Just one comment on the standby-replay setting: it really depends on
the use-case, it can make things worse during failover. Just recently
we had a customer where disabling standby-replay made failovers even
faster and cleaner in a heavily used cluster. With standby-replay they
had to manually clean things up in the mounted directory. So I would
recommend to test both options.
Zitat von William Edwards <wedwa...@cyberfusion.nl>:
Op 26 okt. 2022 om 10:11 heeft mj <li...@merit.unu.edu> het
volgende geschreven:
Hi!
We have read https://docs.ceph.com/en/latest/man/8/mount.ceph, and
would like to see our expectations confirmed (or denied) here. :-)
Suppose we build a three-node cluster, three monitors, three MDSs,
etc, in order to export a cephfs to multiple client nodes.
On the (RHEL8) clients (web application servers) fstab, we will
mount the cephfs like:
cehp1,ceph2,ceph3:/ /mnt/ha-pool/ ceph
name=admin,secretfile=/etc/ceph/admin.secret,noatime 0 2
We expect that the RHEL clients will then be able to use
(read/write) a shared /mnt/ha-pool directory simultaneously.
Our question: how HA can we expect this setup to be? Looking for
some practical experience here.
Specific: Can we reboot any of the three involved ceph servers
without the clients noticing anything? Or will there be certain
timeouts involved, during which /mnt/ha-pool/ will appear
unresposive, and *after* a timeout the client switches monitor
node, and /mnt/ha-pool/ will respond again?
Monitor failovers don’t cause a noticeable disruption IIRC.
MDS failovers do. The MDS needs to replay. You can minimise the
effect with mds_standby_replay.
Of course we hope the answer is: in such a setup, cephfs clients
should not notice a reboot at all. :-)
All the best!
MJ
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