Enable pool level replication using type snapshot

[roosterfish]

Hi, from the docs it was not clear how to enable replication using type snapshot so I ended up trying to enable it on pool level which (according to upstream docs) looks to be not supported.

However MicroCeph allows running the following command to enable replication using type snapshot on pool level:

microceph replication enable rbd foo --type snapshot --remote secondary

But instead the command seems to trigger the setup of --type journal instead as pre-existing volumes of the pool foo now have the journaling feature enabled and their mirroring mode (rbd info foo/test) also displays mirroring mode: journal.

I have tested using MicroCeph squid/stable. Those are the reproducer steps on the two Ceph clusters micro01 and micro02:

# micro01

microceph cluster bootstrap
microceph disk add /dev/sdb /dev/sdc /dev/sdd
microceph remote import secondary <token from micro02> --local-name primary
microceph cluster export secondary

microceph enable rbd-mirror
ceph osd pool create foo 32
rbd pool init foo

rbd create foo/test --size 10M
rbd create foo/test2 --size 10M

root@micro01:~# rbd info foo/test
rbd image 'test':
	size 10 MiB in 3 objects
	order 22 (4 MiB objects)
	snapshot_count: 0
	id: 375c50cac2b3
	block_name_prefix: rbd_data.375c50cac2b3
	format: 2
	features: layering, exclusive-lock, object-map, fast-diff, deep-flatten
	op_features: 
	flags: 
	create_timestamp: Fri Apr 25 07:15:51 2025
	access_timestamp: Fri Apr 25 07:15:51 2025
	modify_timestamp: Fri Apr 25 07:15:51 2025

microceph replication enable rbd foo --type snapshot --remote secondary # fails without error

root@micro01:~# rbd info foo/test
rbd image 'test':
	size 10 MiB in 3 objects
	order 22 (4 MiB objects)
	snapshot_count: 0
	id: 375c50cac2b3
	block_name_prefix: rbd_data.375c50cac2b3
	format: 2
	features: layering, exclusive-lock, object-map, fast-diff, deep-flatten, journaling
	op_features: 
	flags: 
	create_timestamp: Fri Apr 25 07:15:51 2025
	access_timestamp: Fri Apr 25 07:15:51 2025
	modify_timestamp: Fri Apr 25 07:15:51 2025
	journal: 375c50cac2b3
	mirroring state: enabled
	mirroring mode: journal
	mirroring global id: aab836e6-8046-4921-8c3f-de7f7e13e59b
	mirroring primary: true

# micro02

microceph cluster bootstrap
microceph disk add /dev/sdb /dev/sdc /dev/sdd
microceph cluster export primary
microceph remote import primary <token from micro01> --local-name secondary

microceph enable rbd-mirror
ceph osd pool create foo 32
rbd pool init foo

[syncronize-issues-to-jira[bot]]

Thank you for reporting your feedback to us!

The internal ticket has been created: https://warthogs.atlassian.net/browse/CEPH-1268.

This message was autogenerated

[panagiotisevaggelou]

Hi @roosterfish ,

I've submitted a fix for this issue that adds a validation check to prevent enabling snapshot-based replication on RBD pools. Instead of silently falling back to journal mode, the command now returns a clear error message.

Open to any feedback. Thanks!

[UtkarshBhatthere]

The fix should be available in squid/edge now. Thanks @roosterfish and @panagiotisevaggelou 🙌🏼