https://lkml.org/lkml/2010/6/3/313 explains that btrfs has unbounded internal fragmentation. The author of the article you linked criticized ZFS' external fragmentation, but completely ignored the unbound internal fragmentation of btrfs. ZFS has ARC, which compensates for ZFS' external fragmentation. ARC also enables ZFS to outperform many other filesystems. btrfs simply becomes slower until either it runs out of space or is manually rebalanced. The manual rebalancing process kills IO performance while it runs. I am told that it is especially crippling on pre-SATA 3.1 SSDs when mounted with discard. To illustrate what I mean when I say btrfs can run out of space due to its unbound internal fragmentation, imagine a 256GB SSD formatted with btrfs that becomes full after only 25 gigabytes have been written.
Originally Posted by RahulSundaram
As for having "conservative distros" use btrfs, I think people are more concerned about what the default filesystem is than they are about support for the filesystem. I am not aware of any major Linux distributions that use btrfs as their default filesystem.
Last edited by ryao; 01-17-2013 at 04:02 PM.