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Clarfication needed with how Backup Exec handles tape

Created: 16 Oct 2013 • Updated: 18 Oct 2013 | 5 comments
This issue has been solved. See solution.

Hi,

I have a few questions in regards to how Backup Exec handles tapes. My questions are as follows:

1.  Lets assume I have a job that runs Full backups during the weekends and Differential backups during weekdays. The Full backups are stored on separate tapes than the Differential backups. On weekdays, my understanding is that the tapes used for Full backups, do not need to be in the tape library  in order for the Differential backups to take place. Is this correct? If this is correct, then how does Backup Exec know which data was changed in order to make the Differential backups? Does it keep that information in the data catalogs?

2. Lets assume that I create a job and assign it a specific partition and media set. Lets also assume that I use one specific tape every time I run that job. Does Backup Exec care if next time I decide to use a different tape (a tape that was assigned to a different media set in the past) from the one I have been using? Does Backup Exec apply any association between tape barcodes, partitions and media sets? If so, how do these associations work?

3. Lets assume that I have a job that requires 3 tapes and I have a partition associated with that job that uses slots 1, 2, and 3 in my tape library. Does Backup Exec care in which of the 3 slots I put each of the 3 tapes? Do I always have to put each tape in the same slot that they were initially placed. (this questions relates to question 2, but is a bit more specific)

Thanks.

Operating Systems:

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CraigV's picture

Hi,

1. Everything would be stored in the BEDB and tape catalogs. It would know what was backed up in the FULL backup, and then check files which have changed since this backup and only back them up.

2. BE won't care if you use different tapes in a partition, as long as there are tapes available. Backup jobs are not tape specific and will not fail because TapeA is not being used instead of TapeB. If a tape is free to be used, and not in a partition, then any job that runs can use it, and the tape can therefore move between media sets. If tapes are not available in a partition, then BE will not look at another partition's tapes and use them. The job will either queue or fail.

3. No...you can mix and match the tapes in those slots. As long as they are overwritable at the time the job starts, you're good-to-go and the job should run.

Thanks!

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SOLUTION
SecurityAware's picture

Hi,

Thanks for your promt reply. On your answer to the 2nd question you say "If a tape is free to be used, and not in a partition, then any job that runs can use it, and the tape can therefore move between media sets." I am a bit confused by this. How could a tape/slot not belong to a partition? I was under the impression that all slots by default have to belong to a partition (when you configure the partitions you are forced to allocate all slots to partitions). Is this not the case? Also, when you say free to be used, you mean empty or overwrittable, correct?

Thanks.

CraigV's picture

...clarification: in an unpartitioned library. Libraries by default are not partitioned. You can split hairs around this, but they aren't. This is where any tape is free to be used if it is overwritable, and this is where a tape can move between media sets.

When partitions are configured on a tape library, and an overwritable/scratch tape is NOT available, BE will not look at another slot to use a tape there.

Thanks!

Alternative ways to access Backup Exec Technical Support:

https://www-secure.symantec.com/connect/blogs/alte...

pkh's picture

1) How BE determine which files are backed up during an incr/diff backup depends on the method that you use.  It is the same whether you backup to disk or tape.  In other words, the files to be backed up does not depend on which tape or the catalog.  For a full detail of how BE determines which file to back up, read the Admin Guide starting from page 532.

2) It is not necessary to use partitions.  I NEVER use them.  If you use partitions and do not get your OPP correct, then your job will fail even if there are overwritable tapes in the other partitions.  BE will not fetch tapes from other partitions.

If you do not use partitions, your entire library is one big partition.  You control your tape usage through the use of media sets.

3) BE does not care which tape it uses and neither should you.  BE looks for overwritable tapes using the sequence described in this document

How Backup Exec searches for overwritable media

As long as the tape is overwritable, it can be used by BE.

SOLUTION