DomU can thrash and kill the file access performance of all other DomUs. A single RAID-1 array should handle all the swap space requirements for a small or medium size Xen server One thing that I have not tested is the operation of LVM when one disk goes bad. In the case of a disk with bad sectors it’s possible to move the LVs that are not affected to other disks and to remove the LV that was affected and re-create it after removing the bad disk. The case of a disk that is totally dead (IE the PV header can’t be read or written) might cause some additional complications.

• [1] http://wiki.xensource.com/xenwiki/Scheduling


• [2] http://www.cs.ucsd.edu/~dgupta/papers/per07-3sched-xen.pdf


• [3] http://etbe.coker.com.au/2008/05/22/xen-and-swap/


• [4] http://etbe.coker.com.au/2007/09/28/swap-space/

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Rhonda, have you reported the SCons problems you’ve found to either the Debian mantainer or upstream? That’s much more likely to be an effective way of improving things than blogging about them. For what it’s worth the .scons files are a bug in the SCons core AFAICT (it needs a distclean equivalent that doesn’t appear to be there; I suspect nobody has asked for it before) and the failure to clean up other generated files will be bugs in the support for whatever tool is being used to do the build.

How to read the Freerunner's accelerometers This code has been take from moko_eightball by Jakob Westhoff: it just continuously prints the value of the three accelerometers.

The Linux kernel has a number of code sections which look at the apparent size of the machine and determine what would be the best size for buffers. For physical hardware this makes sense as the hardware doesn’t change at runtime. There are many situations where performance can be improved by using more memory for buffers, enabling large buffers for those situations when the machine has a lot of memory makes it convenient for the sysadmin. Virtual machines change things as the memory available to the kernel may change at run-time. For Xen the most common case is the Dom0 automatically shrinking when memory is taken by a DomU - but it also supports removing memory from a DomU via the xm mem-set command (the use of xm mem-set seems very rare). Now a server that is purchased for the purpose of running Xen will have a moderate amount of RAM. In recent times the smallest machine I’ve seen purchased for running Xen had 4G of RAM - and it has spare DIMM slots for another 4G if necessary. While a non-virtual server with 8G of RAM would be an unusually powerful machine dedicated for some demanding application, a Xen server with 8G or 16G of RAM is not excessively big, it’s merely got space for more DomU’s. For example one of my Xen servers has 8 CPU cores, 8G of RAM, and 14 DomUs. Each DomU has on average just over half a gig of RAM and half of a CPU core - not particularly big. In a default configuration the Dom0 will start by using all the RAM in the machine, which in this case meant that the buffer sizes were appropriate for a machine with 8G of RAM. Then as DomUs are started memory is removed from the Dom0 and these buffers become a problem. This ended up forcing a reboot of the machine by preventing Xen virtual network access to most of the DomUs. I was seeing many messages in the Dom0 kernel message log such as “xen_net: Memory squeeze in netback driver” and most DomUs were inaccessible from the Internet (I didn’t verify that all DomUs were partially or fully unavailable or test the back-end network as I was in a hurry to shut it down and reboot before too many customers complained). The solution to this is to have the Dom0 start by using a small amount of RAM. To do this I edited the GRUB configuration file and put “dom0_mem=256000” at the end of the Xen kernel line (that is the line starting with “kernel /xen.gz“). This gives the Dom0 kernel just under 256M of RAM from when it is first loaded and prevents allocation of bad buffer sizes, it’s the only solution to this network problem that a quick Google search (the kind you do when trying to fix a serious outage before your client notices (*)) could find. One thing to note is that my belief that it’s kernel buffer sizes that are at the root cause of this problem is based on my knowledge of how some of the buffers are allocated plus an observation of the symptoms. I don’t have a test machine with anything near 8G of RAM so I really can’t do anything more to track this down. There is another benefit to limiting the Dom0 memory, I have found that on smaller machines it’s impossible to reduce the Dom0 memory below a certain limit at run-time. In the past I’ve had problems in reducing the memory of a Dom0 below about 250M, while such a reduction is hardly desirable on a machine with 8G of RAM, when running an old P3 machine with 512M of RAM there are serious benefits to making Dom0 smaller than that. As a general rule I recommend having a limit on the memory of the Dom0 on all Xen servers. If you use the model of having no services running on the Dom0 there is no benefit in having much ram assigned to it. (*) Hiding problems from a client is a bad idea and is not something I recommend. But being able to fix a problem and then tell the client that it’s already fixed is much better than having them call you when you don’t know how long the fix will take.

