Hi,
I'm not the biggest rbd-mirror expert.
As understand it, if you use one-way mirroring you can failover to the
remote site, continue to work there but there's no failover back to
primary site. You would need to stop client IO on DR, demote the image
and then import the remote images back to primary site. Once
everything is good you can promote the image on primary again. The
rbd-mirror will then most likely be in a split-brain situation, which
can be resolved by resyncing images from primary again. You can't do a
resync on primary site because there's no rbd-mirror daemon running.
Having two-way mirroring could help, I believe. Let's say you lose the
primary site, you can (force) promote images on the remote site,
continue working. Once the primary site is back up (but not primary
yet), you can do the image resync from the remote (currently primary)
site (because there's a rbd-mirror daemon running on the primary site
as well). Once the primary site has all images promoted, you'll
probably have to resync on the remote site again to get out of the
split-brain. But at least you won't need to export/import images.
But you'll need to test this properly to find out if your requirements
are met.
Regards,
Eugen
Zitat von V A Prabha <prabhav@xxxxxxx>:
Dear Eugen,
We have a scenario of DC and DR replication, and planned to explore RBD
mirroring with both Journaling and Snapshot mechanism.
I have a 5 TB storage at Primary DC and 5 TB storage at DR site with
2 different
ceph clusters configured.
Please clarify the following queries
1. With One way mirroring, the failover works fine in both journaling and
snapshot mechanism and we are able to promote the workload from DR site. How
does Failback work? We wanted to move the contents from DR to DC but
it fails.
In journaling mechanism, it deletes the entire volume and recreates it afresh
which does not solve our problem.
2. How does incremental replication work from DR to DC?
3. Does Two-way mirroring help this situation. According to me, in
this method,
it is for 2 different clouds with 2 different storages and
replicating both the
clouds workloads? Does Failback work in this scenario ?
Please help us / guide us to deploy this solution
Regards
V.A.Prabha
Thanks & Regards,
Ms V A Prabha / श्रीमती प्रभा वी ए
Joint Director / संयुक्त निदेशक
Centre for Development of Advanced Computing(C-DAC) / प्रगत संगणन विकास
केन्द्र(सी-डैक)
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