HP DAT and Hardware Compression

[Bryce Farmilo]

I've seen plenty of posts in the group on this but no definitive answer.

I have three different servers all running Veritas Backup Exec v8.6 (latest patch level). They have all run previous versions and all had the same problem. I can't get Hardware Compression to work!

The device says its enabled, the jumpers are set to enable it. If I go into HP L&TT and generate a Support Tag my Tape unit proudly states that hardware compression is disabled!

If I run the compression test in L&TT it warns me that compression is disabled, I click OK to enable it and then run the test and it all looks OK. I then run a Backup Job with Veritas (with Hardware Compression enabled on the device and backup with Hardware compression set for the job) and low and behold Hardware Compression is disabled in L&TT when I generate a Support Tag after the Backup is Complete. I have not been able to fit more than 20Gig on a DDS4 tape and I know that the data I am backing up is compressible because it is mainly word documents and spreadsheets.

Please don't tell me that I shouldn't expect 40Gig from my DDS4 unit, because I don't. But I do expect more than 20 Gig and fairly so.

I have an HP DAT 40i and and HP DAT40e that both display this problem. I also have an HP DAT 24i that does the same. Interestingly I have a pair of Compaq DAT 40's that also have the same problem.

Let me just repeat, this is on multiple servers with multiple tape units. I've also seen plenty of other support requests for this so I believe this is a common problem and i'm surprised that there hasn't been resolution to it yet.

Oh yeah and just to add salt to the wound i've got a Exabyte Mammoth tape unit that is 10Gig Native that can store 17Gig on it backing up the same data i'm trying to write to the DAT40 so believe me its compressible!

Please someone help as i'm going mad with this.

Bryce Farmilo.
TelstraClear NZ

[Andi_2]

Hi,

I??ve got the same problem with a DDS3 HP 1537.
My server is running on Windows 2000 Server SP2 with ArcServe2000 SP3

[Steve W]

Something in the host (driver, O/S or backup app) is turning off hardware compression. The LTT Compression test merely *reads* the Data Compression page (0Fh) in a mode sense to determine if compression is enabled or disabled in the drive. If you (re)enable HW compression (either by the compression script, or by power cycling the drive) and it then tells you that DC is disabled after a backup job, it must be something in that job that is disabling it. It sounds like you are doing all the right things to BUExec, so check deeper into the O/S. Is there anything else talking to the drive that could be disabling DC?