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Polysms Here is my first software designed for the FreeRunner: polysms. It's a commandline tool: you pass it a polygen grammar name and a phone number, and it will send a SMS to that phone number using the polygen output for that grammar as the SMS text:

# polyrun manager 0012345678

And here is the code, that works on the http://www.freesmartphone.org dbus framework:

I took a note of the various talks I attended at DebConf, with the aim of writing a few notes about each so that I could try to explain to my work mates exactly what I get out of going. However I think a lot of the benefit is about general face to face contact with fellow DDs and random conversations that happen. Having worked from home for over 3 years I'm finding it quite nice to be back in an office with people working on the same things as me; there are conversations that you will have over a quick cup of coffee or in the corridor that you wouldn't bother typing on IRC or email or picking up the phone for. Debian is a lot like a large organisation full of telecommuters and DebConf provides a vital opportunity for us to have those "minor" conversations that prove quite useful and to remind each other what we're actually like in person. I didn't end up writing a lot of notes during the talks so these are just snippets after the fact. If I'd been more organised I'd have done a write up on a daily basis rather than leaving it all until the week after. A lot of the below is fragmented thoughts, but the longer I leave it the less relevant it gets and the more chance I forget something. It'd have been up faster if I hadn't been fighting Movable Type to try and get some sort of headings. Sunday
Introduction, Marga The "Welcome to DebConf" bit. Marga got up and talked about how at DebConf4 (Brazil) she hadn't been a DD and now she was and how it had been a life changing event. She'd thought she was to blame for DebConf8 in Argentina, but trawling mail archives had shown it was originally Mart n's idea. She hadn't realised at the start quite how much work it would be. Steve's DPL talk, Steve McIntyre The DPL welcomes us to DebConf and talks about Debian's achievements, some of the results of his team survey (the teams largely say they need more manpower. Not really a huge surprise.). NM/User Survey BOF, Paul Wise Paul emailed debian-user, debian-newmaint and various other places (I think) asking about people's experiences as a Debian user or applicant to New Maint. His final results aren't yet published and I got the impression a disappointing number of our users had replied. The NM problems these days seem to be largely down to a lack of AMs, at least according to the stats on nm.debian.org. Meet SPI board - bdale, maulkin, jimmy, michael, others A chance to meet those of the SPI board who were present. The usual "If you're involved with Debian you should seriously consider joining SPI". Some discussion about the fact that although SPI was originally mostly Debian these days other projects are making more and more use of it - OFTC, PostgreSQL and Madwifi for example. Not a huge amount of new information for me. I've been an SPI member for some time and I think they perform a vital role for Debian. They've had issues in the past but it's really good to see them overcome and more projects on board. Monday
http://hp.com/go/debian, bdale Bdale talks about the history of Debian and HP. And makes the point that HP aren't doing any of this to be "nice"; their primary responsibility is to their shareholders. Not surprising, but it's good that even with that criteria at the fore front Debian ends up a good idea for a large multinational. Managing 666 packages, Mart n Ferrari Mostly centered around the pkg-perl experience and the tools/workflow they have to help manage things. Impressive web tool (DEHS) to help track packages with new upstreams, issues or pending uploads. Quality Assurance in Lenny + 1 I can't remember a lot of this, which is a bit bad. I remember a discussion about whether we should release with orphaned packages, or if they should be removed. The argument for not removing them seemed to revolve around a theory that if they weren't buggy then what was the harm, the argument for was that if they were unmaintained and not really used than how did we actually know they weren't buggy, and was it reasonable that they potentially held up library transitions etc? Bugs in large packages Don Armstrong and ways in which the BTS can help people with lots of bugs. This (thankfully) doesn't affect me, but it was interesting to hear Don talk about his work on the BTS and his various ideas. I was sorry I'd missed his talk on SOAP access to it; I shall have to find time to watch the video. Tuesday
Debian and Ubuntu, Mark Shuttleworth The usual interaction with Debian stuff, including how we interact with our upstreams. If a bug is raised with an Ubuntu package then it might well be appropriate to raise it with Debian and upstream as well, but each set of people should be able to use their own bug reporting systems rather than having to go to a foreign system. I don't think it was actually said, but I guess the idea is that launchpad is the thing that will do this gluing together. He also talked about Ubuntu as an "experiment" rather than a fork of Debian; something that has potentially different ideas about how to do things but that these ideas may lead to things that should be fed back into Debian. The point was made that even if you consider Ubuntu a fork they've forked 9 times now; it hasn't been a case of forking once and diverging wildly since thast point. I have a few thoughts on all the whole Debian/Ubuntu stuff which I should really try to form into something coherant and post. I think it's important to take Mark's talk in the context of bdale's "Shareholders come first" point. Derivatives round table Didn't stay for most of this. Ubuntu, Debian-EDU (which I hadn't realised was a derivative rather than a team within Debian, but apparently there are various things it was much easier for them just to patch now and try to work towards a generic solution later), someone from Extramadura and someone from the Munich government Linux stuff. I'm sure I've missed someone off. tdebs/i18n This was a useful BOF. It helped that we said no to the usual video team requirement that if you want to speak you had to wait for the microphone. This works fine for a normal talk, but really impedes the flow of conversation in