Arcserve 2k compression

[epierson]

Hi, im using arcserve 2k on a dell poweredge 2650 running windows 2000. I'm using a Spectra 2k which uses 2 Sony SDX-500C tape drives that support hardware compression.

I have read many if not all the topics related to this issue and i still can not get compression to work. I've checked the device and both tape drives show hardware compression on, i've also used a the testing software from specralogic to test the tape backup unit and it has compressed test data successfully.
I've attempted backing up the server locally, the raid attatched to the server, and a raid attatched to sun we also have running here. i get zero compression on all backups, i'm using 50/100 AIT2 tapes and once they get to exactly 50 a new take picks up.

This has been driving me up a wall for 2 weeks now, i can not get any compression and i know it was working before when the tape back up was attached to an older server running windows NT. I've tried everything listed in the Faq as far as compression is concerned the drive only supports hardware compression i can not turn it off to try using software compression.

I would appreciate any help i could get thank you.

-Eric Pierson

 

[epierson]

Any ideas on this, from anyone? I'll even take a toss it out the window. Something as a starting point would be good too, so i can go at it from a different direction maybe.

 

[davidmichel]

Check the type of data.

Compressed data can not be compressed. So for example if you backed up 50gb of jpg, mp3, zip, or any compressed data it will fill up the tape.

The 50/100 does not mean 50gb native and 100gb with compression. It means 50gb native and the guys in Marketing said to use 100gb for compression. In real life it totally depends on the data. So as mentioned if 50gb of compressed data is backed up there will be no compression.

Here is another thing to think about. SoftWrite errors = bad spots on tape. The drive tried to write data but failed so it moved the tape to the next block and retried. It keeps doing this until the data is written correctly or until a preset threshold is exceeded and it becomes a HardWrite or Media error. So the more SoftWrite errors the more space on tape is wasted.