Linux Magazine take a look into some of the new features/additions/changes in the 2.6.38 kernel.

In addition to the VFS patches, there were a number of file systems improvements in the 2.6.38 kernel.

Btrfs
There were a couple of good additions to btrfs. The first addition was to add LZO compression to btrfs. LZO compression is fairly fast and is built into the kernel so it’s a very logical place for file systems to go for compression capabilities with good performance and good compression.

The second feature added to btrfs is read-only snapshots. As any good storage administrator knows, having the ability to take snapshots but mark them read-only is the first step in a back-up process. You take the read-only snapshot so that it can’t be changed while you’re doing the backup. But, since it’s read-only, the amount of space it takes is fairly low and once the backup is done, it can be easily discarded. This is a very nice addition for btrfs and points to some more mainstream tools making their way into btrfs.

  Storage Highlights in Linux Kernel 2.6.38