something like a BOF. tdebs are something that have partly come from a need of Emdebian to reduce installed package size and partly from the desire of the i18n team to be able to update package translations without having to do a full binary NMU of a package. We had some of the FTP team, the release team, the i18n team and Emdebian there and I think some progress has been made. There'd been various conversations had before this meeting which I think helped people think about the issues and objections so that we had answers by the time we all sat down together - an excellent example of the use of DebConf. DebConf9 C ceres Various bits of discussion about next year's DebConf in Extramadura. Temperature is likely to be an issue for me as they reckon it could easily get up to 40C! I'll melt! Venue sounds good; some queries regarding late night hacklabs and net connections to same, but I'm sure the networking team will sort it all out as usual. ;) DebConf10 bids Venezela and New York were both pitching. Lots of people don't want to travel to the US or think they'll have problems doing so (I hadn't realised there was such an issue for people from South America). I suspect various people will have issues with Venezela as well; I heard expressions of doubt over their political stability expressed. However I'd be happy to go to either (and preferably both! DebConf10 + 12 perhaps?) Speaking of which, what ever happened to the Sarajevo bid? If they're reading, have you considered DebConf11? Wednesday
A day trip to an Argentinian ranch and lunch was an asido. Fantastic food and a pleasant afternoon spent sitting in the sun chatting to people. That evening was the formal, but thanks to having stayed up until after 4 on Tuesday I had to wimp out and go to bed fairly early. Not until I'd seen the DPL dance though. :) Thursday
Internationalization in Debian I forget most of this other than pretty graphs from Christian regarding what's translated and what other languages we might have; e.g. you can consider South America to be covered largely by Spanish and Portuguese, or you can consider it to not be covered very much at all by the local indigenous languages. dh-make-webapp: yeah right! Mainly what I took away from this was "It'll never happen thanks to the fact that every web app author uses a different system" and that more work needs to be done on the web apps best practices document. I don't really do web apps, but having them easily installable on my systems is a good thing so I hope some standardisation within Debian comes from this. Best practises in team-maintaining packages Various team members got up to talk about work flow in their teams. Not unsurprisingly different things seem to work for different people. Predictable PRNG in the Vulnerable Debian OpenSSL Package Lucian giving his Black Hat talk about the OpenSSL issues we faced earlier this year. Some queries about automated testing and that it should have found this, which originally I agreed with until I thought about it - you'd have to have run > 65536 tests and compared all the data to find this; something like the FIPS tests against a single run wouldn't have shown any issues. Lucian wanted feedback on ensuring he was presenting the Debian side of things acceptably as well. Keysigning Run by Don Armstrong. Nothing to really remark except I think key signing attendance is dropping off after things like the Helsinki experience. Also I've now managed to get my new RSA key signed by keys other than my own (and I'll try to get sorted out to sign keys myself soon). Friday
LessWatts Intel's drive towards reducing power usage. Odd to hear such things from someone who wasn't Matthew Garrett and I think I'd heard most of it before. Debian technical policy update Sorry Manoj, I should have been paying more attention. Debian Policy is something I think is important, but I'm not enough of a nitpicker to really feel I can contribute a whole lot. Virtualisation in Debian - Present and future This was depressing. What I took away was "We had 2 forms of virtualisation in etch (Xen + vserver) and we're supporting neither for Lenny". As someone running a Xen machine this is problematic. The host does have the hardware support that would allow kvm, but I'm worried about smooth migration (it's a colo box). There was some mention of Xenner, which isn't packaged for Debian. I took a look at doing so but there are some worrying items in the TODO list (like, oh, locking to enable reliable SMP) and I've spectacularly failed to get it compiling so far. I should have another go. Emdebian update Neil Williams about where Emdebian is and waved his Balloon3 about. Some interest from the Openmoko guys and discussion about why it might be better than OpenEmbedded. And equally what it couldn't do that OpenEmbedded can manage (mainly very small installs; a minimal Emdebian install is 24MB+ and with X that goes up to 75MB+ I believe). netconf I'd never actually seen Martin talk about netconf before. Am impressive flow of control diagram. It all sounds quite complex for little benefit at present, but if he pulls it off then I can see it being a much more flexible replacement for the likes of Network Manager. Saturday
Lenny - The Road To Release Neil played with putting the heads of the release team on random images. And tried to tell us all how to behave during the release process in terms of what should and shouldn't be uploaded etc. Most of it is just common sense, but apparently everything he talked about he'd experienced. Also pointed out we were supposed to release in 3 weeks and didn't even have the appropriate kernel in testing yet so it's probably not going to happen. Colour me surprised. Sustainable Computing Low power consumption/affordable computing. Interesting points about the OLPC being used in the middle of nowhere with no chance of an Internet connection being close by compared to neighbours in large cities where people can't necessarily afford top of the line computers or individual connections - in this sort of scenario mesh networking is really viable in terms of getting people connected up. Multi winner voting Manoj needs pretty diagrams, probably drawn by Martin Krafft. ;) Semi-interesting discussion about multi-winner voting (e.g. SPI board elections) and how the current Debian voting system is completely tied to Debian's infrastructure eg the LDAP setup. Manoj would like to make it more generic so it could be used by other groups as well as for different sorts of votes in Debian.

