Will installing Ubuntu onto a Btrfs partition be an option in Karmic? With "Btrfs -o compression" I can fit a full development environment, and build GUI applications like LyX in just 1.4GB of space [1]. This means that 2GB-4GB SSD devices are big enough for real world uses.
I doubt that btrfs will be stable in time for Karmic [2]. However I don't store irreplaceable data on such devices anyway, so if it is easy to reinstall Ubuntu onto btrfs the cost of dataloss is very low for users such as myself. Additionally, if btrfs is availiable in an unofficial unsupported and perhaps hidden way in Karmic, I imagine there would be less surprises if official support is added in Ubuntu 10.04. [1] This is 2.7GB of data. Unlike btrfs and reiserfs, ext3 lacks support for space efficient storage of small files, so this takes 3.2GB of space. As shown below btrfs takes just 1.4GB to stor this [2] Btrfs is in mainline, and btrfs is expected to be backwards compatible from now on. Filesystem Size Used Avail Use% Mounted on /dev/sda1 12G 3.2G 7.6G 30% / /dev/sdc1 4.0G 1.4G 2.7G 34% /home/xp/btfs I did some back of the envelope benchmarks of the compression feature (not on SSD though). These compare the time taken to read/write the entire 2.7GB. The btrfs -o compress partition came in slightly faster for cold. It took only 37sec compared to 41sec for ext3. This is despite the fact that: clearly part of the real ext3 partition was cached, btrfs does not support LZO compression yet, and I was using the old 0.17 module rather than the faster 0.19 one. Interestingly, reading the compressed filesystem did not seemed to use less than 50% of the CPU of the VM. As we might expected the warm reads were faster for ext3 than btrfs -o compress, at 22 seconds instead of 9 seconds. Since these figures are very back-of- the envelope I wouldn't trust them much, but this does suggest that btrfs -o compress will hold its own for read io bound tasks, presumably including booting from a slow external SSD. The figures below are at least testing a possible real world use, unlike the benchmarks which are just reading and writing zeros. Cold reads. time sudo tar --one-file-system -c / > /dev/null real 0m41.073s user 0m0.632s sys 0m9.585s time sudo tar --one-file-system -c /home/xp/btfs/ > /dev/null real 0m37.861s user 0m0.704s sys 0m17.033s Warm reads (cached). time sudo tar --one-file-system -c / > /dev/null real 0m9.751s user 0m0.160s sys 0m7.368s time sudo tar --one-file-system -c /home/xp/btfs/ > /dev/null real 0m22.725s user 0m0.588s sys 0m16.609s In the future, it may even be possible to also use btrfs in place of squashfs. In which case "installing" to a USB-disk could as simple as booting the netbook remix image on the USB disk, and using btrfs's online resize feature to use the full size of the SDD.
