Two Jobs - Different Results

[JJ1000]

We have two backup jobs setup to run, one to run Monday thru Thursday, and the other to run on Fridays. Also, we are using an 8 tape HP Ultirum deck.

Here the issue:

Our Monday - Thursday backup will backup a total of nearly 700GB across 5 tapes, but our Friday backup only gets to about 617GB before it asks for another tape.

Although our Friday job is set to backup slightly more, it puzzles me why the Friday job doesn't get to closer to 700GB before it asks for another tape.

Any insight would be greatly appreciated.

[Ken_Putnam]

Are you using the same select list for both jobs - That is, are you backing up the same data?

Compression can vary greatly depending on the data type and the data itself. See http://seer.support.veritas.com/docs/199542.htm

[JJ1000]

In addition to backing up the same data that is backup up on Monday thru Thursday, the Friday backup also backs up our exchange data.

While this could make a slight difference, I don't see how it could cause that big of a discrpency.

[Dave_Bunye]

An Exchange database could be a substantial difference in size, depending on how many users and how much activity. Try seperating the Friday backup into two jobs, one which backs up the regular items, and one which backs up Exchange. See if both complete individually, and if the Exchange job asks for a new tape, at least you will see how big it is and be able to plan accordingly.

[JJ1000]

THe thing that puzzles me is:

JOB A (M-TH) uses nearly 700GB to finish, but finishes.
JOB B (Friday) asks for a new tape at 617GB.

Shouldn't JOB B be asking me for a new tape at nearly 700GB, not 617GB?

[Ben_McBeen]

Does the "slightly more" data come at the beginning or end of your backup job. That makes all the difference. The compression ratio of different types of data is not static, and I would guess that what you are adding does not compress well.

[JJ1000]

Even if it weren't compressing as well, wouldn't it still use the roughly 700GB that the other job is using, but just require more space in addition?

Its almost as if it's not fully utilizing the tape space on the Friday backup jobs. I would think it should at least use up the 700GB that it is using for the M-TH backups. Instead, it quits at 617GB.

Same tapes, but one job utilizes nearly all 700GB, while the other asks for another tape at 617GB.

[Ben_McBeen]

The 700 value you are giving is not a static value, and does not represent what data size actually going to tape. Go to your media section, and look at the media details for the tapes from each job. I'm sure you will see that the actual data written to tape will be different from the actual amount backed up. The ratio of this difference is the compression ratio you see in the statistics area.

The reason for this has to do with the way backup exec calculates data size. It calculates based on data READ not written.

The only easy way to eliminate this confusion is having a two stage backup. The first backs up to disk with compression, the second to tape with no compression. This scenario will always show tapes as having the same capacity from day to day.

[JJ1000]

That makes sense - thanks for taking the time to explain it to me. Guess we'll have to expand to another tape on Fridays or change the backup jobs.