How to use Media Host Override

[SteveLaw]

Hi,

We're on NB7.5.0.3, mixed Unix and Windows, master server is a Win2008 server, storage is Data Domain. 

We're testing restores of an Oracle database using RMAN. They're kind of working ok but the media server chosen for the jobs seems completely random - can be one on the local site or on the remote site. So we need to restrict which media servers are used. 

The obvious solution seems to be to add entries to the Media Host Override option. The restores were performed by one or the other of two media servers on that site (which media servers are used for the backup is controlled via the Storage Unit), so i was planning to add entries so that each on is used to restore any job they were the original backup media server for, which would look like this:

ORIGINAL BACKUP SERVER                       RESTORE SERVER

server1                                                         server1 

server2                                                         server2 

A few questions:

1) I've noticed that the Master and all the media servers have a "media host override" dialog box int he windows Admin Console. Does it make any difference which is used - does the setting take effect globally? As the host that was backed up is also a media server, I was wondering if the media host override settings for that media server might only apply to restores of that server? Or are the media host override settings global wherever they are set? 

2) Can ANY DD Bosst enabled media server be picked for a restore if this is not controlled by media host override? Even the master server was picked for one part of the restore. 

3) Can media servers restore from a storage unit even if they are not assigned to that storage unit as an available media server? It seems like any DD boost server can read any storage unit when it comes to restores...

Thanks!

[RamNagalla · Accepted solution]

not sure why, but now this tech note is not finding.. 

 http://www.symantec.com/docs/TECH87200

contect of the tech note, hopefully it will expline your queries.

DOCUMENTATION: Restores and duplications from OpenStorage backup need not use the same media server that wrote the backup.

Article ID: TECH87200

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Created: 2008-01-23

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Updated: 2011-06-02

Technical Solution for NetBackup Enterprise Server 6.0 6.5 6.5.3, NetBackup Enterprise Server 6.0 6.5 6.5.2, NetBackup Enterprise Server 6.0 6.5 6.5.1, NetBackup Enterprise Server 6.0 6.5

Issue

DOCUMENTATION: Restores and duplications from OpenStorage backup need not use the same media server that wrote the backup.

Solution

Restore and duplications from the OpenStorage disk option need not use the same media server that wrote the backup image.  This is by design as NetBackup is trying to use the media server with the least load, in accordance with Media Server Load Balancing strategy.

The media server that created the backup image is not guaranteed to be used for subsequent restores or duplications.  NetBackup will have the choice of the "best" media server and will use the load balancing logic to choose the "best" media server (e.g., a combination of number of jobs currently running on the media server, CPU usage, memory availability, et cetera).  The list from which NetBackup's Media and Device Selection (mds) and NetBackup Resource broker (nbrb) components will choose is a media server based on the storage unit for a backup. But for reads - for example, restores or the read side of a duplication - the set of media servers from which NetBackup will choose will come from the list of media servers credentialed for the storage server.

Note: The FAILOVER_RESTORE_MEDIA_SERVER and FORCE_RESTORE_MEDIA_SERVER settings in the bp.conf file as well as the Media Host Override master server Host Properties settings do not apply.  These settings will not overrule NetBackup's selection logic for OpenStorage storage units. In the NetBackup 6.5.2 Release Update, a feature was added to have preferences set up for duplication (for example), but those preferences only apply to the AdvancedDisk and SharedDisk options. 

The following steps may be taken to ensure smooth operation for restores and duplications:

1. In most cases creating this touch file on the master server will force Open storage backups to use the media server that did the backup.

   /usr/openv/netbackup/db/config/USE_BACKUP_MEDIA_SERVER_FOR_RESTORE

2. If a client's policy is configured to send backups to an OpenStorage disk, make sure that the client has SERVER entries for all the media servers which have credentials to access the associated OpenStorage storage server.  Otherwise, restores may fail with status codes 58 or status code 59 reported. 

3. If there are specific media servers which should not be used for duplications, consider deactivating them after backups. This is not a perfect solution; however, it will help to alleviate potential issues until Symantec implements a way to set up preferred media servers for restores and the read side of duplications for each storage server.
 

4. Contact Symantec Technical Support, referencing this Tech Note ID and Etrack 1483180 to obtain replacement binaries.  These binaries provide the ability to force the media server that performed the backups to be used to perform the restores. These binaries also provides additional functionality to the bprestore command with optional syntax to select the media server to perform the restore operation from the command line.  This functionality has been incorporated in to the 6.5.4 release of NetBackup.  The binaries, once installed, do not have any affect on the function of duplications.  They only affect the restore process.

 

[SteveLaw]

Hi,

I think that is out of date. It says you can only control which media server is used for restores with the touch file /usr/openv/netbackup/db/config/USE_BACKUP_MEDIA_SERVER_FOR_RESTORE. But recent threads say otherwise:

https://www-secure.symantec.com/connect/forums/restoring-using-different-media-server

It does answer my question 2) though - any media server credentialed for the storage server (e.g. any media server setup with dd boost and data domain credentials) can be chosen for the restore, unless otherwise restricted.  

[Marianne]

The TN that Nagalla posted is IMHO still valid. 

Media server selection for restore is still exactly the same for OST as described in that TN.

The post that you are referring to is for a completely different scenario where the restore media server was in fact the one who did the backup (which is the default for tape backups) but the OP wanted another media server to perform the restore.

When more than 2 media servers share the same OST STU, Media Host Override (or FORCE_RESTORE_MEDIA_SERVER) cannot be used, as the media server chosen for restore becomes a 'moving target' due to selection criteria described in TECH87200.

[SteveLaw]

Ok, thanks Marianne.

One more question: if I want to force a different media server for a specific scenario how do I do that if I have a global USE_BACKUP_MEDIA_SERVER_FOR_RESTORE command in effect?

Do I temporarily remove the touch file? 

I can see that in the NB7.5 restore client i can choose a specific media server to perform the restore. Also there's the bprestore blahblahblah -disk_media_server option. Will they force another media server if USE_BACKUP_MEDIA_SERVER_FOR_RESTORE is still in place?

[RamNagalla]

yes... you need  remove the file "USE_BACKUP_MEDIA_SERVER_FOR_RESTORE" if you wnat to force to another media server.