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Swap Breaking SSD

I’ve seen many comments about swap space and SSD claiming that swap will inherently destroy SSD through using too many writes. The latest was in the comments of my post about swap space and SSD performance [1]. Note that I’m not criticising the person who commented on my blog, everyone has heard lots of reports about possible problems that they avoid without analysing them in detail.

The first thing to note is that the quality of flash memory varies a lot, the chips that are used in SSDs for workstation/server use are designed to last while those in USB-flash devices aren’t. I’ve documented my unsuccessful experiments with using USB-flash for the root filesystem of a gateway server [2] (and the flash device that wasn’t used for swap died too).

The real issue when determining whether swap will break your SSD is the amount of writes. While swapping can do a lot of writing quickly that usually doesn’t happen unless something has gone wrong. The workstation that I’m currently using has writes to the root fileystem outnumbering writes to swap by a factor of 130:1 (by volume of data written). On other days I’ve seen it as low as 42:1, in either case it’s writes to the root filesystem (which is BTRFS and includes /home etc) that will break the SSD if anything. For some other workstations I run I see ratios of 201:1 (that’s with 8G of RAM), 57:1, and 23:1. In a quick search I couldn’t find a single system I run where even 10% of disk writes were attributed to swap. This really isn’t surprising given that adding RAM is a cheap way to improve the performance of most systems. If a SSD didn’t do any write leveling (as is rumored to be the case with cheap USB flash devices) then swap use might still cause a problem because of the number of writes in a small area, but if that was the case then filesystem journals and other fixed data structures would be more likely to cause a problem – and any swap based breakage would break swap not the root filesystem (although if swap was the first partition then it might also break the MBR).

Of the workstations that are convenient to inspect the one with the most writes to the root filesystem and swap space (IE everything on /dev/sda) had 128G written per day for 1.2 days of uptime, but that involved running a filesystem balance and some torrent downloads (not the typical use). Among the two systems which had been running for more than 48 hours with typical use the most writes was 24G in a day. If a SSD can sustain 10,000 writes per block (which is smaller than quoted by most flash manufacturers nowadays) and has perfect wear leveling (which is unlikely) then the system with a 120G SSD and 128G written in a day could continue like that for almost 10,000 days or 27 years – much longer than storage is expected to work or be useful. So for workstation use (where even 24G of writes per day probably counts as heavy use) a 120G SSD that can sustain 10,000 writes per block shouldn’t be at great risk of wearing out.

Conclusion

I believe that swap is much less likely to break SSDs than regular file access on every system with a reasonable amount of RAM. For systems which don’t have enough RAM you probably want the speed of SSD for swap space anyway in spite of the risks.

If wear leveling works as designed and the 10,000+ writes per block claims are accurate then SSDs will massively outlast their useful life. Long before they wear out they should be too small, too slow, and probably not compatible. 26 years ago I had a 5.25″ full height ST-506 disk in my desktop PC, it wouldn’t physically fit in most systems I own now (unless I removed the DVD drive), there is no possibility of buying a controller (I don’t own a system with an ISA bus), and that disk was too slow and small by today’s standards. A 27yo SSD isn’t going to be useful for anything, even for archive storage it’s no good as no-one has tested long term storage and data could decay before then.

BTRFS Status April 2014

Since my blog post about BTRFS in March [1] not much has changed for me. Until yesterday I was using 3.13 kernels on all my systems and dealing with the occasional kmail index file corruption problem.

Yesterday my main workstation ran out of disk space and went read-only. I started a BTRFS balance which didn’t seem to be doing any good because most of the space was actually in use so I deleted a bunch of snapshots. Then my X session aborted (some problem with KDE or the X server – I’ll never know as logs couldn’t be written to disk). I rebooted the system and had kernel threads go into infinite loops with repeated messages about a lack of response for 22 seconds (I should have photographed the screen). When it got into that state the ALT-Fn keys to change a virtual console sometimes worked but nothing else worked – the terminal usually didn’t respond to input.

To try and stop the kernel from entering an infinite loop on every boot that I used “rootflags=skip_balance” on the kernel command line to stop it from continuing the balance which made the system usable for a little longer, unfortunately the skip_balance mount option doesn’t permanently apply, the kernel will keep trying to balance the filesystem on every mount until a “btrfs balance cancel” operation succeeds. But my attempts to cancel the balance always failed.

When I booted my system with skip_balance it would sometimes free some space from the deleted snapshots, after two good runs I got to 17G free. But after that every time I rebooted it would report another Gig or two free (according to “btrfs filesystem df“) and then hang without committing the changes to disk.

