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List:       vdsm-devel
Subject:    =?utf-8?q?=5Bovirt-devel=5D?= [storage] how to find if a snapshot is in preview based on storage dom
From:       Germano Veit Michel <germano () redhat ! com>
Date:       2020-08-21 1:33:24
Message-ID: CANHSq5DfE6kG-NBXwmkbRaSuiFR+oW85fCbjWOnkE1A-dPq7jA () mail ! gmail ! com
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Hi,

Is there a reliable way to figure out if a snapshot is in preview only
using information obtained from the storage domain metadata?
I'm trying to find a way to distinguish a problematic snapshot chain
(double parent) from a snapshot in preview in order to improve dump-volume
chains.

Currently dump-volume-chains throws an error (DuplicateParentError) if a
snapshot is in preview for the image, as there is a 'Y' shape split in the
chain
with 2 volumes (previous chain + preview) pointing to a common parent:

   image:    dff0a0c0-b731-4e5b-9f32-d97310ca40de

             Error: more than one volume pointing to the same parent volume
e.g: (_BLANK_UUID<-a), (a<-b), (a<-c)

             Unordered volumes and children:

             - e6c7bec0-53c6-4729-a4a0-a9b3ef2b8c38 <-
5eb2b29d-82d6-4337-8511-3c86705d566e
               status: OK, voltype: LEAF, format: COW, legality: LEGAL,
type: SPARSE, capacity: 1073741824, truesize: 1073741824

             - e0475853-4514-4464-99e7-b185cce9b67d <-
deceff83-9d88-4f87-8304-d5bf74d119b1
               status: OK, voltype: LEAF, format: COW, legality: LEGAL,
type: SPARSE, capacity: 1073741824, truesize: 1073741824

             - e6c7bec0-53c6-4729-a4a0-a9b3ef2b8c38 <-
e0475853-4514-4464-99e7-b185cce9b67d
               status: OK, voltype: INTERNAL, format: COW, legality: LEGAL,
type: SPARSE, capacity: 1073741824, truesize: 1073741824

             - 00000000-0000-0000-0000-000000000000 <-
e6c7bec0-53c6-4729-a4a0-a9b3ef2b8c38
               status: OK, voltype: INTERNAL, format: RAW, legality: LEGAL,
type: PREALLOCATED, capacity: 1073741824, truesize: 1073741824

From the engine side it's easy, but I'd need to solve this problem using
only metadata from the storage.

The only thing I could think of is that one of the volumes pointing to the
common parent has voltype LEAF. Any better ideas?

Thanks,
Germano

[Attachment #5 (text/html)]

<div dir="ltr"><div>Hi,</div><div><br></div><div>Is there a reliable way to figure \
out if a snapshot is in preview only using information obtained from the storage \
domain metadata?</div><div></div><div>I&#39;m trying to find a way to distinguish a \
problematic snapshot chain (double parent) from a snapshot in preview in order to \
improve dump-volume chains.<br></div><div></div><div><br></div><div>Currently \
dump-volume-chains throws an error (DuplicateParentError) if a snapshot is in preview \
for the image, as there is a &#39;Y&#39; shape split in the chain</div><div>with 2 \
volumes (previous chain + preview) pointing to a common \
parent:<br></div><div><br></div><div>     image:      \
dff0a0c0-b731-4e5b-9f32-d97310ca40de<br><br>                    Error: more than one \
volume pointing to the same parent volume e.g: (_BLANK_UUID&lt;-a), (a&lt;-b), \
(a&lt;-c)<br><br>                    Unordered volumes and children:<br><br>          \
- e6c7bec0-53c6-4729-a4a0-a9b3ef2b8c38 &lt;- 5eb2b29d-82d6-4337-8511-3c86705d566e<br> \
status: OK, voltype: LEAF, format: COW, legality: LEGAL, type: SPARSE, capacity: \
1073741824, truesize: 1073741824<br><br>                    - \
e0475853-4514-4464-99e7-b185cce9b67d &lt;- deceff83-9d88-4f87-8304-d5bf74d119b1<br>   \
status: OK, voltype: LEAF, format: COW, legality: LEGAL, type: SPARSE, capacity: \
1073741824, truesize: 1073741824<br><br>                    - \
e6c7bec0-53c6-4729-a4a0-a9b3ef2b8c38 &lt;- e0475853-4514-4464-99e7-b185cce9b67d<br>   \
status: OK, voltype: INTERNAL, format: COW, legality: LEGAL, type: SPARSE, capacity: \
1073741824, truesize: 1073741824<br><br>                    - \
00000000-0000-0000-0000-000000000000 &lt;- e6c7bec0-53c6-4729-a4a0-a9b3ef2b8c38<br>   \
status: OK, voltype: INTERNAL, format: RAW, legality: LEGAL, type: PREALLOCATED, \
capacity: 1073741824, truesize: 1073741824</div><div><br></div><div>From the engine \
side it&#39;s easy, but I&#39;d need to solve this problem using only metadata from \
the storage.</div><div><br></div><div>The only thing I could think of is that one of \
the volumes pointing to the common parent has voltype LEAF. Any better \
ideas?<br></div><div></div><div><br></div><div>Thanks,</div><div>Germano</div><div><br></div></div>



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