Hi,

just to visualize Rajat's response, ceph creates copy-on-write 
snapshots so the incremental backup doesn't really use much space. On 
a Victoria cloud I created one full backup of an almost empty volume 
(made an ext4 filesystem and mounted it, create one tiny file), then 
created a second tiny file and then made another incremental backup, 
this is what ceph sees:

ceph01:~ # rbd du <backup_pool>/volume-6662f50a-a74c-47a4-8abd-a49069f3614c
NAME                                                                   
                                           PROVISIONED  USED
volume-6662f50a-a74c-47a4-8abd-a49069f3614c@backup.650a4f8f-7b61-447e-9eb9-767c74b15342.snap.1684329174.8419683        5 GiB  192 
MiB
volume-6662f50a-a74c-47a4-8abd-a49069f3614c@backup.1d358548-5d1d-4e03-9728-bb863c717910.snap.1684329450.9599462        5 GiB   16 
MiB
volume-6662f50a-a74c-47a4-8abd-a49069f3614c                             
                                                 5 GiB      0 B
<TOTAL>

backup.650a4f8f-7b61-447e-9eb9-767c74b15342 (using 192 MiB) is the 
full backup, backup.1d358548-5d1d-4e03-9728-bb863c717910 is the 
incremental backup (using 16 MiB).

Zitat von Rajat Dhasmana <rdhasman@redhat.com>:

> Hi Satish,
>
> Did you check the size of the actual backup file in ceph storage? It should
> be created in the *backups* pool[1].
> Cinder shows the same size of incremental backup as a normal backup but
> file size should be different from
> the size shown in cinder DB records. Also file size of incremental backup
> should not be the same as the file size of full backup.
>
> [1]
> https://github.com/openstack/devstack/blob/34afa91fc9f830fc8e1fdc4d76e7aa6d4248eaaa/lib/cinder_backups/ceph#L22
>
> Thanks
> Rajat Dhasmana
>
> On Wed, May 17, 2023 at 12:25 AM Satish Patel <satish.txt@gmail.com> wrote:
>
>> Folks,
>>
>> I have ceph storage for my openstack and configure cinder-volume and
>> cinder-backup service for my disaster solution. I am trying to use the
>> cinder-backup incremental option to save storage space but somehow It
>> doesn't work the way it should work.
>>
>> Whenever I take incremental backup it shows a similar size of original
>> volume. Technically It should be smaller. Question is does ceph
>> support incremental backup with cinder?
>>
>> I am running a Yoga release.
>>
>> $ openstack volume list
>> +--------------------------------------+------------+------------+------+-------------------------------------+
>> | ID                                   | Name       | Status     | 
>> Size | Attached to                         |
>> +--------------------------------------+------------+------------+------+-------------------------------------+
>> | 285a49a6-0e03-49e5-abf1-1c1efbfeb5f2 | spatel-vol | backing-up |   
>>  10 | Attached to spatel-foo on /dev/sdc  |
>> +--------------------------------------+------------+------------+------+-------------------------------------+
>>
>> ### Create full backup
>> $ openstack volume backup create --name spatel-vol-backup spatel-vol --force
>> +-------+--------------------------------------+
>> | Field | Value                                |
>> +-------+--------------------------------------+
>> | id    | 4351d9d3-85fa-4cd5-b21d-619b3385aefc |
>> | name  | spatel-vol-backup                    |
>> +-------+--------------------------------------+
>>
>> ### Create incremental
>> $ openstack volume backup create --name spatel-vol-backup-1 
>> --incremental --force spatel-vol
>> +-------+--------------------------------------+
>> | Field | Value                                |
>> +-------+--------------------------------------+
>> | id    | 294b58af-771b-4a9f-bb7b-c37a4f84d678 |
>> | name  | spatel-vol-backup-1                  |
>> +-------+--------------------------------------+
>>
>> $ openstack volume backup list
>> +--------------------------------------+---------------------+-------------+-----------+------+
>> | ID                                   | Name                | 
>> Description | Status    | Size |
>> +--------------------------------------+---------------------+-------------+-----------+------+
>> | 294b58af-771b-4a9f-bb7b-c37a4f84d678 | spatel-vol-backup-1 | None 
>>        | available |   10 |
>> | 4351d9d3-85fa-4cd5-b21d-619b3385aefc | spatel-vol-backup   | None 
>>        | available |   10 |
>> +--------------------------------------+---------------------+-------------+-----------+------+
>>
>>
>> My incremental backup still shows 10G size which should be lower 
>> compared to the first backup.
>>
>>
>>