Btrfs as default filesystem for Fedora 23?

[Josh Boyer]

On Tue, Jun 23, 2015 at 9:07 PM, Stephen John Smoogen <smooge at gmail.com> wrote:
> On 23 June 2015 at 18:40, Neal Gompa <ngompa13 at gmail.com> wrote:
>> That is precisely why I'm asking on this list. I don't know who those people
>> are, and this is really the best place I know of to start contact and those
>> discussions.
>>
>>
>
> My apologies.. my tone was not helpful. You are correct that asking
> here is where to start. I think the groups who would be able to help
> answer would be
>
> 1. Kernel team

The Fedora kernel team is fairly tired of having this same
conversation every release[1].  Progress is certainly being made
upstream and it is encouraging to see issues get fixed.  However, most
of the same points we brought up last time this was discussed still
exist.  So in the interest of being clear, our official position is
that we would not recommend btrfs as the default filesystem in any
Fedora Edition.  Here are a few reasons why.

1) The upstream maintainers (primarily Josef) have repeatedly said
[2][3] btrfs is not ready to be default and that they would advocate
for a change when btrfs is ready.  That has not happened.

2) The Fedora kernel team does not have extensive knowledge or
expertise available to debug btrfs issues.  While this is generally
true for a lot of the kernel subsystems, we do have expertise
available to us for ext4 and XFS.  We tend to value user data very
highly, and having additional filesystem developers readily available
to help fix issues found in Fedora is extremely important to us.

3) The level of effort around btrfs in Fedora outside of our team is
fairly limited.  We have a few people plugging away at testing and
reporting upstream, which is excellent to see and should be encourage.
Some may suggest this is a chicken and egg situation, but btrfs has
been available as a general filesystem choice on install since F16.
None of the features people seem to want from btrfs have been further
integrated into the distro at all.  Things like backup/restore via
snapshot, update/rollback via snapshot, etc have no distro level
integration at all.  The btrfs-progs and Snapper packages are in the
repository, but that is about it.

4) As mentioned before, the filesystem is general available for those
that wish to use it.  It is an installation choice in the installer.
Considering some of the above points, it is not immediately clear why
btrfs would need to be the default at all.  Assuming the above 3
points improve, we don't foresee Server switching away from XFS
anytime soon.  Cloud/Atomic get no major benefits from using it
(CoreOS recently moved away from btrfs).  Workstation is the most
likely target but even there it is unclear how much of a benefit it
would bring.

With all that being said, the choice of filesystem is ultimately up to
the Working Groups and end users.  Our input is just one piece of the
puzzle.  We likely don't have much else to say on this topic, but
please keep the above points in mind in your further discussions.

josh (for the Fedora kernel team)

[1]https://lists.fedoraproject.org/pipermail/desktop/2014-March/009411.html
[2]https://lists.fedoraproject.org/pipermail/devel/2014-February/196006.html
(F21)
[3]https://lists.fedoraproject.org/pipermail/devel/2014-October/203058.html
(F22)