05-11-2014
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Join Date: Feb 2012
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You don't state what hardware platform you have, what the cluster software suite is, or what the backup software is.
Your post indicates that you have a good understanding of how a (generically speaking) cluster works and that any one filesystem can only be under the control of one node at a time. Having multiple nodes thinking they could write to the volume would be anarchy and a clear recipe for data corruption. It is definitely the job of the cluster software suite to ensure that that never happens. Having said that, different cluster suites can have starkly different functionality.
Similarly, backup software suites also vary in the manner of operation.
So discussing cluster backup in generic terms I would say that there are two options for implementing backups. Firstly, when node-A fails and node-B takes over (by checking orphaned filesystems and then mounting them, taking over and broadcasting the cluster name and ip address (node-C and ipaddr-C) some cluster software will also failover scheduled jobs (eg, backup). Of course, the backup device(s) need to be still available (or node-B needs to have its own tape drive, for example) for this to work. Alternatively, like all the user community who only know about node-C and ipaddr-C, the backup is run from a machine outside the cluster which "calls in" on node-C, accesses or NFS mounts the filesystem, and backs it up. Usually, this is the preferred method.
Now in this scenario the backup software has no knowledge that it is backing up a cluster volume and it should work exactly the same way as it would with a local volume, ie, if it loses communication with the volume, it will report a backup failure. Some backup software suites (eg, NetBackup) are of client/server architecture which are very intelligent and will report failures in exactly the same way they usually do.
So in summary, the fact that it is a cluster should be largely irrelevant to reporting errors in backup schedules. How the success of a backup is verified is the same as the non-cluster scenario.
Hope that helps. Feel free to continue your questions but please give us all a clue of the platform and software(s) involved.
Last edited by hicksd8; 05-11-2014 at 12:46 PM..