[ceph-users] Adding multiple OSD

David Turner drakonstein at gmail.com
Mon Dec 4 11:36:33 PST 2017


No, I would only add disks to 1 failure domain at a time.  So in your
situation where you're adding 2 more disks to each node, I would recommend
adding the 2 disks into 1 node at a time.  Your failure domain is the
crush-failure-domain=host.  So you can lose a host and only lose 1 copy of
the data.  If all of your pools are using the k=5 m=3 profile, then I would
say it's fine to add the disks into 2 nodes at a time.  If you have any
replica pools for RGW metadata or anything, then I would stick with the 1
host at a time.

On Mon, Dec 4, 2017 at 2:29 PM Karun Josy <karunjosy1 at gmail.com> wrote:

> Thanks for your reply!
>
> I am using erasure coded profile with k=5, m=3 settings
>
> $ ceph osd erasure-code-profile get profile5by3
> crush-device-class=
> crush-failure-domain=host
> crush-root=default
> jerasure-per-chunk-alignment=false
> k=5
> m=3
> plugin=jerasure
> technique=reed_sol_van
> w=8
>
>
> Cluster has 8 nodes, with 3 disks each. We are planning to add 2 more on
> each nodes.
>
> If I understand correctly, then I can add 3 disks at once right , assuming
> 3 disks can fail at a time as per the ec code profile.
>
> Karun Josy
>
> On Tue, Dec 5, 2017 at 12:06 AM, David Turner <drakonstein at gmail.com>
> wrote:
>
>> Depending on how well you burn-in/test your new disks, I like to only add
>> 1 failure domain of disks at a time in case you have bad disks that you're
>> adding.  If you are confident that your disks aren't likely to fail during
>> the backfilling, then you can go with more.  I just added 8 servers (16
>> OSDs each) to a cluster with 15 servers (16 OSDs each) all at the same
>> time, but we spent 2 weeks testing the hardware before adding the new nodes
>> to the cluster.
>>
>> If you add 1 failure domain at a time, then any DoA disks in the new
>> nodes will only be able to fail with 1 copy of your data instead of across
>> multiple nodes.
>>
>> On Mon, Dec 4, 2017 at 12:54 PM Karun Josy <karunjosy1 at gmail.com> wrote:
>>
>>> Hi,
>>>
>>> Is it recommended to add OSD disks one by one or can I add couple of
>>> disks at a time ?
>>>
>>> Current cluster size is about 4 TB.
>>>
>>>
>>>
>>> Karun
>>> _______________________________________________
>>> ceph-users mailing list
>>> ceph-users at lists.ceph.com
>>> http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
>>>
>>
>
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