I solved this problem by upgrading my USB rescue image to kernel 3.14 from Debian/Experimental and mounting the filesystem from the rescue image. After letting kernel 3.14 work on the filesystem for a while it was in a stage where I could use it with kernel 3.13 and then boot the system normally to upgrade it to kernel 3.14.

I had a minor extra complication due to the fact that I was running “apt-get dist-upgrade” at the time the filesystem went read-only do the dpkg records of which packages were installed were a bit messed up. But that was easy to fix by running a diff against /var/lib/dpkg/info on a recent snapshot. In retrospect I should have copied from an old snapshot of the root filesystem, but I fixed the problems faster than I could think of better ways to fix them.

When running a balance the system had a peak IO rate of about 30MB/s reads and 30MB/s writes. That compares to the maximum contiguous file IO speed of 260MB/s for reads and 320MB/s for writes. During that time it had about 50% CPU time used for my Q8400 quad-core CPU. So far the only tasks that I do regularly which have CPU speed as a significant bottleneck are BTRFS filesystem balancing and recoding MP4 files. Compiling hasn’t been an issue because recently I haven’t been compiling many programs that are particularly big.

Lessons Learned

I should photograph the screen regularly when doing things that won’t be logged, those kernel error messages might have been useful to me or someone else.

The fact that the only kernel that runs BTRFS the way I need comes from the Experimental repository in Debian stands in contrast to the recent kernel patch that stops describing BTRFS as experimental. While I have a high opinion of the people who provide support for the kernel in commercial distributions and their ability to back-port fixes from newer kernels I’m concerned about their decision to support BTRFS. I’m also dubious about whether we can offer BTRFS support in Debian/Jessie (the next version of Debian) without a significant warning. OTOH if you find yourself with a BTRFS system that isn’t working well you could always hire me to fix it. I accept payment via Paypal, bank transfer, or Bitcoin. If you want to pay me in Grange then I assure you I will never forget about it. ;)

I thought that I wouldn’t have CPU speed issues when I started using the AMD64 architecture, for most tasks that’s been the case. But for systems for which storage is important I’ll look at getting faster CPUs because of BTRFS. Using faster CPUs for storage isn’t that uncommon (I used to work for SGI and dealt with some significant CPU power used for file serving), but needing a fast quad-core CPU to drive a single SSD is a little disappointing. While recovery from file system corner cases isn’t going to be particularly common it’s something that you want completed quickly, for personal systems you want to be doing something else and for work systems you don’t want down-time.

The BTRFS problems with running out of disk space are really serious. It seems that even workstations used at home can’t survive without monitoring. For any other filesystem used at home you can just let it get full and then delete stuff.

Include “rootflags=skip_balance” in the boot loader configuration for every system with a BTRFS root filesystem and in the /etc/fstab for every non-root BTRFS filesystem. I haven’t yet encountered a single situation where continuing the balance did any good or when it didn’t do any harm.

Sociological Images 2014

White Trash

The above poster was on a bridge pylon in Flinders St in 2012. It’s interesting to see what the Fringe Festival people consider to be associated with “white trash”. They claim homophobia is a “white trash” thing however lower class people have little political power and the fact that we still don’t have marriage equality in Australia is clear evidence that homophobia is prevalent among powerful people.

Toys vs Fairies

Fairies look pretty while boys toys do things

I took the above photo at Costco in 2012. I think it’s worth noting the way that the Disney Fairies (all female and marketed to a female audience) are standing around looking pretty while the Toy Story characters (mostly male and marketed to a male audience) are running out to do things. Having those items side by side on the shelf was a clear example of a trend in toys towards girls being encouraged to be passive while boys are doing things. The Toy Story pack has one female character, so it could be interpreted as being aimed at both boys and girls. But even that interpretation doesn’t remove the clear gender difference.

It seems ironic to me that the descriptions on the boxes are “Read, Play, and Listen” for the Toy Story pack and “Read, Play, and Colour” on the Fairies pack. Colouring is more active than listening so the pictures don’t match the contents.

Make Up vs Tools

Girls chocolate is make-up and boys chocolate is tools

I took the above photo in an Aldi store in early 2013, today I was in Aldi and noticed that the same chocolate is still on sale. A clear and pointless gender difference. Rumor has it that some of the gender difference in kids clothing is so that a child can’t wear the clothes of an older sibling of different gender, but chocolate only gets eaten once so there is no reason for this.

Oath

The above poster was inside the male toilet at Melbourne University in 2013. It would probably be good to have something like that on display all the time instead of just for one event.

