While it originally appeared that Fedora 16
would be the first major distribution (besides possibly counting MeeGo) to switch to Btrfs
as the default Linux file-system, that's not going to happen. Fedora 16 will continue defaulting to EXT4 and it will not be until Fedora 17 now that Btrfs will be the Fedora file-system default.
Josef Back said outright in a mailing list message
, "BTRFS WILL NOT BE THE DEFAULT FILE SYSTEM FOR F16."
This follows many users and developers wondering whether or not Fedora 16 would change to Btrfs from EXT4. The reason for delaying the switch is that the Btrfs engineering requirements haven't been met. In particular, there still isn't a suitable tool for testing and repairing Btrfs file-systems. Such a Btrfs utility is expected soon, but the deadline for having one ready was Fedora 16 Alpha. As a result, Btrfs isn't ready until at least Fedora 17.
is a very nice file-system and has numerous advantages over EXT4 (e.g. SSD optimizations, Gzip/Zlib compression, copy-on-write snapshots, etc), but for now you will need to manually opt to using Btrfs when installing Fedora. In the Ubuntu camp, they will not be moving to Btrfs until at least Ubuntu 12.10 (October 2012), but there too it's currently a non-default install time option.