I recently wrote about wanting to have a teletype. Well, I have since realized that teletypes weigh hundreds of pounds, draw hundreds of watts, and aren't available on eBay for a reasonable price. Well I knew the hundreds of pounds bit, but still. I pretty well have had to give up on a real teletype.

So, now on to the next best thing: a teletype simulator. Enter the two free dot-matrix printers that found their way to my office earlier this week. One of them even works. I bicycled to the awesome local office supplies store (about 11 miles away) to buy a ribbon for it. This is the place that's been there since the 1890s. They still stock dot matrix ribbons, typewriter ribbons, and even fanfold paper.

On the project. Linux has its heritage in Unix, which was used with these devices. It can be made to work with them even now. But there's a trick: teletypes used a bidirectional serial link. Dot matrix printers have no keyboard. So we have to take input from a different device than we send output to.

A simple trick will do for that:

TERM=escpterm telnet localhost > /dev/lp0

Now, here's the next problem. Dot-matrix printers have a line buffer. They don't start printing the line at all until they see CR or LF. Makes it annoying for interactive use. So I wrote a quick tool to insert into that pipeline. After a certain timeout after the input stops, it will force the printer to flush its buffer. Took a little while to figure out how to do that, too; turns out there's a command ESC J that takes an increment for vertical spacing in 1/216 inch, and accepts 0. So I can send \x1BJ\x00 to flush the buffer. I can run it like this:

TERM=escpterm telnet localhost escpbuf > /dev/lp0

That leaves another problem, though: the printhead is right over the text. (Even though it moves to the right of the printing position, and then moves back left for the next character to print.) I modified the program to roll the paper out a bit, and then reverse feed it to continue printing the line. But that is slow and, I suspect, tough on the stepper motor.

