Block Size and backup speeds

[258103645]

Hello,

I recently installed a DLT tape drive (HP Surestore VS80) to replace my Dat 20/40 drive b/c I needed the higher capacity. When I first installed the new drive, my backups took an minimum of 15 - 20 hours to complete (had about 30 gigs of data). (My DAT took about 4 hours to do the same job). After some routine testing on the drive with some downloaded diagnostics I stumbled across a document which recommended increasing the block size for DLT drives. I changed the block size on the dlt to 64k and the backups started taking about 5 - 5.5 hours to complete.

My question is that according to the documention I have seen, this drive runs at optimal performance with a block size of 128k, however BE cannot set the block size above 64k based on the drop down options. Is there a way to over ride the drop down options and set the block size to 128k. Is this even advisable?

Thanks

[Ken_Putnam]

What settings have you tried for buffers?

I wouldn't try to finagle the blocksize. About all that I would play with would be trying differrnt drivers. Have you tried manufacturer drivers or just Veritas drivers?

[258103645]

Block size : 64k
Buffer size: 64k
Buffer count: 10
Highwater count: 7

I have only tried the veritas drivers not the ones from the mfg.
Also, If this matters at all, I have an ultra 160 card controlling this tape drive (it is the only device attached to the card) and my sync rate is LOW. It is at about 20 or so, trouble is, that is the speed it autonegotiates at.

Thoughts on any of this? I can try a different driver, and increase the buffer size, if need be. The sync rate really bothered me though.

[Amruta_Purandar]

Hello,

Changing Preferred Configuration settings is not generally recommended and may have a
negative effect on your backup and system performance. Any changes should be thoroughly
tested to make sure system performance does not deteriorate before being put into general
use.
However you may refer the following documentation.
Title:
Reasons why the data throughput rate can be slower than the theoretical maximum when backing up to tape media
http://support.veritas.com/docs/231488

We hope this helps. You may also try to defragmentation of your disk.

NOTE : If we do not receive your intimation within two business days, this post would be marked ‘assumed answered’ and would be moved to the ‘answered
threads’ pool.

[Sheetal_Risbood]

As per our previous reply, marking the case as assumed answered and moving it to answered questions pool.