Hi Ilya,
That explains it. Thank you for clarification!
Tony
________________________________________
From: Ilya Dryomov <idryomov@xxxxxxxxx>
Sent: December 4, 2023 09:40 AM
To: Tony Liu
Cc: ceph-users@xxxxxxx; dev@xxxxxxx
Subject: Re: the image used size becomes 0 after export/import with snapshot
On Tue, Nov 28, 2023 at 8:18 AM Tony Liu <tonyliu0592@xxxxxxxxxxx> wrote:
>
> Hi,
>
> I have an image with a snapshot and some changes after snapshot.
> ```
> $ rbd du backup/f0408e1e-06b6-437b-a2b5-70e3751d0a26
> NAME PROVISIONED USED
> f0408e1e-06b6-437b-a2b5-70e3751d0a26@snapshot-eb085877-7557-4620-9c01-c5587b857029 10 GiB 2.4 GiB
> f0408e1e-06b6-437b-a2b5-70e3751d0a26 10 GiB 2.4 GiB
> <TOTAL> 10 GiB 4.8 GiB
> ```
> If there is no changes after snapshot, the image line will show 0 used.
>
> I did export and import.
> ```
> $ rbd export --export-format 2 backup/f0408e1e-06b6-437b-a2b5-70e3751d0a26 - | rbd import --export-format 2 - backup/test
> Exporting image: 100% complete...done.
> Importing image: 100% complete...done.
> ```
>
> When check the imported image, the image line shows 0 used.
> ```
> $ rbd du backup/test
> NAME PROVISIONED USED
> test@snapshot-eb085877-7557-4620-9c01-c5587b857029 10 GiB 2.4 GiB
> test 10 GiB 0 B
> <TOTAL> 10 GiB 2.4 GiB
> ```
> Any clues how that happened? I'd expect the same du as the source.
Hi Tony,
"rbd import" command does zero detection at 4k granularity by default.
If the "after snapshot" changes just zeroed everything in the snapshot,
such a discrepancy in "rbd du" USED column is expected.
Thanks,
Ilya
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