Re: [ceph-users] Error when I compare hashes of export-diff / import-diff
Le 12/06/2019 à 16:01, Jason Dillaman a écrit :
On Wed, Jun 12, 2019 at 9:50 AM Rafael Diaz Maurin
wrote:
Hello Jason,
Le 11/06/2019 à 15:31, Jason Dillaman a écrit :
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 feature discard=on is activated, and qemu-guest-agent is running on
the guest.
Here are the only differences between the 2 outputs of the "rbd diff
--format plain" (image source and image destination) :
Offset Length Type
121c121
< 14103347200 2097152 data
---
> 14103339008 2105344 data
153c153
< 14371782656 2097152 data
---
> 14369685504 4194304 data
216c216
< 14640218112 2097152 data
---
> 14638120960 4194304 data
444c444
< 15739125760 2097152 data
---
> 15738519552 2703360 data
And the hashes of the exports are identical (between source and
destination) :
rbd -p ${POOL-SOURCE} export ${KVM-IMAGE}@${TODAY-SNAP} - | md5sum
=> ee7012e14870b36e7b9695e52c417c06
rbd -c ${BACKUP-CLUSTER} -p ${POOL-DESTINATION} export
${KVM-IMAGE}@${TODAY-SNAP} - | md5sum
=> ee7012e14870b36e7b9695e52c417c06
So do you think this can be caused by the fstrim/discard feature.
You said you weren't using fstrim/discard.
In fact, the daemon fstrim is not enabled in the guest, but... in
proxmox I set the option discard=on and maybe I ran fstrim once by hard
testing...
If you export both images
and compare those image extents where the diffs are different, is it
just filled w/ zeroes?
I can't find how to to compare if the diffs of the extends are filled by
w/ zeros.
However I finally succeed getting identical the "rbd diff " hashes with
the option "--whole-object" like this :
HASH source :
rbd diff --from-snap /@ --format json
--whole-object | md5sum | cut -d ' ' -f 1
Hash destination
rbd -c diff --from-snap
/@ --format json --whole-object | md5sum | cut -d '
' -f 1
Best regards,
Rafael
--
Rafael Diaz Maurin
DSI de l'Université de Rennes 1
Pôle Infrastructures, équipe Systèmes
02 23 23 71 57
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Description: Signature cryptographique S/MIME
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Re: [ceph-users] Error when I compare hashes of export-diff / import-diff
Hello Jason,
Le 11/06/2019 à 15:31, Jason Dillaman a écrit :
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 feature discard=on is activated, and qemu-guest-agent is running on
the guest.
Here are the only differences between the 2 outputs of the "rbd diff
--format plain" (image source and image destination) :
Offset Length Type
121c121
< 14103347200 2097152 data
---
> 14103339008 2105344 data
153c153
< 14371782656 2097152 data
---
> 14369685504 4194304 data
216c216
< 14640218112 2097152 data
---
> 14638120960 4194304 data
444c444
< 15739125760 2097152 data
---
> 15738519552 2703360 data
And the hashes of the exports are identical (between source and
destination) :
rbd -p ${POOL-SOURCE} export ${KVM-IMAGE}@${TODAY-SNAP} - | md5sum
=> ee7012e14870b36e7b9695e52c417c06
rbd -c ${BACKUP-CLUSTER} -p ${POOL-DESTINATION} export
${KVM-IMAGE}@${TODAY-SNAP} - | md5sum
=> ee7012e14870b36e7b9695e52c417c06
So do you think this can be caused by the fstrim/discard feature.
In fact, when fstrim/discard activated it, the only way to validate the
export-diff is to compare full exports hashes ?
Thank you.
Best regards,
Rafael
--
Rafael Diaz Maurin
DSI de l'Université de Rennes 1
Pôle Infrastructures, équipe Systèmes
02 23 23 71 57
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Description: Signature cryptographique S/MIME
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[ceph-users] Error when I compare hashes of export-diff / import-diff
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}
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
smime.p7s
Description: Signature cryptographique S/MIME
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