Also, I have crafted a terminfo file for the Epson-compatible dot-matrix printers (which are almost all of them), which can also be found at the above link.

So here's the question, for anyone that has used a real teletype:

Did the printhead obscure the text there too, or could you see the entire current line at all times?

I’ve just read an amusing series of blog posts about bad wiring [1]. I’ve seen my share of wiring horror in the past. There are some easy ways of minimising wiring problems which seem to never get implemented. The first thing to do is to have switches near computers. Having 48 port switches in a server room and wires going across the building causes mess and is difficult to manage. A desktop machine doesn’t need a dedicated Gig-E (or even 100baseT) connection to the network backbone. Cheap desktop switches installed on desks allow one cable to go to each group of desks (or two cables if you have separate networks for VOIP and data). If you have a large office area then a fast switch in the corner of the room connecting to desktop switches on the desks is a good way to reduce the cabling requirements. The only potential down-side is that some switches are noisy, the switches with big fans can be easily eliminated by a casual examination, but the ones that make whistling sounds from the PSU need to be tested first. The staff at your local electronics store should be very happy to open one item for inspection and plug it in if you are about to purchase a moderate number (they will usually do so even if you are buying a single item). A common objection to this is the perceived lack of reliability of desktop switches. One mitigating factor is that if a spare switch is available the people who work in the area can replace a broken switch. Another is that my observation is that misconfiguration on big expensive switches causes significantly more down-time than hardware failures on cheap switches ever could. A cheap switch that needs to be power-cycled once a month will cause little interruption to work, while a big expensive switch (which can only be configured by the “network experts” - not regular sysadmins such as me) can easily cause an hour of down-time for most of an office during peak hours. Finally the reliability of the cables themselves is also an issue, having two cables running to the local switch in every office can allow an easy replacement to fix a problem - it can be done without involving the IT department (who just make sure that both cables are connected to the switch in the server room). If there is exactly one cable running to each PC from the server room and one of the cables fails then someone’s PC will be offline for a while. In server rooms the typical size of a rack is 42RU (42 Rack Units). If using 1RU servers that means 42 Ethernet cables. A single switch can handle 48 Ethernet ports in a 1RU mount (for the more dense switches), others have 24 ports or less. So a single rack can handle 41 small servers and a switch with 48 ports (two ports to go to the upstream switch and five spare ports). If using 2RU servers a single rack could handle 20 servers and a 24port switch that has two connections to the upstream switch and two spare ports. Also it’s generally desirable to have at least two Ethernet connections to each server (public addresses and private addresses for connecting to databases and management). For 1RU servers you could have two 48 port switches and 40 servers in a rack. For 2RU servers you could have 20 servers and either two 24port switches or one 48port switch that supports VLANs (I prefer two switches - it’s more difficult to mess things up when there are two switches, if one switch fails you can login via the other switch to probe it, and it’s also cheaper). If the majority of Ethernet cables are terminated in the same rack it’s much harder for things to get messed up. Also it’s very important to leave some spare switch ports available as it’s a common occurrence for people to bring laptops into a server room to diagnose problems and you really don’t want them to unplug server A to diagnose a problem with server B… Switches should go in the middle of the rack. While it may look nicer to have the switch at the top or the bottom, that means that the server which is above or below it will have the cables for all the other switches going past it. Ideally the cables would go in neat cable runs at the side of the rack but in my experience they usually end up just dangling in front. If the patch cables are reasonably short and they only dangle across half the servers things won’t get too ugly (this is harm minimisation in server room design). The low end of network requirements is usually the home office. My approach to network design for my home office is quite different, I have no switches! I bought a bunch of dual-port Ethernet cards and now every machine that I own has at least two Ethernet ports (and some have as many as four). My main router and gateway has four ports which allows connections from all parts of my house. Then every desktop machine has at least two ports so that I can connect a laptop in any part of the house. This avoids the energy use of switches (I previously used a 24 port switch that drew 45W [2]), switches of course also make some noise and are an extra point of failure. While switches are more reliable than PCs, as I have to fix any PC that breaks anyway my overall network reliability is increased by not using switches. For connecting the machines in my home I mostly use bridging (only the Internet gateway acts as a router), I have STP enabled on all machines that have any risk of having their ports cross connected but disable it on some desktop machines with two ports (so that I can plug my EeePC in and quickly start work for small tasks).

