Bug 2101774

Summary: [RFE][rbd-mirror] : rbd mirror image status for snapshot based mirroring to provide info on last 100% synced snapshot to current time
Product: [Red Hat Storage] Red Hat Ceph Storage Reporter: Vasishta <vashastr>
Component: RBD-MirrorAssignee: Ilya Dryomov <idryomov>
Status: NEW --- QA Contact:
Severity: low Docs Contact:
Priority: unspecified    
Version: 5.1CC: ceph-eng-bugs, cephqe-warriors, jdurgin
Target Milestone: ---Keywords: FutureFeature
Target Release: 7.1   
Hardware: Unspecified   
OS: Unspecified   
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Description Vasishta 2022-06-28 11:01:46 UTC 
Description of problem:
Currently rbd-mirror image status doesn't depict how many snapshots are in queue. In our observations, some images were behind 3 snapshot to be synced.
RBD image status doesn't reflect the same.

It would be nice to display information on current different between last snapshot 100% copied snapshot and current time.
Or image status could depict that the mirror image snapshot queue has more than 1 image.

This would be helpful for users to compare it with their RPO.

Version-Release number of selected component (if applicable):
<latest>

Steps to Reproduce:
1. Configure snapshot based mirroring b/w two clusters.
2. Deploy agressive IOs on images or try to have controlled lesser IOs b/w two clusters.
3. check rbd snap ls --all on images in primary -
there would be queue of 3-5 snaps for some of the images
check snap ls --all on secondary, there would be two snapshots, one 100% copied, and one in progress which could be copy of one of a snapshot in queue of primary.
4. check rbd image status at both primay and secondary. Image status doesn't information on time since last 100% copied snapshot.

Actual results: and Expected results:
(Explained above)