Locks

Locks with inscriptions on a bridge on the Yarra River in Melbourne

I took the above picture early this year, it shows hundreds of padlocks attached to a bridge across the Yarra River in Melbourne. Each padlock has a message written or inscribed in it, mostly declarations of love. I first noticed this last year, I’m not sure how long it’s been up. There was nothing formal about this (no signs about it), people just see it and decide that they want to add to it. I guess that the council cuts some of them off periodically as the number of locks doesn’t seem to be increasing much in recent times.

It would be interesting to do some research into how many locks are needed to start one of these. It would also be interesting to discover whether the nature of the inscriptions determines the speed at which it takes off, would a bunch of padlocks with messages like “I Love Linux” inspire others as well as messages declaring love for random people? All that is required is some old locks and an engraving tool.

I wonder what the social norm might be regarding messing with those locks. If I was to use those padlocks to practice the sport of lock-picking (which I learned when in Amsterdam) I wonder whether random bystanders would try to discourage me. It seems likely that picking the locks and taking them away would get a negative reaction but I wonder whether picking them one at a time and replacing them (or maybe moving them to another wire) would get a reaction.

Blackface for Schoolkids

teachers choice blackface and yellowface masks

A craft shop at the Highpoint shopping center in Melbourne is selling “Teacher’s Choice” brand “Multicultural Face Masks”. “Multicultural” is a well regarded term in education, teaching children about other cultures is a good concept but can be implemented really badly. When I was in high school the subject “Social Studies” seemed to have an approach of “look how weird people are in other places” instead of teaching the kids anything useful.

Sociological Images has an informative article on the Australian Hey Hey it’s Saturday blackface incident in 2009 [1].

The idea of these masks seems to involve students dressing up as caricatures of other races. The mask which looks like someone’s idea of a Geisha is an even bigger WTF, mixing what the package calls “culture” (really race) with sex work. When I visited Tokyo I got the impression that “French maids” fill a similar niche to Geisha for younger Japanese men and the “maid cafe” thing is really popular there. I think it’s interesting to consider the way that a French maid costume is regarded differently to a Geisha costume. I expect that “Teacher’s Choice” doesn’t sell French maid costumes.

Delicious Cow

picture of a bovine named Delicious

Usually meat is advertised in a way that minimises the connection to living animals. Often adverts just show cuts of meat and don’t make any mention of animals and when animals are shown they are in the distance. The above picture was on the wall at a Grill’d burger restaurant in Point Cook. It shows a bovine (looks like a bull even though I believe that cows are the ones that are usually eaten) with a name-tag identifying it as “Delicious”. The name tag personalises the animal which is an uncommon thing to do when parts of an animal are going to be eaten.

Of the animals that are commonly eaten it seems that the general trend is to only show fish as complete live animals, presumably because people can identify with mammals such as cattle in a way that they can’t identify with fish. Fish are also the only complete animals that are shown dead, adverts for fish that are sold as parts (EG salmon and tuna) often show complete dead fish. But I’ve never seen a meat advert that shows a complete dead cow or sheep.

Sociological Images 2012

In 2011 I wrote a post that was inspired by the Sociological Images blog [1]. After some delay here I’ve written another one. I plan to continue documenting such things.

Playground

gender segregated playground in 1918

In 2011 I photographed a plaque at Flagstaff Gardens in Melbourne. It shows a picture of the playground in 1918 with segregated boys and girls sections. It’s interesting that the only difference between the two sections is that the boys have horizontal bars and a trapeze. Do they still have gender segregated playgrounds anywhere in Australia? If so what is the difference in the sections?

Aborigines

The Android game Paradise Island [2] has a feature where you are supposed to stop Aborigines from stealing, it plays on the old racist stereotypes about Aborigines which are used to hide the historical record that it’s always been white people stealing from the people that they colonise.

Angry face icons over AboriginesAborigines described as thieves

There is also another picture showing the grass skirts. Nowadays the vast majority of Aborigines don’t wear such clothing, the only time they do is when doing some sort of historical presentation for tourists.

I took those pictures in 2012, but apparently the game hasn’t changed much since then.

Lemonade

lemonade flavored fizzy drink

Is lemonade a drink or a flavour? Most people at the party where I took the above photo regard lemonade as a drink and found the phrase “Lemonade Flavoured Soft Drink” strange when it was pointed out to them. Incidentally the drink on the right tastes a bit like the US version of lemonade (which is quite different from the Australian version). For US readers, the convention in Australia is that “lemonade” has no flavor of lemons.

Not Sweet

maybe gender queer people on bikes

In 2012 an apple cider company made a huge advertising campaign featuring people who might be gender queer, above is a picture of a bus stop poster and there were also TV ads. The adverts gave no information at all about what the drink might taste like apart from not being “as sweet as you think”. So it’s basically an advertising campaign with no substance other than a joke about people who don’t conform to gender norms.

