How to stop tape backup spanning

[Erik_Spigle]

We are currently using Backup Exec for Windows Server 10.0d. Our backup device is a Sony LIB-152E (15 tape slots) which uses an AIT-3 tape device. The tapes we use are 100GB native / 260GB compressed tapes. Our current nightly backup winds up only being about 170GB. Backup Exec is setup to partition the slots in the library to 5 two slot partitions (slots 1 - 10) for our nightly backup. Each partition represents one workday of the week. The setup ultimately is meant to keep a 10 day backup tape rotation and after 10 days it recycles the first tape. Tapes are setup to not be overwritten for 7 days and therefore the two tapes in each partition are to rotate each week. This setup worked great for a few weeks and then the job just went completely berserk on us.

Now the tape backup spans across two tapes for no reason that I can see. The tapes are by all means big enough to hold the 170GB or so that we backup. We have compression set to "hardware, then software". Right now the tape that is due for the nightly backup backs up most of the stuff, then it goes to switch tapes. Overwrite protection is still on the other tape in the partition, so the job just sits there and waits until overwrite protection expires several hours later and then finishes the last few dozen GB of backup on the other tape.

Can anyone give me some clues as to why this might be happening? I'll continue to look over our job to see if it's evident. It's almost as if the backup is not really compressing things to a state where it can use all of the tape. I know in the past before we used this partitioning setup that we backed up 170.. .180... even 190GB easy to these tapes. Please help! Thank you.

[Ken_Putnam]

Any compression that you get is all that you get. The standard 2:1 ( or in your case 2.6:1) touted by manufacturers is pure marketing glitz in a non-real world enviroment. See http://support.veritas.com/docs/199542

How much data is written to the first tape berfore it jumps to the second?

I generally figure in about 1.3:1 until I have backed up a specific server serveral timesMessage was edited by:
Ken Putnam

[padmaja_rajopad]

Hi,

The toretical compression is rarely achieved by the tape hardware.

Moreover the extent of compression also depends upon the type of data being backed up. E.g.-Normal files like .txt files are more compressible as compared to the compression achieved while doing database backups.


You may also update the device drivers for the tape drive, if the device is listed in the HCL.


Symantec Backup Exec for Windows Servers (tm) 10d (10.1) Hardware Compatibility List. Includes HCL information for supported drives, libraries, virtual tape devices, fibre-channel HBAs, switches, routers/bridges, and iSCSI components. For printing purposes, the latest version of Acrobat is recommended.

http://support.veritas.com/docs/281670

For comparison purposes, you may install the latest Sony drivers as well and check whether it makes a difference.

How to use OEM drivers with Backup Exec for Windows Servers

http://support.veritas.com/docs/253974



NOTE : If we do not receive your reply within two business days, this post would be marked assumed answered and would be moved to answered questions pool.

[Erik_Spigle]

It gets to ~140GB before switching tapes. I know for fact that on this same hardware we have gotten in the 180GB range and possibly higher with a single tape. The current full backup is only ~175GB. I'll take a peek to see what compression settings are set to per the link you provided. I haven't had a chance to look again at the backup job due to some other circumstances the last few days, but I hope to soon.

Thanks for the reply.

[Erik_Spigle]

padmaja: It may be possible that the composition of our backup contents has changed in such a way to not allow as much compression, but it's hard to tell for sure at this point. I'll take a look at your suggestions and see what I can come up with. I'll go ahead and mark this as answered if there is no other information that might explain this and I'll pursue looking into the information that has been presented.

[Erik_Spigle]

Not precise answer, but some suggestions on what to look into. I'll look into the links that have been presented.