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This morning while travelling to work by tram I had another visual migraine. It was a little worse than last time, not only did everything I focussed on appear to shimmer, but things went a bit grey at my peripheral vision. I had a headache as well although it was very mild (not the typical migraine headache).
It was convenient that the vision problems almost exactly matched the time of my tram journey so that it didn’t cause me to waste much time. One visual migraine every three months is something that won’t inconvenience me much. I just hope that I don’t get other migraine symptoms in future.
I’m in the process of converting my Fedora/rawhide laptop to Debian.
On Fedora the AES encrypted filesystems deliver about 38MB/s read speed according to dd. On Debian the speed is 2.4MB/s when running Xen and 2.7MB/s when not running Xen. The tests were done on the same block device.
Debian uses a SMP kernel (there are no non-SMP kernels in Debian), but I don’t expect this to give an order of magnitude performance drop. Both systems use i686 optimised kernels.
Update: As suggested I replaced the aes module with the aes_586 module. Unfortunately it made no apparent difference.
Update2: As suggested by a comment I checked the drive settings with hdparm and discovered that my hard drive was not using DMA. After I configured the initramfs to load the piix driver first it all started working correctly. Thanks for all the suggestions, I’ll post some benchmarks of encryption performance in a future blog entry.
The Lexus GS 450 hybrid petrol/electric car has been given the award for Australia’s best luxury car!
The judging for this contest rated fuel efficiency as low importance, because luxury car owners traditionally aren’t very concerned about such things. The Lexus won because of it’s quiet engine (can’t beat an electric motor at low speed), high performance (3.5L petrol engine that outperforms mode 4L engines because of the electric motor assistance), safety, security, and other factors.
There has been an idea that hybrid cars are only for people who want to protect the environment at all costs. The result of this contest proves that idea to be false. The Lexus won by simply being a better luxury car, the features that benefit the environment also give a smoother and quieter ride and higher performance – which are factors that are very important to that market segment! Also it wasn’t even a close contest, the nearest rival achieved an aggregate score of 9% less (a significant difference as there was a mere 2.5% difference in score between the 2nd place and 5th place).
This of course shouldn’t be any surprise. The high torque that electric motors can provide at low speed is well known – it’s the reason for Diesel-electric hybrid power systems in locomotives. It was only a matter of time before similar technology was introduced for cars for exactly the same reasons. The next development will be hybrid Diesel-electric trucks.
/tmp /mnt/bind bind bind 0 0
Today I discovered that the above syntax works in the /etc/fstab file. This enables a bind mount of /tmp to /mnt/bind which effectively makes /mnt/bind a hard link to /tmp. The same result can be achieved by the following command, but last time I tried (quite some time ago) it didn’t seem to work in /etc/fstab – but now it works in both SUSE and Debian.
mount –bind /tmp /mnt/bind
Also I recently discovered that 0.0.0.0 is an alias to 127.0.0.1. So for almost any command that takes an IP address you can use either address with equal results (apart from commands which interpret the string and consider 0.0.0.0 to be invalid). I can’t think of any benefit to using this, and challenge the readers to post a comment (or make their own blog post if they so wish) demonstrating it’s utility.
This morning I received an email from the AMD Developer Center advising me that I need to fill out their NDA if I want access to their development machines.
I have a vague recollection that when AMD64 was first released I was very keep to get access to such hardware and had applied to AMD for access to their machines.
Of course now the second-hand market is full of AMD64 machines and I’ve got one in my server room so it’s not as useful as it once was. I don’t even know why AMD would still run a developer center given that everyone who wants AMD64 machines can cheaply buy as many as they want and organizations such as Sourceforge and Debian provide access to such machines for their members.
While I appreciate what AMD is doing, it probably would be best if companies could adopt a standard timeout for electronic correspondence. If someone doesn’t follow up for X months then you should assume that they are not interested.
Are comment-less blogs missing the spirit of blogging?
It seems to me that the most significant development about blogging is the idea that anyone can write. Prior to blogs news-papers were the only method of writing topical articles for a mass audience. To be able to write for a news-paper you had to be employed there or get a guest writing spot (not sure how you achieve this but examples are common).
Anyone can start a blog, if there is a community that you are part of which has a planet then it’s not difficult to get your blog syndicated and have some reasonable readership. Even the most popular planets have less readers than most small papers, but that combined with the ease of forwarding articles gives a decent readership.
It seems to me that the major characteristic that separates a blog from an online newspaper is the low entry requirements, anyone can create one.
Every news-paper that is remotely worth reading has a letters column to publish feedback from readers. Of course it’s heavily moderated and getting even 50% of your letters published is something to be proud of. But it does create a limited forum to discuss the articles that are published.
It seems to me that creating a blog and denying the readers the ability to comment on it is in some ways making the blog less open than a news-paper column. When such blogs are aggregated in a community planet feed it seems that they go against the community spirit. It also drives people to make one-line blog posts in response, which I regard as a bad thing.
The comments on my blog are generally of a high quality, I’ve had a few anonymous flame comments – but you have to learn to deal with a few flames if you are going to use the net, and people who are afraid to publish their real name to a flame don’t deserve much attention. I’ve had one comment which might have been an attempt to advertise a product (so I deleted it just to be safe). But apart from that the comments are generally very good. I’ve learned quite a few useful things from blog comments, sometimes I mention having technical problems in blog posts and blog comments provide the solution. Other times they suggest topics for further writing.
There are facilities for moderated blog comments that some people use. If you have a really popular blog then it’s probably a good idea to moderate the comments to avoid spam, but I’m not that popular yet and most people who blog will never be so popular. At this time blog moderation would be more trouble for me than it’s worth.
