[DRBD-user] Deleting deployed snapshot question

[kvaps]

Indeed, just checked what is happening on the backing level:

before removing snapshot I have snapshot chain like:

aaa <-- snap1 <-- bbb

where `snap1` is snapshot of `aaa`, and `bbb` is snapshot of `snap1`

but after removing `snap1` from the linstor I have two fully separated
resources: `aaa` and `bbb`, where `bbb` have no origin anymore and
does not referenced to `aaa` anymore.

- kvaps

On Sun, May 26, 2019 at 10:43 AM Gianni Milo <gianni.milo22 at gmail.com> wrote:
>
> Don't think it's a bug. In my setup I'm using ZFS as storage backend. When repeating steps you described, ZFS complains and it does not delete the snapshot, as the newly created clone depends on it. This by it's turn propagates above to the LINSTOR layer, which eventually aborts the action.
> In the case you are using LVMThin, I think lvm *does* allow deleting the snapshot, since it works differently than ZFS in this matter (data from the deleted snapshot is automatically merged into the newly created volume, so there's no dependency between them). You can verify if this is the case by doing same tests directly on the lvm layer. In any case LINSTOR relies on storage backend utils output and it does not by default prevent snapshot removal.
>
>
> On Sun, 26 May 2019 at 00:49, kvaps <kvapss at gmail.com> wrote:
>>
>> Hi
>>
>> I have a question and I can't fully determine is that bug or not.
>>
>> Example I have image A:
>>
>> linstor rd c A
>> linstor vd c aaa 1G
>> linstor r c aaa --auto-place 2
>>
>> now I can create new snapshot:
>>
>> linstor s c aaa snap1
>>
>> and deploy new resource from this snapshot:
>>
>> linstor rd c bbb
>> linstor s vd rst --from-resource aaa --from-snapshot snap1 --to-resource bbb
>> linstor s r rst --from-resource aaa --from-snapshot snap1 --to-resource bbb
>>
>> after that I can remove the snapshot:
>>
>> linstor s d aaa snap1
>>
>> Is that ok? Shouldn't it throw an error due having childrens?
>>
>>
>> - kvaps
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