Holy Cow – BTRFS!

Recently I have been experimenting with BTRFS. BTRFS is a relatively new filesystem which has modern features, high performance, scalability, supporting file-system snapshots and on-the-fly compression.

After spending the week running BTRFS on Ubuntu from within a Virtualbox VM I reinstalled my laptop using it. Ubuntu’s installer supports creating btrfs partitions, which is handy, and it is reported to work even as a boot partition. I had problems using BTRFS as the boot partition however, so elected to use ext2 for boot in the real install.

The installer doesn’t support enabling the on the fly compression, so once I had the system installed I edited /etc/fstab adding “compress=lzo”, I added “ssd” as I have an SSD and “space_cache” which is reported to improve performance. After I rebooted I ran a filesystem balance to compress any existing compressible data like so:-

btrfs fi balance /
btrfs fi balance /home

It’s worth pointing out here that there still isn’t a utility which can fix BTRFS filesystem corruption, so although BTRFS is considered stable, you may want to stay away from it just in case. There is also a nasty condition that can cause a kernel crash if the file-system runs out of space, so that is another one to watch for.

Continue reading Holy Cow – BTRFS!

Partition alignment largely a moot point now

To summarise. It is very important for recent disk performance that partitions are aligned on a 1MB/2048 sector boundary. This stops data from sitting astride blocks and killing disk performance. It is especially important with first generation SSDs, as they have poor write performance anyway, and will save your SSD from an early demise (flash memory has limited write cycles).

Windows Vista and above will use the 2048 sector alignment as will Ubuntu, so it isn’t necessary to worry about this issue any more, unless you are installing Windows XP. MAC OS X is the big loser in all of this as it doesn’t care about alignment beyond 4k which may or may not work well depending on the specific block size of your HD/SSD.

Continue reading Partition alignment largely a moot point now