Ceph RBD Image Usage After Creating Snapshot

[azuresnow]

In the Ceph Squid, I created the RBD image of 200GB in Ceph Mgr Dashboard.
And I mounted that RBD image and stored the data of 10GB. Then the dashboard shows the usage as 5%.
And then I created the snapshot of that RBD image. Then the dashboard shows the RBD image usage as 0% even though there are 10GB data in that RBD image.

I checked the RBD image usage using rbd du command on CLI and rbd du shows 0 bytes.
Why does it show 0 bytes after creating the snapshot on the RBD image still having 10GB data?
Is it correct or wrong misconfigured?

 

[Sviat]

Hi,

During creation a snapshot of an RBD image, Ceph moves all existing data into the snapshot’s reference.
The live image now has no unique blocks, so rbd du and the dashboard correctly show 0 bytes for the image.
Your 10 GB is still stored, but it’s accounted entirely under the snapshot.
This is normal copy‑on‑write behavior, not a misconfiguration.