Also it should be noted that some women naturally grow beards and have religious reasons for not shaving [3].

Episode 2 of the TV documentary series “Am I Normal” has an interesting interview of a woman with a beard.

Revolution

communist revolution Schweppes drinks

A violent political revolution is usually a bad thing, using such revolutions to advertise sugar drinks seems like a bad idea. But it seems particularly interesting to note the different attitudes to such things in various countries. In 2012 Schweppes in Australia ran a marketing campaign based on imagery related to a Communist revolution (the above photo was taken at Southern Cross station in Melbourne), I presume that Schweppes in the US didn’t run that campaign. I wonder whether global media will stop such things, presumably that campaign has the potential to do more harm in the US than good in Australia.

Racist Penis Size Joke at Southbank

racist advert in Southbank paper

The above advert was in a free newspaper at Southbank in 2012. Mini Movers thought that this advert was a good idea and so did the management of Southbank who approved the advert for their paper. Australia is so racist that people don’t even realise they are being racist.

Swap Space and SSD

In 2007 I wrote a blog post about swap space [1]. The main point of that article was to debunk the claim that Linux needs a swap space twice as large as main memory (in summary such advice is based on BSD Unix systems and has never applied to Linux and that most storage devices aren’t fast enough for large swap). That post was picked up by Barrapunto (Spanish Slashdot) and became one of the most popular posts I’ve written [2].

In the past 7 years things have changed. Back then 2G of RAM was still a reasonable amount and 4G was a lot for a desktop system or laptop. Now there are even phones with 3G of RAM, 4G is about the minimum for any new desktop or laptop, and desktop/laptop systems with 16G aren’t that uncommon. Another significant development is the use of SSDs which dramatically improve speed for some operations (mainly seeks).

As SATA SSDs for desktop use start at about $110 I think it’s safe to assume that everyone who wants a fast desktop system has one. As a major limiting factor in swap use is the seek performance of the storage the use of SSDs should allow greater swap use. My main desktop system has 4G of RAM (it’s an older Intel 64bit system and doesn’t support more) and has 4G of swap space on an Intel SSD. My work flow involves having dozens of Chromium tabs open at the same time, usually performance starts to drop when I get to about 3.5G of swap in use.

While SSD generally has excellent random IO performance the contiguous IO performance often isn’t much better than hard drives. My Intel SSDSC2CT12 300i 128G can do over 5000 random seeks per second but for sustained contiguous filesystem IO can only do 225M/s for writes and 274M/s for reads. The contiguous IO performance is less than twice as good as a cheap 3TB SATA disk. It also seems that the performance of SSDs aren’t as consistent as that of hard drives, when a hard drive delivers a certain level of performance then it can generally do so 24*7 but a SSD will sometimes reduce performance to move blocks around (the erase block size is usually a lot larger than the filesystem block size).

It’s obvious that SSDs allow significantly better swap performance and therefore make it viable to run a system with more swap in use but that doesn’t allow unlimited swap. Even when using programs like Chromium (which seems to allocate huge amounts of RAM that aren’t used much) it doesn’t seem viable to have swap be much bigger than 4G on a system with 4G of RAM. Now I could buy another SSD and use two swap spaces for double the overall throughput (which would still be cheaper than buying a PC that supports 8G of RAM), but that still wouldn’t solve all problems.

One issue I have been having on occasion is BTRFS failing to allocate kernel memory when managing snapshots. I’m not sure if this would be solved by adding more RAM as it could be an issue of RAM fragmentation – I won’t file a bug report about this until some of the other BTRFS bugs are fixed. Another problem I have had is when running Minecraft the driver for my ATI video card fails to allocate contiguous kernel memory, this is one that almost certainly wouldn’t be solved by just adding more swap – but might be solved if I tweaked the kernel to be more aggressive about swapping out data.

In 2007 when using hard drives for swap I found that the maximum space that could be used with reasonable performance for typical desktop operations was something less than 2G. Now with a SSD the limit for usable swap seems to be something like 4G on a system with 4G of RAM. On a system with only 2G of RAM that might allow the system to be usable with swap being twice as large as RAM, but with the amounts of RAM in modern PCs it seems that even SSD doesn’t allow using a swap space larger than RAM for typical use unless it’s being used for hibernation.

Conclusion

It seems that nothing has significantly changed in the last 7 years. We have more RAM, faster storage, and applications that are more memory hungry. The end result is that swap still isn’t very usable for anything other than hibernation if it’s larger than RAM.