In conclusion I believe that the web should be about interactive communication in all areas, it should provide a level playing field where the participation of all individuals is limited only by time and ability. Refusing comments on blogs is a small step away from that goal.
At OSDC Mary Gardiner gave a talk titled The Planet Feed Reader: Better Living Through Gravity. During the course of the presentation she expressed the opinion that short dialog based blog entries are a sign of a well running planet.
Certainly if blog posts respond to each other then there is a community interaction, and if that is what you desire from a planet then it can be considered a good thing. Mary seemed focussed on planets for internal use rather than for people outside the community which makes the interaction more important.
However I believe that planets are not a direct substitute for mailing lists. On a mailing list you can reply to a message agreeing with it and expect that the same people who saw the original message will see your reply. Blogs however are each syndicated separately so a blog post in response to someone else’s blog should be readable on it’s own. A one line post saying “John is right” provides little value to people who don’t know who John is, especially if you don’t provide a link to John’s post that you agree with.
On Planet Debian there have been a few contentious issues discussed where multiple people posted one-line blog entries. I believe that the effective way to communicate their opinions would either be to write a short essay (maybe 2-3 paragraphs) explaining their opinion and the reasons for it, or if they have no new insight to contribute then they should summarise the discussion.
I believe that a planet such as Planet Debian or Planet Linux Australia should not only be a forum for people who are in the community but also an introduction to the community for people who are outside. AOL posts don’t help in this regard.
One final thing to note is that blogs already do have a feature for allowing “me too” responses, it’s the blog comment facility…
PS Above is a picture of day 59 of the beard, it was taken on the 5th of December (I’ve been a little slack with beard pictures).
On several occasions in discussions about life etc friends have mentioned the theory that quantum mechanics dictates the way our cells work. In the past I have not been convinced. However this site http://www.surrey.ac.uk/qe/Outline.htm has a very well written description of the theory which is very compelling.
On a mailing list some questions were asked about disk encryption, I decided to blog the answer for the benefit of others:
What type of encryption would be the strongest? the uncrackable if you will? im not interested in DES as this is a US govt recommendation – IDEA seems good but what kernel module implements this?
The US government (which incidentally employs some of the best cryptologists in the world) recommends encryption methods for data that is important to US interests (US military and banking operations for starters). Why wouldn’t you want to follow those recommendations? Do you think that they are putting back-doors in their own systems?
If they were putting in back-doors do you think that they would use them (and potentially reveal their methods) for something as unimportant as your data?
I think that if the US military wanted to apply a serious effort to breaking the encryption on your data then you would have an assortment of other things to worry about, most of which would be more important to you than the integrity of your data.
I’ve read some good things about keeping a usb key for system boot so that anything on the computer itself is unreadable without the key – but thats simply just a physical object – I’d like both the system to ask for the passphrase for the key as well as needing the usb key
I believe that can be done with LUKS, however it seemed broken last time I experimented with it so I’ve stuck with the older operation of cryptsetup.
What kind of overheads does something like this entangle? – will my system crawl because of the constant IO load of the disk?
My laptop has a Pentium-M 1.7GHz and a typical laptop drive. The ratio of CPU power to hard drive speed is reasonable. For most operations I don’t notice the overhead of encryption, the only problem is when performing CPU intensive IO operations (such as bzip compression of large files). When an application and the kernel both want to use a lot of CPU time then things can get slow.
More recent machines have a much higher ratio of CPU power to disk IO as CPU technology has been advancing much faster than disk technology. A high-end desktop system might have 2-3x the IO capacity
of my machine, but a single core would have 2-3x the computer power of the CPU in my laptop and for any system you might desire nowadays 2 cores is the minimum. Single-core machines are still on sale and still work well for many people – I am still deploying Pentium-3 machines in new installations, but for machines that make people drool it’s all dual-core in laptops and one or two dual-core CPUs in desktop systems (with quad core CPUs on sale soon).
If you want to encrypt data on a P3 system with a RAID array (EG a P3 server) then you should expect some performance loss. But for a typical modern desktop system you shouldn’t expect to notice any overhead.
I just lent two 80G IDE drives to a friend, and he re-paid me with 160G drives. Generally I don’t mind people repaying hardware loans with better gear (much better than repaying with the same gear after a long delay and depreciation), but this concerns me.
My friend gave me the 160G drives because he can’t purchase new 80G drives any more, his supplier has nothing smaller than 160G. I have some very reliable machines that I don’t want to discard which won’t support 160G drives – I’m not even sure that they would boot with them! Now I’m going to have to stock-pile 40G disks.
The machines I am most concerned about are my Cobalt machines. They are nice little servers that are quiet and use only 20W of electricity!
It’s a pity that there aren’t any cheap flash storage devices that connect to an IDE bus. If I could get my Cobalt machines running with flash storage they would be even more quiet and energy efficient while not being at risk of mechanical damage, and I doubt that flash storage will exceed 40G of capacity for a while.
Update: I’ve set a new personal record for rapid comments on a blog entry, all telling me that it is possible to get CF to IDE adapters. Thanks for the information, I appreciate it and will consider it for some machines. The problem however is that the price of a CF to IDE adapter plus the cost of a CF card of suitable size is moderately high (more than the cheaper hard drives), while CF capacity generally is only just usable for a mainstream Linux distribution.
These factors combine to make CF-IDE devices an option for only certain corner cases, not really an option to replace all the hard drives in machines that matter to me. I will probably use it for at least one of my Cobalt machines though.
Update2: Julien just informed me of the new Samsung flash-based laptop drives that will have capacities up to 16G (or 32G according to other web sites). I’m now trying to discover where to buy them.
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