[Gluster-devel] Snapshot aware Geo-replication

[Amar Tumballi]

Can we re-visit this thread?

Aravinda, Would be great to add it to github issues, so we can pursue this
forward there.

-Amar

On Tue, Apr 5, 2016 at 2:48 PM, Aravinda <avishwan at redhat.com> wrote:

> Hi,
>
> Gluster Snapshots and Geo-replication are not well integrated, lot of
> steps to be performed to take snapshot of Gluster Volume which is
> Geo-replicated. Proposed enhancement for Geo-replication to understand
> Snapshot better and automatically handle Slave side snapshot.
>
> Proposed Solution:
> ------------------
> Take Gluster Snapshot and set Geo-replication Config
> `current-snapshot` using,
>
>     gluster volume geo-replication <MASTERVOL> <SLAVEHOST>::<SLAVEVOL> \
>         config current_snapshot <SNAPNAME>
>
> Geo-rep will automatically restart on config change and new config
> will act as switch to use Snapshot or Live Volume.
>
> Geo-rep will mount snapshot Volume in Master instead of Live
> Volume, so that Geo-rep can sync the changes from Snapshot Volume
> instead of live volume. Along with the mount Geo-rep should use the
> back end changelogs of snapshot brick instead of live brick.
>
> Geo-rep worker will update stime both in snapshot bricks and live
> bricks, this is required to prevents re-processing changelogs which
> are already processed when switched to live Changelogs.
>
> Once all the changes from Snapshot synced to slave then Geo-rep worker
> will trigger snapshot at slave side. On successful slave snapshot
> Geo-replication will automatically switches to live Volume by
> resetting current_snapshot option.
>
> Snapshot Restore:
> -----------------
> Restore both Slave and Master Volume to the same Snapshot name,
> Geo-rep should work without any further changes.
>
> Challenges:
> -----------
> - Geo-rep may not work as expected if we give old snapshot name after
>   latest snapshot name.
> - Detecting the completion of sync from Snapshot Volume(Checkpoint?)
> - Since Changelogs are generated even in Snapshot Volume, updating stime
>   on live bricks while syncing from snapshot Volume brick may cause
> problems
>   when switched back to live.
> - Finding respective snapshot brick path from live volume brick path may be
>   challenging if Bricks removed/added after taking snapshot.
>
> --
> regards
> Aravinda
>
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