Hello cephers,

I run Nautilus (14.2.15)

Here is my context : each night a script take a snapshot from each RBD volume in a pool (all the disks of the VMs hosted) on my ceph production cluster. Then each snapshot is exported (rbd export-diff | rbd import-diff in SSH) towards my ceph bakup cluster.

0. Yesterday, and for the firt time, I had this error when I ran ''rbd -p MY_POOL du'' on the ceph backup cluster :
021-01-14 11:41:29.294 7f1f2fbcf0c0 -1 librbd::DiffIterate: diff_object_map: failed to load object map rbd_object_map.781776950f8dd5.000000000000b740

1. I tried to find the image concerned by the error, and I find this one, with a slight diffence with the number of the object-map :

rbd image 'MY_IMAGE':
    size 30 GiB in 7680 objects
    order 22 (4 MiB objects)
    snapshot_count: 32
    id: 781776950f8dd5
    block_name_prefix: rbd_data.781776950f8dd5
    format: 2
    features: layering, exclusive-lock, object-map, fast-diff, deep-flatten, operations
    op_features: snap-trash
    flags:
    create_timestamp: Thu Mar 19 01:00:27 2020
    access_timestamp: Thu Mar 19 01:00:27 2020
    modify_timestamp: Thu Jan 14 01:42:23 2021

2. Then I ran a check wich not show any error
rbd -p MY_POOL object-map check "MY_IMAGE"
Object Map Check: 100% complete...done.

3. Then, I still ran a rebuild
rbd -p MY_POOL object-map rebuild "MY_IMAGE"
Object Map Rebuild: 100% complete...done.

4. But the error is still here :
2021-01-15 09:33:58.775 7fa088e350c0 -1 librbd::DiffIterate: diff_object_map: failed to load object map rbd_object_map.781776950f8dd5.000000000000b740

Do someone know how to find the the image concerned by the object-map error and fix this error.

Thank you for your help,

Rafael