9 Jun
2020
9 Jun
'20
6:42 a.m.
Hi all
We are looking at implementing Ceph/CephFS for a project. Over time, we may wish to add
additional replicas to our cluster. If we modify a CRUSH map, is there a way of then
requesting Ceph to re-evaluate the placement of objects across the cluster according to
the modified CRUSH map?
Brett
9 Jun
9 Jun
7:20 a.m.
This is done automatically. Every time the crush map changes, objects get moved around.
Therefore, a typical procedure is
- make sure ceph is HEALTH_OK
- ceph osd set noout
- ceph osd set norebalance
- edit crush map
- wait for peering to finish, all PGs must be active+clean
- lots of PGs will also be re-mapped
- ceph osd unset norebalance
- ceph osd unset noout
Before doing the last 2 steps, verify that no PGs are incomplete and no objects are
degraded. Otherwise, fix first.
Best regards,
=================
Frank Schilder
AIT Risø Campus
Bygning 109, rum S14
________________________________________
From: Brett Randall <brett.randall(a)gmail.com>
Sent: 09 June 2020 07:42:33
To: ceph-users(a)ceph.io
Subject: [ceph-users] Rebalancing after modifying CRUSH map
Hi all
We are looking at implementing Ceph/CephFS for a project. Over time, we may wish to add
additional replicas to our cluster. If we modify a CRUSH map, is there a way of then
requesting Ceph to re-evaluate the placement of objects across the cluster according to
the modified CRUSH map?
Brett
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7:21 a.m.
Den tis 9 juni 2020 kl 07:43 skrev Brett Randall <brett.randall(a)gmail.com>om>:
Hi all
We are looking at implementing Ceph/CephFS for a project. Over time, we
may wish to add additional replicas to our cluster. If we modify a CRUSH
map, is there a way of then requesting Ceph to re-evaluate the placement of
objects across the cluster according to the modified CRUSH map?
If you edit the crush map (including just adding a disk or a new host) then
all the pools whose crushrules are affected by the change will more or less
immediately try to move around data in order to fit the new crush map. If
you ask the cluster to move in some impossible way, it will refuse and
claim the PGs are misplaced/remapped but will still continue to serve data
as usual, until you either make it possible to place after the new rules,
or you revert the new rules.
--
May the most significant bit of your life be positive.
10 Jun
10 Jun
1:19 a.m.
Thanks Janne, this is fantastic to know.
Brett
--- original message ---
On June 9, 2020, 4:21 PM GMT+10 icepic.dz(a)gmail.com wrote:
Den tis 9 juni 2020 kl 07:43 skrev Brett Randall <brett.randall(a)gmail.com>om>:
> Hi all
> We are looking at implementing Ceph/CephFS for a
project. Over time, we may wish to add additional replicas to our cluster. If we modify a
CRUSH map, is there a way of then requesting Ceph to re-evaluate the placement of objects
across the cluster according to the modified CRUSH map?
If you edit the crush map (including just adding a disk or a new host) then all the pools
whose crushrules are affected by the change will more or less immediately try to move
around data in order to fit the new crush map. If you ask the cluster to move in some
impossible way, it will refuse and claim the PGs are misplaced/remapped but will still
continue to serve data as usual, until you either make it possible to place after the new
rules, or you revert the new rules.
--
May the most significant bit of your life be positive.
--- end of original message ---
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days inactive
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3 comments
3 participants
participants (3)
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Brett Randall -
Frank Schilder -
Janne Johansson