On Tue, Jun 11, 2019 at 9:25 AM Rafael Diaz Maurin
<Rafael.DiazMaurin@xxxxxxxxxxxxxxx> wrote:
>
> Hello,
>
> I have a problem when I want to validate (using md5 hashes) rbd
> export/import diff from a rbd source-pool (the production pool) towards
> another rbd destination-pool (the backup pool).
>
> Here is the algorythm :
> 1- First of all, I validate that the two hashes from lasts snapshots
> source and destination are the same :
> rbd -p ${POOL-SOURCE} export ${KVM-IMAGE}@${LAST-SNAP} - | md5sum
> => 3f54626da234730eefc27ef2a3b6ca83
> rbd -c ${BACKUP-CLUSTER} -p ${POOL-DESTINATION} export
> ${KVM-IMAGE}@${LAST-SNAP} - | md5sum
> => 3f54626da234730eefc27ef2a3b6ca83
>
>
> 2- If not exists, I create an empty image in the destination pool
> rbd -c ${BACKUP-CLUSTER} create ${POOL-DESTINATION}/${KVM-IMAGE} -s 1
>
> 3- I create a snapshot inside the source pool
> rbd snap create ${POOL-SOURCE}/${KVM-IMAGE}@${TODAY-SNAP}
>
> 4- I export the snapshot from the source pool and I import the snapshot
> towards the destination pool (in the pipe)
> rbd export-diff --from-snap ${LAST-SNAP}
> ${POOL-SOURCE}/${KVM-IMAGE}@${TODAY-SNAP} - | rbd -c ${BACKUP-CLUSTER}
> import-diff - ${POOL-DESTINATION}/${KVM-IMAGE}
What's the actual difference between the "rbd diff" outputs? There is
a known "issue" where object-map will flag an object as dirty if you
had run an fstrim/discard on the image, but it doesn't affect the
actual validity of the data.
> The problem occurs when I want to validate only the diff between the 2
> snapshots (in order to be more efficient). I note that those hashes are
> differents.
>
> Here is how I calcultate the hashes :
> Source-hash : rbd diff --from-snap ${LAST-SNAP}
> ${POOL-SOURCE}/${KVM-IMAGE}@${TODAY-SNAP} --format json | md5sum | cut
> -d ' ' -f 1
> => bc56663b8ff01ec388598037a20861cf
> Destination-hash : rbd -c ${BACKUP-CLUSTER} diff --from-snap
> ${LAST-SNAP} ${POOL-DESTINATION}/${KVM-IMAGE}@${TODAY-SNAP} --format
> json | md5sum | cut -d ' ' -f 1
> => 3aa35362471419abe0a41f222c113096
>
> In an other hand, if I compare the hashes of the export (between source
> and destination), they are the same :
>
> rbd -p ${POOL-SOURCE} export ${KVM-IMAGE}@${TODAY-SNAP} - | md5sum
> => 2c4962870fdd67ca758c154760d9df83
> rbd -c ${BACKUP-CLUSTER} -p ${POOL-DESTINATION} export
> ${KVM-IMAGE}@${TODAY-SNAP} - | md5sum
> => 2c4962870fdd67ca758c154760d9df83
>
>
> Can someone has an idea of what's happenning ?
>
> Can someone has a way to succeed in comparing the export-diff /import-diff ?
>
>
>
>
> Thank you,
> Rafael
>
> --
> Rafael Diaz Maurin
> DSI de l'Université de Rennes 1
> Pôle Infrastructures, équipe Systèmes
> 02 23 23 71 57
>
>
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--
Jason
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