Incremental snapshot from RBD and Cephfs by ceph-csi

[mehdi-aghayari]

Is there any solution for Incremental snapshot from RBD and Cephfs?
I need take full snapshot at every on Saturday. also take incremental snapshot on other weekdays.

[Rakshith-R]

Hey @mehdi-aghayari ,

I'll split the discussion into two parts: RBD & CephFS:

RBD Incremental Snapshots:

• RBD images has layering feature, therefore it does not consume extra memory when you take a snapshot each time.
• When you take a snapshot (upto 250, flattening kicks in after this limit), you virtually don't consumer any extra space.
• Therefore, you can consider each snapshot to just consist of incremental changes.
• Coming to accessing such diffs for backup purposes, there is a kep changed block tracking feature that should make this possible soon
• Currently, it is not possible to obtain such diffs manually through rbd api. Support for this is being added in "rbd du "command updated to count actual total used space by an image ceph#60844 (comment) .

[Rakshith-R]

CephFS incremental Snapshots:

• CephFS snapshots are incremental in nature too, however, restoring those snapshots aka cloning is an expensive process.
• CephFS clones are full copy and may take a lot of time depending on number of files etc
• CephFS shallow clones that directly mount the CephFS snapshot in read only mode should be preferred for use here. refer shallow-clones-design.
• Just restoring a PVC in ROX mode from a snapshot will give you a shallow CephFS clone.
• Coming to accessing such diffs for backup purposes, you can only do it manually using cephfs snap diff api. refer croit's blog on it for more details.