It would be nice if application developers could stop increasing the use of RAM. Currently it seems that the RAM requirements for Linux desktop use are about 3 years behind the RAM requirements for Windows. This is convenient as a PC is fully depreciated according to the tax office after 3 years. This makes it easy to get 3 year old PCs cheaply (or sometimes for free as rubbish) which work really well for Linux. But it would be nice if we could be 4 or 5 years behind Windows in terms of hardware requirements to reduce the hardware requirements for Linux users even further.

Phone Based Lectures

Early this month at a LUV meeting I gave a talk with only my mobile phone to store notes. I used Google Keep to write the notes as it’s one of the easiest ways of writing a note on a PC and quickly transferring it to a phone – if I keep doing this I will find some suitable free software for this task. Owncloud seems promising [1], but at the moment I’m more concerned with people issues than software.

Over the years I’ve experimented with different ways of presenting lectures. I’m now working with the theory that presenting the same data twice (by speaking and text on a projector) distracts the audience and decreases learning.

Editing and Viewing Notes

Google Keep is adequate for maintaining notes, it’s based on notes that are a list of items (like a shopping list) which is fine for lecture notes. It probably has lots of other functionality but I don’t care much about that. Keep is really fast at updating notes, I can commit a change on my laptop and have it visible on my phone in a few seconds over 3G.

Most of the lectures that I’ve given have involved notes on a laptop. My first laptop was a Thinkpad 385XD with a 12.1″ display and all my subsequent laptops have had a bigger screen. When a laptop with a 12″ or larger screen is on a lectern I can see the notes at a glance without having to lean forward when 15 or fewer lines of text are displayed on the screen. 15 lines of text is about the maximum that can be displayed on a slide for the audience to read and with the width of a computer display or projector is enough for a reasonable quantity of text.

When I run Keep on my Galaxy Note 2 it displays about 20 rather short lines of text in a “portrait” orientation (5 points for a lecture) and 11 slightly longer lines in a “landscape” orientation (4 points). In both cases the amount of text displayed on a screen is less than that with a laptop while the font is a lot smaller. My aim is to use free software for everything, so when I replace Keep with Owncloud (or something similar) I will probably have some options for changing the font size. But that means having less than 5 points displayed on screen at a time and thus a change in the way I present my talks (I generally change the order of points based on how well the audience seem to get the concepts so seeing multiple points on screen at the same time is a benefit).

The Samsung Galaxy Note 2 has a 5.5″ display which is one of the largest displays available in a phone. The Sony Xperia X Ultra is one of the few larger phones with a 6.44″ display – that’s a large phone but still not nearly large enough to have more than a few points on screen with a font readable by someone with average vision while it rests on a lectern.

The most obvious solution to the problem of text size is to use a tablet. Modern 10″ tablets have resolutions ranging from 1920*1080 to 2560*1600 and should be more readable than the Thinkpad I used in 1998 which had a 12″ 800*600 display. Another possibility that I’m considering is using an old phone, a Samsung Galaxy S weighs 118 to 155 grams and is easier to hold up than a Galaxy Note 2 which weighs 180g. While 60g doesn’t seem like much difference if I’m going to hold a phone in front of me for most of an hour the smaller and lighter phone will be easier and maybe less distracting for the audience.

Distributing URLs

When I give a talk I often want to share the addresses of relevant web sites with the audience. When I give a talk with the traditional style lecture notes I just put the URLs on the final page (sometimes using tinyurl.com) for people to copy during question time. When I use a phone I have to find another way.

I did a test with QR code recognition and found that a code that takes up most of the width of the screen of my Galaxy Note 2 can be recognised by a Galaxy S at a distance of 50cm. If I ran the same software on a 10″ tablet then it would probably be readable at a distance of a meter, if I had the QR code take up the entire screen on a tablet it might be readable at 1.5m away, so it doesn’t seem plausible to hold up a tablet and allow even the first few rows of the audience to decode a QR code. Even if newer phones have better photographic capabilities than the Galaxy S that I had available for testing there are still lots of people using old phones who I want to support. I think that if QR codes are to be used they have to be usable by at least the first three rows of the audience for a small audience of maybe 50 people as that would allow everyone who’s interested to quickly get in range and scan the code at the end.

Chris Samuel has a photo (taken at the same meeting) showing how a QR code from a phone could be distributed to a room [2]. But that won’t work for all rooms.

One option is to just have the QR code on my phone and allow audience members to scan it after the lecture. As most members of the audience won’t want the URLs it should be possible for the interested people to queue up to scan the QR code(s).

