BTRFS in 2.6.31-rcwhatever

Josef Bacik josef at toxicpanda.com
Wed Jun 17 16:27:34 UTC 2009


Hello,

It seems there has been some confusion about BTRFS and the new format,
so let me try and clear some things up

1) Btrfs is an experimental and unstable fs that is to be used for
testing only as it could eat your data.
2) Btrfs is an experimental and unstable fs that is to be used for
testing only as it could eat your data.
3) Btrfs is an experimental and unstable fs that is to be used for
testing only as it could eat your data.

Ok now that we have that out of the way,

4) The merge window opened last week for 2.6.31, at which point a new
disk format for btrfs was sucked into the kernel.
5) This new disk format is _incompatible_ with older kernels, which
means that older kernels will not mount a fs with the new format.
Nothing bad will happen if you try to boot into an older kernel, you
won't lose data, it just won't work.
6) This new disk format is automatic.  As soon as you boot into the
new kernel, your filesystem will be automatically converted to the new
format.  There is nothing you can do, so if you don't want the new
format, don't run the new kernel.

At some point in the next few weeks this kernel will land in rawhide.
I will try and make sure btrfs-progs-0.19 goes out at the same time.
The new btrfs-progs isn't essential for running the new format, so if
you just install the kernel you will be fine, but obviously some of
the commands may not work properly.

So if you installed onto btrfs, be careful about going to rawhide,
since you will not be able to go back if you do.

Btrfs will not be as stable as ext4 currently is for at least another
year, so it is still very much just for testing.  I am very interested
in hearing about bugs and getting them fixed, however there will be
little to nothing that I can do if you lose data.  Thank you,

Josef




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