Tape Libraries and Drives
cancel
Showing results for 
Search instead for 
Did you mean: 

Surestore DAT24 - Compress or Not Compress?

Paul Goode
Occasional Visitor

Surestore DAT24 - Compress or Not Compress?

This is another in the saga of not compressing tapes. The drive has switches one and two set ON which as far as I can tell means compression and host control enabled. My backups don't appear to have been compressing the data although it is stored on the disks in compressed form. Looking at this drive through Tapeware indicated that compression is disabled which confirms what appears to be happening.
I downloaded the LTT software and ran the compression test. First time it said that compression was disabled, did I want to enable it (clever!). I said yes, another message flashed before my eyes connected with switches and the test passed. If I run this test again I don't get the message about compression disabled. If I go into Tapeware it stills says it's disabled. Have downloaded latest firmware (L111) but nothing's changed.
What on earth is going on?????
Are the switches working or are they back-to front?
Is the fact that data on disk is already compressed negating the hardware compression on the tape drive anyway?
1 REPLY
Eugeny Brychkov
Honored Contributor

Re: Surestore DAT24 - Compress or Not Compress?

Paul,
compressing TAPES is not a good idea :o)
Rule says that compression should be turned on only once - either in software (cleverer, but slower and consumes CPU) or hardware (faster, not so clever, but does not use CPU). Turning both on will cause data overhead.
Compression should be controlled by software. For example, ntbackup has switch '/hc:on' which turns hardware compression to on.
I guess either you need to find a menu within tapeware to turn hardware compression on or tapeware so clever not turning it on as soon as you're backing up already compressed files
Eugeny