Hi,
Has something change with 'rbd diff' in Octopus or have I hit a bug? I am no longer able to obtain the list of objects that have changed between two snapshots of an image, it always lists all allocated regions of the RBD image. This behaviour however only occurs when I add the '--whole-object' switch.
Using KRBD client with kernel 5.11.7 and Ceph Octopus 15.2.11 as part of Proxmox PVE 6.4 which is based on Debian 10. Images have the following features and I've performed offline object map checks and rebuilds (no errors reported).
To reproduce my issue I first create a new RBD image (default features are 63), map it using KRBD, write some data, create first snapshot, write a single object (4 MiB), create a second snapshot and then list the differences:
[admin@kvm1a ~]# rbd create rbd_hdd/test --size 40G
[admin@kvm1a ~]# rbd info rbd_hdd/test
rbd image 'test':
size 40 GiB in 10240 objects
order 22 (4 MiB objects)
snapshot_count: 0
id: 73363f8443987b
block_name_prefix: rbd_data.73363f8443987b
format: 2
features: layering, exclusive-lock, object-map, fast-diff, deep-flatten
op_features:
flags:
create_timestamp: Wed May 12 23:01:11 2021
access_timestamp: Wed May 12 23:01:11 2021
modify_timestamp: Wed May 12 23:01:11 2021
[admin@kvm1a ~]# rbd map rbd_hdd/test
/dev/rbd18
[admin@kvm1a ~]# dd if=/dev/zero of=/dev/rbd18 bs=64M count=1
1+0 records in
1+0 records out
67108864 bytes (67 MB, 64 MiB) copied, 0.668701 s, 100 MB/s
[admin@kvm1a ~]# sync
[admin@kvm1a ~]# rbd snap create rbd_hdd/test@snap1
[admin@kvm1a ~]# dd if=/dev/zero of=/dev/rbd18 bs=4M count=1
1+0 records in
1+0 records out
4194304 bytes (4.2 MB, 4.0 MiB) copied, 0.265691 s, 15.8 MB/s
[admin@kvm1a ~]# sync
[admin@kvm1a ~]# rbd snap create rbd_hdd/test@snap2
[admin@kvm1a ~]# rbd diff --from-snap snap1 rbd_hdd/test@snap2 --format=json
[{"offset":0,"length":4194304,"exists":"true"}]
[admin@kvm1b ~]# rbd diff --from-snap snap1 rbd_hdd/test@snap2 --format=json --whole-object
[{"offset":0,"length":4194304,"exists":"true"},{"offset":4194304,"length":4194304,"exists":"true"},{"offset":8388608,"length":4194304,"exists":"true"},{"offset":12582912,"length":4194304,"exists":"true"},{"offset":16777216,"length":4194304,"exists":"true"},{"offset":20971520,"length":4194304,"exists":"true"},{"offset":25165824,"length":4194304,"exists":"true"},{"offset":29360128,"length":4194304,"exists":"true"},{"offset":33554432,"length":4194304,"exists":"true"},{"offset":37748736,"length":4194304,"exists":"true"},{"offset":41943040,"length":4194304,"exists":"true"},{"offset":46137344,"length":4194304,"exists":"true"},{"offset":50331648,"length":4194304,"exists":"true"},{"offset":54525952,"length":4194304,"exists":"true"},{"offset":58720256,"length":4194304,"exists":"true"},{"offset":62914560,"length":4194304,"exists":"true"}]
[admin@kvm1a ~]# rbd du rbd_hdd/test
NAME PROVISIONED USED
test@snap1 40 GiB 64 MiB
test@snap2 40 GiB 64 MiB
test 40 GiB 4 MiB
<TOTAL> 40 GiB 132 MiB
My tests appear to confirm that adding the 'whole-object' option to rbd diff results in it listing every allocated extend instead of only the changes...
Regards
David Herselman
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