Another possibility I’m considering is to use a temporary post on my documents blog (which isn’t syndicated) for URLs. The WordPress client for Android works reasonably well so I could edit the URL list at any time. That would work reasonably well for talks that have lots of URLs – which is quite rare for me.

A final option is to use Twitter, at the end of a talk I could just tweet the URLs with suitable descriptions. A good portion of the Tweets that I have written is URLs for web sites that I find interesting so this isn’t a change. This is probably the easiest option, but with the usual caveat of using a proprietary service as an interim measure until I get a free software alternative working.

Any suggestions?

Please comment if you have any ideas about ways of addressing these issues.

Also please let me know if anyone is working on a distributed Twitter replacement. Please note that anything which doesn’t support followers on multiple servers and re-tweets and tweeting to users on other servers isn’t useful in this regard.

Replacement Credit Cards and Bank Failings

I just read an interesting article by Brian Krebs about the difficulty in replacing credit cards [1].

The main reason that credit cards need to be replaced is that they have a single set of numbers that is used for all transactions. If credit cards were designed properly for modern use (IE since 2000 or so) they would act as a smart-card as the recommended way of payment in store. Currently I have a Mastercard and an Amex card, the Mastercard (issued about a year ago) has no smart-card feature and as Amex is rejected by most stores I’ve never had a chance to use the smart-card part of a credit card. If all American credit cards had a smart card feature which was recommended by store staff then the problems that Brian documents would never have happened, the attacks on Target and other companies would have got very few card numbers and the companies that make cards wouldn’t have a backlog of orders.

If a bank was to buy USB smart-card readers for all their customers then they would be very cheap (the hardware is simple and therefore the unit price would be low if purchasing a few million). As banks are greedy they could make customers pay for the readers and even make a profit on them. Then for online banking at home the user could use a code that’s generated for the transaction in question and thus avoid most forms of online banking fraud – the only possible form of fraud would be to make a $10 payment to a legitimate company become a $1000 payment to a fraudster but that’s a lot more work and a lot less money than other forms of credit card fraud.

A significant portion of all credit card transactions performed over the phone are made from the customer’s home. Of the ones that aren’t made from home a significant portion would be done from a hotel, office, or other place where a smart-card reader might be conveniently used to generate a one-time code for the transaction.

The main remaining problem seems to be the use of raised numbers. Many years ago it used to be common for credit card purchases to involve using some form of “carbon paper” and the raised numbers made an impression on the credit card transfer form. I don’t recall ever using a credit card in that way, I’ve only had credit cards for about 18 years and my memories of the raised numbers on credit cards being used to make an impression on paper only involve watching my parents pay when I was young. It seems likely that someone who likes paying by credit card and does so at small companies might have some recent experience of “carbon paper” payment, but anyone who prefers EFTPOS and cash probably wouldn’t.

If the credit card number (used for phone and Internet transactions in situations where a smart card reader isn’t available) wasn’t raised then it could be changed by posting a sticker with a new number that the customer could apply to their card. The customer wouldn’t even need to wait for the post before their card could be used again as the smart card part would never be invalid. The magnetic stripe on the card could be changed at any bank and there’s no reason why an ATM couldn’t identify a card by it’s smart-card and then write a new magnetic stripe automatically.

These problems aren’t difficult to solve. The amounts of effort and money involved in solving them are tiny compared to the costs of cleaning up the mess from a major breach such as the recent Target one, the main thing that needs to be done to implement my ideas is widespread support of smart-card readers and that seems to have been done already. It seems to me that the main problem is the incompetence of financial institutions. I think the fact that there’s no serious competitor to Paypal is one of the many obvious proofs of the incompetence of financial companies.

The effective operation of banks is essential to the economy and the savings of individuals are guaranteed by the government (so when a bank fails a lot of tax money will be used). It seems to me that we need to have national banks run by governments with the aim of financial security. Even if banks were good at their business (and they obviously aren’t) I don’t think that they can be trusted with it, an organisation that’s “too big to fail” is too big to lack accountability to the citizens.

Finding Corrupt Files that cause a Kernel Error

There is a BTRFS bug in kernel 3.13 which is triggered by Kmail and causes Kmail index files to become seriously corrupt. Another bug in BTRFS causes a kernel GPF when an application tries to read such a file, that results in a SEGV being sent to the application. After that the kernel ceases to operate correctly for any files on that filesystem and no command other than “reboot -nf” (hard reset without flushing write-back caches) can be relied on to work correctly. The second bug should be fixed in Linux 3.14, I’m not sure about the first one.

In the mean time I have several systems running Kmail on BTRFS which have this problem.