• [1] http://www.darkroastedblend.com/2008/08/crazy-wiring-part-5.html


• [2] http://doc.coker.com.au/environment/computer-related-power-use/

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According to a recent article, 6 Common Website Mistakes That Cost Money are:

1. JavaScript or other crawler-unfriendly navigation that may impede indexing

This one is best avoided at design-time, by including Web Content Accessibility Guidelines 1.0 Level A in the design brief, but if you’ve ended up with JavaScript-based navigation on your site (check by doing “View Source” and searching for the code for your home page link and so on - if you can find it, then it’s probably not javascript) and it’s based on some template system, a webmaster can probably do a whole-site edit to put the navigation links in the page properly - or at least add a useful <noscript> tag.

2. Navigation that buries important pages within the site architecture.

The structure of the website’s files and the structure of the link menus do not need to match, so if there’s a page that you feel is important, get your webmaster to add it to the navigation links across the whole site.

3. Duplicate “pages” getting indexed under multiple URLs.

This usually happens for one of two reasons: one is inappropriately-parked domains, which is mistake 6 below and often fairly easy to fix; the other is a misbehaving web application, which you’ll need to get a programmer to fix. You can do a simple test of your web application by starting at your homepage and following links to a particular page; then open a new browser window and try to reach the same page by different links (or a site search) and compare the address bars (the bit of your browser showing http://) - do they match? If not, you’ve got this problem.

4. No keyword phrase focus in the content or conversely, keyword phrase stuffing

You can use a good word-counter on the text to see how common different keywords and keyphrases, or use the “webmaster tools” section of some search engines to see what they’re focusing on. Keyword-stuffing can be fairly easy to see. If you “View Source” on a page and there’s a large block of keyword-intensive text somewhere in it that doesn’t appear it when viewed in a browser, then it’s probably stuffing. Many sites regard stuffing as a sort of spam, so you don’t want to be found doing this. To fix these problems, rewrite the page text appropriately.

5. An optimized home page, but that’s it

Repeat your checks from problem 4 on a few pages other than the home page to discover whether you suffer from this. Also, see whether your website statistics show search engine visitors arriving at a variety of different pages (these are sometimes called “Entry Page” statistics).

6. Additional domains owned by the company are not properly redirected

If you usually use .co.uk, but you also have a .com domain, try visiting a random page on your website, then click in the address bar and replace the .co.uk with .com - what happens? If the page is Not Found, then your domains aren’t properly redirected and you need a Redirect adding to the second one. If the page displays but the address doesn’t change itself back, then your domains are probably pointing at the same webspace but aren’t properly redirected, which will mean you’re probably making mistake 3 above. Usually, the simplest way to fix this is with a conditional redirect. On Apache webservers, you can add a .htaccess file containing something like:-

RewriteEngine On
RewriteCond % HTTP_HOST  !^www\.yourdomain\.co\.uk$ [NC]
RewriteRule (.*) http://www.yourdomain.co.uk/$1 [R=permanent,L]

That even works on BT Business web hosting, by the way. If it doesn’t work, try asking your web hosting provider to enable mod_rewrite for you or ask them to suggest how to achieve the same result.

The above list of mistakes was published on Search Engine Land last week. The correction methods are all things used by my webmaster cooperative.

