Failover from tape to DSSU?

[IanB]

We have NBu Enterprise 6.5.6 - SAN storage for DSSUs (basic disk), and 2 tape libraries (each 2 LTO4 drives).

Backup to disk and duplication to DSSUs - all works great.  Indeed for Exchange mailservers (a few big databases), the speed is so good that I have changed the method and started backing up direct to both tape libraries.  This saves >1TB of DSSU space and means that the images get to tape quicker.

But after a weekend full backup (200 policies, 16TB backed up), on Monday evening the tape libraries are still busy duplicating images, so no free tape drives and the Exchange backups have been failing (backup window eventually closed).  Rather than extending the window (I know that works), I added a DSSU as a 3rd storage unit in the DualTapes STU, and set them as Prioritised.  Because I'd like to get the backup done straightaway, on tape as first choice, but if not possible then to disk.  But it hasn't been picking up the DSSU (no evidence that it even tries), and it still fails when the window closes.

Any ideas, please?

TIA

Ian

[Marianne]

I suppose your last paragraph means that you have added DSU to STUG with Prioritzed selection?

Looking at Admin Guide I, it seems that this is the best possible selection.

Prioritized
NetBackup chooses the first storage unit in the list that is not busy, down, or out of media. Also, the storage unit must not have reached the maximum concurrent jobs setting. When one of the specified conditions occurs, the next storage unit in the list is examined until NetBackup finds an available storage unit. If one is not available or if one does not have enough available space, the job fails and is not queued. (Default.)

Failover
NetBackup chooses the first storage unit in the list that is not down, out of media, or full. If a storage unit is only busy, the policy waits to write to it. The other storage units are used as failovers.
NetBackup queues a job to wait for the first storage unit if the maximum concurrent jobs setting is reached.

What you are seeing looks like Failover is applied, rather than Prioritized.

Being on 6.x, I would personally not spend too much energy on trying to troubleshoot this, since 6.x will be EOSL in October (yes, I know I sound like a 'stuck record').

My recommendation is to upgrade to 7.1, preferrably 7.5 and see if that makes a difference. If not, Symantec Support should be able to troubleshoot resource selection for you.

I do not see any 'quick solution' here... sorry...

Hopefully other experts will come along soon with ideas that will help right away....

[mph999]

Hi Ian,

Tape 'can' be so fast now, it can out run disk.

Anyway to your issue - In the back of my mind I believe it is not recommend to mix disk/  tape in a STU  group I'm not sure if this is documented anywhere, but checking a few previous cases I see that colleagues who are very experienced have made this recommendation. I have just checked with a colleague in the US and this was his view also.

I'm thinking that nbrbutil -dump may show some reason for the selection that is made, or more accurately, why the disk stu is not being selected.

Just as a test, would you be able to try round-robin selection.

Regards,

Martin