HP StorageWorks DAT 72 USB

[Ashish Uttamchandani]

Hi,

The size of the data that requires backing up is 48GB, the tape is 72GB Compressed, and I imagine at least 35GB native.

When I use NTBACKUP on Windows 2003 to start my backup, after about 35GB worth of data it fails to mount, this is understandable becuase this is the native limit.

However, in NTBACKUP when I turn on /HC:ON which turns on hardware compression the same error occurs, why is this?

I have installed the HP backup app that came with the drive and I've scheduled a backup for tonight and ticked the hardware compression box so tomorrow I will see if it works with the HP app.

But, why doesn't it work with NTBACKUP? This drive supports hardware compression I presume?

[Eric de Lange (MSE)]

Hello Ashish,

Look at the data you are backing up.

If the data that you are trying to backup is already compressed (like e.g. zip, rar, mp3, most video files, etc) then the tape drive Hardware Compression will not be able to compress the data any further.

NTbackup is able to switch on the harwdare compression of the tape device. To test this you could use HP Library and Tape Tools as well.

best regards,
_Eric

[maga77]

Same problem here....

Is there a way to increase hardware compression?!?

[Eric de Lange (MSE)]

Hardware compression is either on or off. The only parameters that influence the compression results (and this the amount of data you can store on tape) is the source data itself.

If you are backing up data that is already compressed (MP3, ZIP, RAR, JPG, MPG, etc) then hardware compression can not compress that any further.

If you are backing up text files, documents etc then you will see much better compression ratio results.

Hardware compression is enabled by default however host control is allowed meaning that NTbackup and other software cabn disable it.

hth,
-Eric

[Shiju Samuel Thomas]

you could try to check if the compression of the drive is working using the LTT - Compression Test.
You can download LTT from www.hp.com/support/tapetools

One suggestion: If you are leaving H/W Compression to "ON", then Leave the S/W Compression by the Backup Application to "OFF"

[maga77]

ok... thanks... but it's very sad..
My data are various type... 50Gb of JPEG.. MDB...xls.... doc... etc..

but I can't back it up regulary with this drive.. ;-((

I'll split in 2 tapes..