Hi all, so I used the rename-bucket option this morning for OSD node renames, and it was a success. Works great even on Luminous.
I looked at the swap-bucket command and I felt it was leaning toward real data migration from old OSDs to new OSDs and I was a bit timid because there wasn’t a second host, just a name change. So when I looked at rename-bucket, it just seemed too simple not to try first. And I did, and it was. I renamed two host buckets (they housed discrete storage classes, so no dangerous loss of data redundancy), and even some rack buckets.
sudo ceph osd crush rename-bucket <oldname> <newname>
and no data moved. I first thought I’d wait til the hosts were shutdown, but after I stopped the OSDs on the nodes, it seemed safe enough, and it was.
In my particular case, I was moving migrating nodes to a new datacenter, just new names and IPs. I also moved a mon/mgr/rgw; and I merely had to delete the mon first, then reprovision it later.
The rgw and mgr worked fine. I pre-edited ceph.conf to add the new networks, remove the old mon name, add the new mon name, so on startup it worked.
I’m not a ceph admin but I play one on the tele.
From: Eugen Block <eblock@xxxxxx>
Date: Wednesday, February 15, 2023 at 12:44 AM
To: ceph-users@xxxxxxx <ceph-users@xxxxxxx>
Subject: [EXTERNAL] Re: Renaming a ceph node
Hi,
I haven't done this in a production cluster yet, only in small test
clusters without data. But there's a rename-bucket command:
ceph osd crush rename-bucket <srcname> <dstname>
rename bucket <srcname> to <dstname>
It should do exactly that, just rename the bucket within the crushmap
without changing the ID. That command also exists in Luminous, I
believe. To have an impression of the impact I'd recommend to test in
a test cluster first.
Regards,
Eugen
Zitat von Manuel Lausch <manuel.lausch@xxxxxxxx>:
> Hi,
>
> yes you can rename a node without massive rebalancing.
>
> The following I tested with pacific. But I think this should work with
> older versions as well.
> You need to rename the node in the crushmap between shutting down the
> node with the old name and starting it with the new name.
> You only must keep the ID from the node in the crushmap!
>
> Regards
> Manuel
>
>
> On Mon, 13 Feb 2023 22:22:35 +0000
> "Rice, Christian" <crice@xxxxxxxxxxx> wrote:
>
>> Can anyone please point me at a doc that explains the most
>> efficient procedure to rename a ceph node WITHOUT causing a massive
>> misplaced objects churn?
>>
>> When my node came up with a new name, it properly joined the
>> cluster and owned the OSDs, but the original node with no devices
>> remained. I expect this affected the crush map such that a large
>> qty of objects got reshuffled. I want no object movement, if
>> possible.
>>
>> BTW this old cluster is on luminous. ☹
>>
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