I had a problem where the email address circsales@washpost.com spammed a Request Tracker (RT) [1] installation (one of the rules for running a vaction program is that you never respond twice to the same address, another rule is that you never respond to automatically generated messages). Deleting these tickets was not easy, the RT web interface only supports deleting 50 tickets at a time. To delete them I first had to find the account ID in RT, the following query does that:
select id from Users where EmailAddress='circsales@washpost.com'; Then to mark the tickets as deleted I ran the following SQL command (where X was the ID):
update Tickets set Status='deleted' where Creator=X; Finally to purge the deleted entries from the database (which was growing overly large) I used the RTx-Shredder [2] tool. RTx-Shredder doesn’t seem to support deleting tickets based on submitter, which is why I had to delete them first. I am currently using the following command to purge the tickets. The “limit,500” directive tells rtx-shredder to remove 500 tickets at one time (the default is to only remove 10 tickets).
./sbin/rtx-shredder --force --plugin 'Tickets=status,deleted;limit,500' There are currently over 34,000 deleted tickets to remove, and rtx-shredder is currently proceeding at a rate of 9 tickets per minute, so it seems that it will take almost three days of database activity to clear the tickets out. I also need to purge some tickets that have been resolved for a long time, I’m running the following command to remove them:
./sbin/rtx-shredder --force --plugin 'Tickets=status,resolved;updated_before,2008-03-01 01:01:34;limit,500' With both the rtx-shredder commands running at once I’m getting a rate of 15 tickets per minute, so it seems that the bottleneck is more related to rtx-shredder than MySQL (which is what I expected). Although with two copies running at once I have mysqld listed as taking about 190% of CPU (two CPUs running two capacity). The machine in question has two P4 CPUs with hyper-threading enabled, so maybe running two copies of rtx-shredder causes mysqld to become CPU bottlenecked. I’m not sure how to match up CPU use as reported via top to actual CPU power in a system with hyper-threading (the hyper-threaded virtual CPUs do not double the CPU power). I wonder if this means that the indexes on the RT tables are inadequate to the task. I tried adding the following indexes (as suggested in the rtx-shredder documentation), but it didn’t seem to do any good - it might have improved performance by 10% but that could be due to sampling error. CREATE INDEX SHREDDER_CGM1 ON CachedGroupMembers(MemberId, GroupId, Disabled);
CREATE INDEX SHREDDER_CGM2 ON CachedGroupMembers(ImmediateParentId, MemberId);
CREATE UNIQUE INDEX SHREDDER_GM1 ON GroupMembers(MemberId, GroupId);
CREATE INDEX SHREDDER_TXN1 ON Transactions(ReferenceType, OldReference);
CREATE INDEX SHREDDER_TXN2 ON Transactions(ReferenceType, NewReference);
CREATE INDEX SHREDDER_TXN3 ON Transactions(Type, OldValue);
CREATE INDEX SHREDDER_TXN4 ON Transactions(Type, NewValue);

• [1] http://bestpractical.com/rt


• [2] http://search.cpan.org/~ruz/RTx-Shredder-0.07/

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I had a small chuckle at the delay to Debian Project news because the listserver filter treated it as if an event was on Free Ando Penis Land. Parties in Scunthorpe and Penistone may have a similar problem. At least it got through eventually. If only Yahoo was as responsive as debian listmasters… Incidentally, while trying a web search for “the Scunthorpe Problem”, I got an intermediate screen warning me that the results may contain “adult content” but none of the results looked like they were more than 18 years old.

John Goerzen writes an entertaining piece on his ongoing battle with Dell to stop receiving advertising from them. (The comments on the post are rather interesting in themselves) I say "good on you, John" for taking a stand. Now that I know of these prohibitory orders, I might try them out on Pennysaver so I stop getting their stupid catalogs. A while ago our junk mail situation got completely out of hand, and at the time I found 41pounds.org, which for a very reasonable $41, did a very good job of stopping pretty much all of the addressed spam. About the only thing we get now is a small wad of catalogs that USPS delivers to every resident, which isn't explicitly address to us by name, just the apartment number. That and these stupid "checks" from Washington Mutual that we can use against our credit card account with them. They give me the screaming heebie jeebies, and I shred them on sight, because I've seen how insecure cheques are.