Ceph RBD Volume Migration #12820

problem

Volume migration between Ceph RBD primary storages fails in CloudStack 4.22 because the destination is incorrectly treated as a local file path instead of an RBD URI.

In CloudStack 4.22, migrating a volume from one Ceph RBD primary storage to another fails during the qemu-img convert operation.

The system attempts a direct primary-to-primary migration (which is expected behavior in newer versions), but the destination is incorrectly passed as a local filesystem path instead of an RBD URI.

As a result, the migration fails with:
qemu-img: CEPH2_NVME/.raw: error while converting raw:
Could not create 'CEPH2_NVME/.raw': No such file or directory

From the agent logs:
qemu-img convert -O raw -U
rbd:CEPH1_SATA/:mon_host=...:auth_supported=cephx:id=...
CEPH2_NVME/.raw

Expected behavior:
qemu-img convert -O raw
rbd:CEPH1_SATA/
rbd:CEPH2_NVME/

The destination is missing the rbd: prefix and is incorrectly suffixed with .raw, causing qemu-img to treat it as a local file path.

versions

•	Apache CloudStack: 4.22.0
•	Hypervisor: KVM
•	OS: Ubuntu 22.04 and 24.04
•	qemu-img version: 6.2.0 (Debian 1:6.2+dfsg-2ubuntu6.27)
•	Ceph version: Source: Octopus / Destination: Reef

The steps to reproduce the bug

1.	Configure two Ceph RBD primary storages in the same zone:
•	Source: CEPH1
•	Destination: CEPH2
2.	Ensure both are accessible from KVM hosts.
3.	Create a volume in CEPH1
4.	Attempt to migrate the volume to CEPH2 using:
•	CloudStack UI
             select volume -> click on Migrate Volume -> Select CEPH2 storage pool

•	cmk call
              migrate volume storageid=CEPH2_ID volumeid=VOLUME_ID_HOSTED_IN_CEPH1

5.	Observe failure during migration.

What to do about it?

•	Ensure the destination is correctly formatted as an RBD URI (rbd:pool/image)
•	Validate logic in LibvirtStorageAdaptor (KVM) for RBD-to-RBD migration path
•	Possibly introduce fallback to secondary storage if direct conversion fails