how does BAB know which media to use when more than 1 is available

[tordoffm]

Can anyone answer the following:

Windows 2K3 SP1 Server
BAB 11.5 SP1 installed.
Hardware - HP DL380, MSA Shelf and HP MSL 5026 Tape Library (All SCSI).

Scheme - Full backup on a weekend, Differential backups during the week (monday night through Friday night).

Backups arranged in 'Sets' - Set1 = File and Print, Set2 = Exchange, etc...

Slots 1-12 assigned to Groups appropriate to the 'Set' name. IE, Slots 1 and 2 Assigned to Group 'SET1', Slot 3 assigned to Group 'SET2', etc...

No-one to change tapes on a weekend, so on a friday only, tapes also loaded into slots 13-24 for the Full backups.
Again, slots 13-24 assigned to the relavant Group name (slot 13 and 14 = SET1, slot 15 = SET2, Slot 16 and 17 = SET3, etc...).

This means that on a friday, the Diff job can backup to 1 of two media - either the 'Differential' Tape, or the 'Full' Tape.
How do I know how BAB decides which tape to load first?
Its not slot number order - because it went wrong on one backup server this weekend, after working 100% last weekend.
Its not Alphabetical, because Backup Server 1 worked fine, and Backup Server 2 backed up Diff data to Full tape, and Full data to Diff tape - naming convention same between servers.

CA Suggest having two jobs - one for the Fulls, and one for the Diffs - each job pulling from a different Media Pools - nice idea, but I can't find a way of creating a Diff job which doesn't contain a 'Full' backup - in that case, I end up back at square one, but with an extra 'Full' backup that I don't want.

Anyone willing to lend a hand?
CA, after trying to help for 3 days, are now just sitting on this, because they don't appear to know what order their software pulls tapes in...
Also, if its random, why isn't there a massive mix between both servers of the tape that was used?

Yes, I use Media Pools, but don't trust it to work to that extend - 'Full' tapes in Save Set on a Friday, and moving (with no intervention) to Scratch Set at midnight on Friday. Media Pools are good - but not that good!

Thanks, Mark

 

[vschumpy]

It's a bit of grey area and I guess you could call it 'fuzzy logic'.

In my experience it should use the tape that was pops into the scratch set first - eg if tape 1 popped into the scratch set on 28/5 and tape 2 popped into the scratch set on 26/5, it should use tape 2 first.

I have nothing to back this evidence up - just my hunch that when BAB enumerates the list from the DB of usable tapes it will enumerate the tapes that first popped into the scratch set

As regards what should I do - that's difficult, you seem to perhaps be oversegregating the slots into groups which may be causing you added complications. As you intend to use diffs in the week and hence not use as many tapes as a full on a weekend, why not just assign the same slot ranges (together - not apart) for diff and full backups? Or maybe I'm misunderstanding you.

The other way to use different media pools for diff and full would be to utilise a GFS job - but this has its pro's and cons too.

 

[tordoffm]

Thanks vschumpy.

You might well be right thinking about it.
I formatted all of Last weeks Diff tapes for Backup Server 1, and moved the tapes to the Scratch Set before formatting and moving the Full tapes.
However, with Backup Server 2, I think I may have formatted and move the Full tapes to the Scratch Set before the Friday Diff's.
I'll give it some testing, and let you know my findings... want to put a guess at the number of worms in this can, before I open it?!!?

As for GFS - I'm not too familiar with the workings of that - having adapted what we already had, to what we use now. I'll look into GFS and see if that better suits my needs.

Thanks again.

Mark

 

[vschumpy]

hmm - difficult to say. Manually formatting tapes really isn't of any use IMO, and I couldn't really see why you'd want to do this. Manually moving tapes from save to scratch defeats the whole object of media pools and media re-use and you'll probably just end up in a mess.

All formatting does is re-write the existing tape header to say there is nothing on the tape but keeps the same name - the same as it does when it is triggered again at the start of a backup and overwrite is selected in the backup job. It should also trigger a purge of the session detail information from the db.

I can sorta see what you're trying to achieve, but to be honest most customers I have come across rely more on the barcodes than anything else to sort tapes etc. The only other times I came across this is when the customer didn't want to use as many tapes as a rotation demanded, and again to be honest, you'll waste more time and money trying to get it to work on a smaller number of tapes that it wasn't really designed to than it would have cost you to buy the additional tapes in the first place.

Good luck