Re: Two clusters on same hosts - mirroring

[David Turner <drakonstein@xxxxxxxxx>]

I'm sure you can set up 2 different clusters in the same machine and configure them to mirror RBD's between them.  I do not believe that this has any usefulness other than learning the commands and testing scripts.  No benchmarking will be useful at all and any problems you run into might just be because of your configuration as opposed to the actual mirroring.  You probably won't find many people that have done this method to be able to troubleshoot problems with it.  You are intending to use mirroring between multiple locations and not just in the same building/data center, correct?  If you are intending to use 2 clusters in the same building (or on the same hardware), then mirroring will gain you nothing and just configuring more replicas will give you the same resiliency.

RBDs have nothing to do with CephFS.  CephFS has no visibility of what RBDs you are using for VMs so you can't use it to back up RBD data to an external source.  Ceph's backup solution for RBDs is snapshotting the RBD and being able to clone the snapshot or restore the RBD to a snapshot.  This doesn't remove the cluster as a whole from being the single point where your data is, but it is an actual backup of the VM data.  I haven't heard of anyone backing up RBDs to tape backups before.  My only guess as to how that would be done would be to create a snapshot of the RBD, cloning the snapshot, mapping the cloned RBD to a machine that you then back up to tape.

On Mon, Aug 14, 2017 at 4:09 PM Oscar Segarra <oscar.segarra@xxxxxxxxx> wrote:

Hi, 

Anybody has been able to work with mirroring? 

does has any sense the scenario I'm proposing?

Thanks a lot.

2017-08-08 20:05 GMT+02:00 Oscar Segarra <oscar.segarra@xxxxxxxxx>:

Hi, 

I'd like to use the mirroring feature 

http://docs.ceph.com/docs/master/rbd/rbd-mirroring/

In my environment I have just one host (at the moment for testing purposes before production deployment).

I want to dispose:

/dev/sdb for standard operatoin

/dev/sdc for mirror 

Of course, I'd like to create two clusters, each cluster with a pool "mypool" and enable mirror.

The final idea is using CephFS for exporting to tape my VMs in consistent state without affecting production OSD /dev/sdb.

http://docs.ceph.com/docs/master/cephfs/createfs/

Anybody has tried something similar? can anybody explain his experience?

Thanks a lot.

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