Btrfs or how to lose space
On the linux-btrfs mailinglist there was an interesting entry about internal fragmentation in btrfs. A basic test brought up many questions about the btrfs filesystem design. Btrfs is a filesystem that uses the b-tree algorithm. There has been a debate if it is a good idea to use b-trees for filesystems. I'm not enough into algorithms, but I let you decide... The test consists of a loop, creating as much 2k sized files as possible on a 1GB Filesystem: # for i in $(seq 1000000); \ do dd if=/dev/zero of=/mnt/file_$i bs=2048 count=1; done (terminated after getting "No space left on device" reports). The result from Edward Shishkin (RedHat) was 59480 Files. This would give us 2048*59480 ~ 116MB. Or in other words, we would waste around 880MB of Space. In the meanwhile, Chris Mason, inventor of btrfs created a patch for increased utilisation. He was able to achieve 106894 Files. That's 208 MB or a waste of 800MB. I'm not sure what he meant by the comm...