(strace tar cf – . |cat > /dev/null) 2>&1|tail

To discover which file is corrupt I run the above command after a reboot. Below is a sample of the typical output of that command which shows that the file named “.trash.index” is corrupt. After discovering the file name I run “reboot -nf” and then delete the file (the file can be deleted on a clean system but not after a kernel GPF). Of recent times I’ve been doing this about once every 5 days, so on average each Kmail/BTRFS system has been getting disk corruption every two weeks. Fortunately every time the corruption has been on an index file so I don’t need to restore from backups.

newfstatat(4, ".trash.index", {st_mode=S_IFREG|0600, st_size=33, …}, AT_SYMLINK_NOFOLLOW) = 0
openat(4, ".trash.index", O_RDONLY|O_NOCTTY|O_NONBLOCK|O_NOFOLLOW|O_CLOEXEC) = 5
fstat(5, {st_mode=S_IFREG|0600, st_size=33, …}) = 0
read(5,  <unfinished …>
+++ killed by SIGSEGV +++

Comparing Telcos Again

Late last year I compared the prices of mobile providers after Aldi started getting greedy [1]. Now Aldi have dramatically changed their offerings [2] so at least some of the phones I manage have to be switched to another provider.

There are three types of use that are of interest to me. One is for significant use, that means hours of calls per month, lots of SMS, and at least 2G of data transfer. Another is for very light use, maybe a few minutes of calls per month where the aim is to have the lowest annual price for an almost unused phone. The third is somewhere in between – and being able to easily switch between plans for moderate and significant use is a major benefit.

Firstly please note that I have no plans to try and compare all telcos, I’ll only compare ones that seem to have good offers. Ones with excessive penalty clauses or other potential traps are excluded.

Sensible Plans

The following table has the minimum costs for plans where the amount paid counts as credit for calls and data, this makes it easy to compare those plans.

Plan Cost per min or SMS Data Minimum cost
AmaySIM As You Go [3] $0.12 $0.05/meg, $19.90 for 2.5G in 30 days, $99.90 for 10G in 365days $10 per 90 days
AmaySIM Flexi [4] $0.09 500M included, free calls to other AmaySIM users, $19.90 for 2.5G in 30 days, $99.90 for 10G in 365days $19.90 per 30 days
Aldi pre-paid [5] $0.12 $0.05/meg, $30 for 3G in 30 days $15 per 365 days

Amaysim has a $39.90 “Unlimited” plan which doesn’t have any specific limits on the number of calls and SMS (unlike Aldi “Unlimited”) [6], that plan also offers 4G of data per month. The only down-side is that changing between plans is difficult enough to discourage people from doing so, but if you use your phone a lot every month then this would be OK. AmaySIM uses the Optus network.

Lebara has a $29.90 “National Unlimited” plan that offers unlimited calls and SMS and 2G of data [7]. The Lebara web site doesn’t seem to include details such as how long pre-paid credit lasts, the lack of such detail doesn’t give me confidence in their service. Lebara uses the Vodafone network which used to have significant problems, hopefully they fixed it. My lack of confidence in the Vodafone network and in Lebara’s operations makes me inclined to avoid them.

Obscure Plans

Telechoice has a $28 per month “i28″ plan that offers unlimited SMS, $650 of calls (which can be international) at a rate of over $1 per minute, unlimited SMS, unlimited calls to other Telechoice customers, and 2G of data [8]. According to the Whirlpool forum they use the Telstra network although the TeleChoice web site doesn’t state this (one of many failings of a horrible site).

The TeleChoice Global Liberty Starter plan costs $20 per month and includes unlimited calls to other TeleChoice customers, unlimited SMS, $500 of calls at a rate of over $1 per minute, and 1G of data [9].

Which One to Choose

For my relatives who only rarely use their phones the best options are the AmaySIM “As You Go” [3] plan which costs $40 per 360 days and the Aldi prepaid which costs $15 per year. Those relatives are already on Aldi and it seems that the best option for them is to keep using it.

My wife typically uses slightly less than 1G of data per month and makes about 25 minutes of calls and SMS. For her use the best option is the AmaySIM “As You Go” [3] plan which will cost her about $4 in calls per month and $99.90 for 10G of data which will last 10 months. That will average out to about $13 per month. It could end up being a bit less because the 10G of data that can be used in a year gives an incentive to reduce data use while previously with Aldi she had no reason to use less than 2G of data per month. Her average cost will be $11.30 per month if she can make 10G of data last a year. The TeleChoice “Global Liberty Starter” [9] plan is also appealing, but it is a little more expensive at $20 per month, it would be good value for someone who averages more than 83 minutes per month and also uses almost 1G of data.

