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Monitoring file systems backup

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Old Unix and Linux 05-10-2014   -   Original Discussion by frhling
frhling frhling is offline
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Monitoring file systems backup

Hello,
I have some questions.
There are some File systems which are located on a SAN. There are two scenarios:
1) Some file systems are permanently mounted on certain servers
2) Others are part of a high availability cluster

In case of a cluster the needed file systems for a certain application are all visible to all cluster nodes (cluster servers) at the same time. A certain node is assigned to primarily run a certain service. Therefore it mounts the file system and provides the service as a new, virtual IP. The trick is now, that the virtual IP and virtual name can also be brought up by another cluster node in case the first one fails. This by itself is not a problem but it has turned out that this provides a problem for the backup because the backup is naturally file system oriented. From a user (or calling services) perspective the user only talks to the virtual IP and name, which never changes. He has no idea that this IP is in reality running on a physical cluster node with its own IP and name and on top of that the cluster nodes can even change.

by the default log file, I just get the machine names, mount points, full backup and incremental backups.

Now the question is how to be sure if file systems are correctly backed up?


I can think of some aproached:
1- check the list of file system and check the list of backed up files and compare to see if those FS are in back up. we pay attention to timestamp
2- the same as above but this time comparing also the size
3- check if machines in general are backed up
4- MD5 checksum

can someone give me any other idea and in general some suggestion?

Thanks
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Old Unix and Linux 05-11-2014   -   Original Discussion by frhling
hicksd8 hicksd8 is offline Forum Staff  
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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..
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