Compression Question

[Laurie Binner]

I've recently switched my backups to BackupExec 11.d and a HP StorageWorks 460. I'm backing up a GroupWise system/post offices and the data totals just over 200GB. The job is requiring a second tape. It appears that I'm not getting any hardware compression out of the drive although I did confirm that in BExec the configuration properties of the Device shows that Compression is enabled. I realize that I won't get 2:1 compression, but based on my job, I don't think I'm getting any compression. Does anyone have any suggestions? Thanks.

[Lewis Finch]

Make sure you do not have software compression enabled, the drive has hardware compression enabled by default. Use Library and Tape Tools diagnostic to test your compression.


http://h20000.www2.hp.com/bizsupport/TechSupport/DriverDownload.jsp?pnameOID=406731&locale=en_US&taskId=135&prodSeriesId=406729&prodTypeId=12169

[Richard Bickers]

You can also use LTT to pull a support ticket straight after the backup. Make sure you disable any BE services which will lock the the driver first.

In the ticket look at:
* Drive configuration to see if the drive's DC is enabled
* Drive performance to see what compression ratio you're actually getting

I've a feeling that BE turns off hardware DC after the backup anyway so the first of these might be misleading. The second will be definitive.

The other giveaway will be that software compression is very slow.

Having said all that, you only need to compress once to get the capacity saving (doing it in software just takes longer) so the fact that you need two tapes may suggest it's down to the data not being all that compressible.

Only way to find out for sure is to make sure you're using the HW compression on the drive and *not* the software compression of BE and then pull the ticket as mentioned above. Only the drive will tell you what compression ratio you're really getting.