On 2017-08-02 08:55, Lutz Vieweg wrote:
On 08/02/2017 01:25 PM, Austin S. Hemmelgarn wrote:
And this is a worst-case result of the fact that most
distros added BTRFS support long before it was ready.
RedHat still advertises "Ceph", and given Ceph initially recommended
btrfs as
the filesystem to use for its nodes, it is interesting to read how clearly
they recommend against btrfs now:
http://docs.ceph.com/docs/master/rados/configuration/filesystem-recommendations/
We recommand against using btrfs due to the lack of a stable version
to test against and frequent bugs in the ENOSPC handling.
Yes, and the one thing they don't mention there is that Ceph is already
doing most of the same things that BTRFS is, so you end up having
performance issues due to duplicated work too. What they specifically
call out though is first the reason that it should not be supported yet
in RHEL, OEL, and many other distros (I'm explicitly leaving
SLES/OpenSUSE off of that list, because while I disagree with their
choices of default behavior WRT BTRFS, they are actively involved in
it's development, unlike most of the other distros that 'support' it),
and then second one of the biggest issues for regular usage.
German IT magazine "Golem" speculates that RedHat's decision
is influenced by its recent acquisition of Permabit.
But I don't really see how XFS or Permabit tackle the problem
that if you need to create consistent backups of file systems while they
are
in use, block-device level snapshots damage the write performance
big time.
When you're talking about data safety though, most people are willing to
sacrifice write performance in favor of significantly lowering perceived
risk. The misguided early support of BTRFS without sufficient
explanation of exactly how 'in-development' it is by many distros means
that there are a lot of stories of issues and failures with BTRFS than
ones of success (partly also because the filesystem is one of those
things that people tend to complain about if it breaks, and not praise
all that much if it works), and as a result, the general perception
outside of people who use it actively is that it's pretty risky to use
(which is absolutely accurate if you don't do routine maintenance on it).
(That backup topic is the one reason we use btrfs for a lot of
/home/ directories.)
I understand that XFS is expected to get some COW-features in the future
as well - but it remains to be seen what performance and robustness
implications that will have on XFS.
I believe basic reflink functionality is already upstream, and I wasn't
aware of any other specific development for XFS.
--
To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