Some of my relatives use significantly less than 1G of data per month. For someone who uses less than 166MB of billable data per month then the Aldi pre-paid rate of $0.05 per meg [5] is the best, but with a modern phone that does so many things in the background and a plan that rounds up data use it seems almost impossible to be billed for less than 300MB/month. Even when you tell the phone not to use any mobile data some phones still do, on a Nexus 4 and a Nexus 5 I’ve found that the only way to prevent being billed for 3G data transfer is to delete the APN from the phone’s configuration. So it seems that the AmaySIM “As You Go” [3] plan with a 10G annual data pack is the best option.

One of my relatives needs less than 1G of data per month and not many calls, but needs to be on the Telstra network because their holiday home is out of range of Optus. For them the TeleChoice Global Liberty Starter [9] plan seems best.

I have been averaging a bit less than 2G of data transfer per month. If I use the AmaySIM “As You Go” [3] plan with the 10G data packs then I would probably average about $18 worth of data per month. If I could keep my average number of phone calls below $10 (83 minutes) then that would be the cheapest option. However I sometimes spend longer than that on the phone (one client with a difficult problem can involve an hour on the phone). So the TeleChoice i28 plan looks like the best option for me, it gives $650 of calls at a rate of $0.97 per minute + $0.40 connection (that’s $58.60 for a hour long call – I can do 11 of those calls in a month) and 2G of data. The Telstra coverage is an advantage for TeleChoice, I can run my phone as a Wifi access point so my wife can use the Internet when we are out of Optus range.

Please let me know if there are any good Australian telcos you think I’ve missed or if there are any problems with the above telcos that I’m not aware of.

Links March 2014

Typing Animal wrote an interesting article about the dangers of stainless steel in a medical environment [1]. Apparently silver and copper are best due to the oligodynamic effect. Instead of stainless steel drinking bottles they should sell silver plated drinking bottles for kids, I’m sure that lots of parents would pay extra for that.

Mark Kendall gave an interesting TED talk about a replacement for the hypodermic syringe in vaccinations [2]. His invention can reduce the cost of immunisation while increasing the effectiveness and avoiding problems with people who have a needle phobia.

The TED blog has an interesting interview with Will Potter about the use of the “war on terror” to silence journalists and the invention of the term “eco terrorism” for non-violent people who are politically active [3].

The TED blog has an interesting article by Kate Torgovnick May about designing products for sustainability [4]. It links to an insightful TED talk by Leyla Acaroglu about some of the complex issues related to sustainability [5].

Manoush Zomorodi wrote an informative article about How one college went from 10% female computer-science majors to 40% [6].

Slate has an interesting article by Jamelle Bouie showing the way that support for capital punishment in the US is linked to racism [7].

The Southern California Public Radio blog has an interesting article by Josie Huang about Suey Park and her success in using twitter to oppose racism [8].

Andrew Solomon wrote an insightful interview with the father of Adam Lanza for the New Yorker [9].

Waleed Aly wrote an insightful article about George Brandis’ attempt to change the Racial Discrimination Act specifically to allow Andrew Bolt to be racist [10]. He describes it as “the whitest piece of proposed legislation I’ve encountered” which is significant in a country with as much racism as Australia. Really we need stronger laws against racism, there should be no right to be bigoted.

A German Court has ruled that “non commercial” licenses don’t permit non-commercial organisations to re-publish material [11]. This seems bogus to me, I’d be happy to have my non-commercial licensed work published by a non-commercial publishing organisation – just as long as they don’t run adverts on the page.

Professors Woolley and Malone wrote an interesting article about their research into group performance, apparently having more women in a group improves the collective intelligence of a group, but having smarter men in the group doesn’t [12].

Susie Hill wrote an article about the SPARX computer game that is designed to treat adolescent depression [13]. They are working on a “rainbow” edition for GLBT kids and a version for Maoris. Unfortunately their web site is down right now and the version at archive.org says that it’s currently only available to participants in a clinical trial.

Tim Chevalier wrote an insightful article explaining why people who campaign against equality shouldn’t be given senior positions in corporations [14].

Zeynep Tufekci wrote an insightful article about how French High Theory and Dr. Seuss can help explain gender problems in geek communities [15].

Hannah Levintova wrote an informative article for Mother Jones about how the US based hate group the World Congress of Families incites homophobic violence in Russia [16].

Josh Sanburn wrote an article for Time about people in the Deep South who claim to be Christian giving away guns to encourage people to attend church [17]. This is the same part of the world where people who claimed to be Christian used their “religion” as an excuse for supporting slavery. I’m quitting bourbon, too much evil comes from that part of the world and I’m not buying anything that comes from there.