Re: data corruption after rbd migration

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Hi Nikola,

I found your info a bit confusing. The first command suggests that the VM
is shut down and later you are talking about live migration. So how are you
migrating data online or offline?

In the case of live migration, I would suggest looking at the
fsfreeze(proxmox use it) command.

Hope it helps!

Best Regards,

Jaroslav Shejbal



pá 3. 11. 2023 v 9:08 odesílatel Nikola Ciprich <nikola.ciprich@xxxxxxxxxxx>
napsal:

> Dear ceph users and developers,
>
> we're struggling with strange issue which I think might be a bug
> causing snapshot data corruption while migrating RBD image
>
> we've tracked it to minimal set of steps to reproduce using VM
> with one 32G drive:
>
> rbd create --size 32768 sata/D2
> virsh create xml_orig.xml
> rbd snap create ssd/D1@snap1
> rbd export-diff ssd/D1@snap1 - | rbd import-diff - sata/D2
> rbd export --export-format 1 --no-progress ssd/D1@snap1 - | xxh64sum
> 505dde3c49775773
> rbd export --export-format 1 --no-progress sata/D2@snap1 - | xxh64sum
> 505dde3c49775773  # <- checksums match - OK
>
> virsh shutdown VM
> rbd migration prepare ssd/D1 sata/D1Z
> virsh create xml_new.xml
> rbd snap create sata/D1Z@snap2
> rbd export-diff --from-snap snap1 sata/D1Z@snap2 - | rbd import-diff -
> sata/D2
> rbd migration execute sata/D1Z
> rbd migration commit sata/D1Z
> rbd export --export-format 1 --no-progress sata/D1Z@snap2 - | xxh64sum
> 19892545c742c1de
> rbd export --export-format 1 --no-progress sata/D2@snap2 - | xxh64sum
> cc045975baf74ba8 # <- snapshosts differ
>
> OS is alma 9 based, kernel 5.15.105, CEPH 17.2.6, qemu-8.0.3
> we tried disabling VM disk caches as well as discard, to no avail.
>
> my first question is, is it correct to assume creating snapshots while live
> migrating data is safe? if so, any ideas on where the problem could be?
>
> If I could provide more info, please let me know
>
> with regards
>
> nikola ciprich
>
>
>
> --
> -------------------------------------
> Ing. Nikola CIPRICH
> LinuxBox.cz, s.r.o.
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