[elrepo] BTRFS for RHEL 8

[Konstantin Olchanski]

On Tue, Jan 21, 2020 at 09:13:33PM +0000, Joseph Christopher Sible wrote:
> Red Hat removed all traces of BTRFS from RHEL 8. However, I did some searching online and found
> evidence that ELRepo has packages that bring it back. https://unix.stackexchange.com/a/545089 and
> https://centosfaq.org/centos/missing-packages-in-centos8-mirrors-or-do-i-miss-something/#comment-128436
> both seem to say that kmod-btrfs and btrfs-progs are available in ELRepo 8 Testing. However, I don't
> see them there. What am I missing? Where are they?

FWIW, a few years ago I evaluated btrfs as shipped in centos-7.1 (or 7.2 or 7.3)
for replacement of mdadm raid6+xfs for small storage arrays (up to 8 disks).

In my evaluation, many btrfs things worked very well (better than zfs), but
I immediately ran into a number of problems that are show stoppers and
(the best I can tell) are still not fixed:

- failure of one disk resulted in filling the syslog with an infinite
  stream of errors (vs mdadm raid and zfs faulting-out the bad disk)
- systemd refused to boot in the presence of a degraded btrfs filesystem
- raid5/raid6 are still labeled "unstable, write hole exists", fix proposed
  in 2017 (today is 2020), see https://btrfs.wiki.kernel.org/index.php/RAID56

Since then, I switched from mdadm+xfs to ZFS (mirrored home directories and
raid6 data arrays). It works well enough.

When btrfs has stable raid5/raid6 I will look at it again.

I would think Red Hat did a similar evaluation with similar results
leading to their decision to remove btrfs completely.

P.S

If the OP succeeds in installing btrfs, I would like to hear from them
about the latest status of booting in the presence of degraded btrfs
filesystems (i.e. one disk missing from mirror or raid5/raid6). Last time
I tried, booting stalled in systemd waiting for the missing (failed) disk
to come online. All suggested workarounds (about 3 or 4 of them) did not work.

-- 
Konstantin Olchanski
Data Acquisition Systems: The Bytes Must Flow!
Email: olchansk-at-triumf-dot-ca
Snail mail: 4004 Wesbrook Mall, TRIUMF, Vancouver, B.C., V6T 2A3, Canada