On 13/06/2024 08:54, Janne Johansson wrote:
We made a mistake when we moved the servers physically so while the
replica 3 is intact the crush tree is not accurate.
If we just remedy the situation with "ceph osd crush move ceph-flashX
datacenter=Y" we will just end up with a lot of misplaced data and some
churn, right? Or will the affected pool go degraded/unavailable?
I know I am late here, but for the record, if you ask crush to change
in such a way that PGs are asked to move to "impossible" places, they
will just end up being remapped/misplaced and continue to serve data.
They will obviously not backfill anywhere, but they will also not
cause troubles apart from ceph -s telling you the whole pool(s) is
misplaced currently. Then you can revert the crush change and
everything goes back to normal again.
I have made such "mistakes" several times, and ceph kept going even
though I panicked and flailed with my arms a lot until I managed to
revert the bad crush map changes.
Good to know, thanks =)
Mvh.
Torkil
--
Torkil Svensgaard
Sysadmin
MR-Forskningssektionen, afs. 714
DRCMR, Danish Research Centre for Magnetic Resonance
Hvidovre Hospital
Kettegård Allé 30
DK-2650 Hvidovre
Denmark
Tel: +45 386 22828
E-mail: torkil@xxxxxxxx
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