Thanks Frank,
I don’t have too much experience editing crush rules, but I assume the chooseleaf step
would also have to change to:
step chooseleaf firstn 0 type chassis
Correct? Is that the only other change that is needed? It looks like the rule change can
happen both inside and outside the “norebalance” setting (again with CLI commands), but is
it safer to do it inside (ie. while not rebalancing)?
If I keep a backup of the crush rule map (with “ceph osd getcrushmap”), I assume I can
restore the old map if something goes bad?
Thanks again!
George
On Jun 3, 2020, at 5:24 PM, Frank Schilder
<frans(a)dtu.dk> wrote:
You can use the command-line without editing the crush map. Look at the documentation of
commands like
ceph osd crush add-bucket ...
ceph osd crush move ...
Before starting this, set "ceph osd set norebalance" and unset after you are
happy with the crush tree. Let everything peer. You should see misplaced objects and
remapped PGs, but no degraded objects or PGs.
Do this only when cluster is helth_ok, otherwise things can get really complicated.
Best regards,
=================
Frank Schilder
AIT Risø Campus
Bygning 109, rum S14
________________________________________
From: Kyriazis, George <george.kyriazis(a)intel.com>
Sent: 03 June 2020 22:45:11
To: ceph-users
Subject: [ceph-users] Best way to change bucket hierarchy
Helo,
I have a live ceph cluster, and I’m in the need of modifying the bucket hierarchy. I am
currently using the default crush rule (ie. keep each replica on a different host). My
need is to add a “chassis” level, and keep replicas on a per-chassis level.
From what I read in the documentation, I would have to edit the crush file manually,
however this sounds kinda scary for a live cluster.
Are there any “best known methods” to achieve that goal without messing things up?
In my current scenario, I have one host per chassis, and planning on later adding nodes
where there would be >1 hosts per chassis. It looks like “in theory” there wouldn’t be
a need for any data movement after the crush map changes. Will reality match theory?
Anything else I need to watch out for?
Thank you!
George
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