Bug 2045094 - [rbd-mirror] : mirror image status - snapshot - each element needs to be consistent with each other - bytes_per_second and replay_state
Summary: [rbd-mirror] : mirror image status - snapshot - each element needs to be cons...
Keywords:
Status: NEW
Alias: None
Product: Red Hat Ceph Storage
Classification: Red Hat Storage
Component: RBD-Mirror
Version: 5.0
Hardware: Unspecified
OS: Unspecified
unspecified
low
Target Milestone: ---
: 8.0
Assignee: Ilya Dryomov
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Depends On:
Blocks:
TreeView+ depends on / blocked
 
Reported: 2022-01-25 15:26 UTC by Vasishta
Modified: 2023-07-31 21:50 UTC (History)
4 users (show)

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Red Hat Issue Tracker RHCEPH-3041 0 None None None 2022-01-25 15:40:27 UTC

Description Vasishta 2022-01-25 15:26:54 UTC
Description of problem:
in mirror image status, each element needs to be consistent with each other
Example - bytes_per_second and replay_state

As per understanding, bytes_per_second refers to the speed at which sync is happening and replay_state is the status of sync
replay_state should be idle only when sync is done, i,e bytes_per_second reaches zero

Version-Release number of selected component (if applicable):
16.2.0-146.el8cp

How reproducible:
Have tried in 4.3, it was reproducible

Steps to Reproduce:
1. Configure snapshot based mirroring
2. add some data into an image and take a mirror snapshot
3. observe mirror image status at secondary site

Actual results:
$ sudo rbd mirror image status two_way_rep_snapshot_image/image01
image01:
  global_id:   40118ceb-d5a1-4079-bfeb-89375e23e681
  state:       up+replaying
  description: replaying, {"bytes_per_second":244032232.73,"bytes_per_snapshot":2684354560.0,"local_snapshot_timestamp":1643123739,"remote_snapshot_timestamp":1643123739,"replay_state":"idle"}

Expected results:
bytes_per_second should be zero by the time reply state is reported as idle

Additional info:
Observed this for images of various sizes from 1G to 50G, snapshot sync and  complete resync

Comment 1 Sunny Kumar 2022-05-19 12:55:27 UTC
Hi Vasishta,

You might observe some delay because the stats actually get updated after it re-scans the image. Which is basically needed to calculate the average number of bytes got copied per snapshot.

Hope this helps.
Thanks,
Sunny

Comment 2 Vasishta 2022-05-19 13:04:32 UTC
Hi Sunny,

Thanks for the insights on the slight delay in the update of bytes_per_second.
Though I agree that the delay very small, I think it would be a nice thing if we can bring co-ordination between related stats if bytes_per_second is a metric that denotes the data being copied from the peer cluster.

Regards,
Vasishta


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