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app cluster vs storage unit group ?

Created: 20 Oct 2013 | 2 comments
sandor.toth's picture

Hello

I have interesting question to the support community members because we configured exhange 2010 dag backup with netbackup 7.5.0.6 last week. We found very interesting things.
Exchange 2010 has 8 nodes and every nodes using netbackup media server role so I configured the app cluster right but didnt work. We run the backups on the 8 nodes all using the dag primary media server to write a backup to the tape every time.
We found one workaround and created one storage unit group and add all media servers to this group. (Media server load balance policy)

the question why not work the app cluster ? Or the storage unit group replace the app clusters ? Can I use the storage unit group if I would like to save sql in cluster environment ?

Operating Systems:

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mph999's picture

Two different things.

STU groups is a 'virtual' stu made up of individual STUs. This can run in different modes, eg. load balancing, failover.

AppCluster is the way that you 'cluster' a media server in 7.x (In 6.x you could have a real clustered media server, or an AppCluster). At 7.x, if the media servers were upgraded they stay as a real cluster, but if config from new, only an appcluster is allowed.

This TN explains, for further detail see the High Availability Guides, links are at bottom of TN.

http://www.symantec.com/docs/TECH147444

 

Regards,  Martin
 
Setting Logs in NetBackup:
http://www.symantec.com/docs/TECH75805
 
RLeon's picture

Currently, only two kinds of storages allow shared access by multiple media servers: Tape library (could be VTL) with SSO or AdvancedDisk Sharing (could use clustered file systems or CIFS/NFS mounts).
Neither of which allows Exchange GRT restores. I can see you are using tape, so I will assume that you are ok with not being able to use this feature.

 

We found one workaround and created one storage unit group and add all media servers to this group. (Media server load balance policy)

Your backup jobs may work, but the backup traffic from 7 other nodes will still travel via LAN to the "chosen" node selected by the Media server load balance policy at the start of a backup. This defeats the purpose of having either App_Cluster or a Storage Unit Group in the first place, when the intent is to have the individual nodes write to tape locally and avoid LAN traffic.

In short, you might as well not have gone through the trouble of setting up App_Cluster or STU Group (which implies configuring Media Server insteads of Client on each of the nodes), and the traffic would still go from all the nodes, through LAN, to a media server - which is how classic Exchange DAG backups should work in NetBackup.

 

the question why not work the app cluster

I discussed this topic a... erm... a little bit over here. A workaround has been suggested and I can confirmed that it worked in my lab environment. However, the method is not officially supported by Symantec on Exchange 2010 DAG, because the technote pertains to Exchange 2007 CCR.

 

Or the storage unit group replace the app clusters

No, they are for different things. The App_Cluster is to make sure that a backup of a virtual name resource to always select a media server it is currently with. With STU Groups there is no guarantee that the backup traffic will always use the media server local to the virtual name, i.e., the backup traffic may go through LAN to another media server.
With distributed database modes such as Exchange DAG/CCR or the MS SQL AlwaysON, a virtual name does not just point to a single node/media server, that is why NetBackup's App_Cluster is not suitable for such virtual name resources.

 

Can I use the storage unit group if I would like to save sql in cluster environment ?

With STU Groups, the traffic could still go through LAN to another node/media server, as explained previously.
If you are running the traditional failover cluster mode, where a MS SQL virtual name will always point to a single node/media server, then App_Cluster would do the trick nicely.
If you are running the AlwaysOn mode (which is pretty much DAG for SQL), then App_Cluster will most definitely not work, if and when NetBackup started supporting SQL AlwaysOn. (It hasn't yet.)