Re: How can I clone data from a faulty bluestore disk?

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Hi,

I think that the approach with exporting and importing PGs would be
a-priori more successful than the one based on pvmove or ddrescue. The
reason is that you don't need to export/import all data that the
failed disk holds, but only the PGs that Ceph cannot recover
otherwise. The logic here is that these are, likely, not the same PGs
due to which tools are crashing.

that makes sense.

Thanks!

Zitat von "Alexander E. Patrakov" <patrakov@xxxxxxxxx>:

Hi,

I think that the approach with exporting and importing PGs would be
a-priori more successful than the one based on pvmove or ddrescue. The
reason is that you don't need to export/import all data that the
failed disk holds, but only the PGs that Ceph cannot recover
otherwise. The logic here is that these are, likely, not the same PGs
due to which tools are crashing.

Note that after the export/import operation Ceph might still think "I
need a copy from that failed disk and not the one that you gave me",
in this case just export a copy of the same PG from the other failed
OSD and import elsewhere, up to the total number of copies. If even
that desn't help, "ceph osd lost XX" would be the last (very
dangerous) words to convince Cepth that osd.XX will not be seen in the
future.

On Sat, Feb 3, 2024 at 5:35 AM Eugen Block <eblock@xxxxxx> wrote:

Hi,

if the OSDs are deployed as LVs (by ceph-volume) you could try to do a
pvmove to a healthy disk. There was a thread here a couple of weeks
ago explaining the steps. I don’t have it at hand right now, but it
should be easy to find.
Of course, there’s no guarantee that this will be successful. I also
can’t tell if Igor‘s approach is more promising.

Zitat von Igor Fedotov <igor.fedotov@xxxxxxxx>:

> Hi Carl,
>
> you might want to use ceph-objectstore-tool to export PGs from
> faulty OSDs and import them back to healthy ones.
>
> The process could be quite tricky though.
>
> There is also pending PR (https://github.com/ceph/ceph/pull/54991)
> to make the tool more tolerant to disk errors.
>
> The patch worth trying in some cases, not a silver bullet though.
>
> And generally whether the recovery doable greatly depends on the
> actual error(s).
>
>
> Thanks,
>
> Igor
>
> On 02/02/2024 19:03, Carl J Taylor wrote:
>> Hi,
>> I have a small cluster with some faulty disks within it and I want to clone
>> the data from the faulty disks onto new ones.
>>
>> The cluster is currently down and I am unable to do things like
>> ceph-bluestore-fsck but ceph-bluestore-tool  bluefs-export does appear to
>> be working.
>>
>> Any help would be appreciated
>>
>> Many thanks
>> Carl
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--
Alexander E. Patrakov


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