Topic: HP surestore dat24 actual capacity?

[Sam]

Hi,
A quick question, I tested dat24 on windows backup, it gave me 10.4 GB on dds3 tapes (12/24), tried another tape drive same model on windows/linux/sme, it worked upto the same capacity 10.4GB, and then full.Did anyone see this, any thoughts??? how to make it work for 24gb storage. The backup capacity is not changed by compression on/off.
Thanks

[TimH]

The figure tape drive manufactures quote is always based on a certain level of data compression - usually 2 or 3 times the native capacity.  The level you'll get depends on how compressible your data is (assuming you have hardware compression enabled on the drive).

Either your data is already heavily compressed - i.e. zipped/tarred/cab files etc, or your not getting h/w compression on the drive.

In general I see about 2:1 compression for general file server type data (office docs etc).

[Michael Doerner]

Hi Sam,

apparently there is no hardware compression for DAT (and other) SCSI tape drives in current versions of SME server.

We have 1 site with an older HP DAT drive (4/8 GB) where hardware compression was working fine with an older SME version (as far as I remember, it was SME 5.0) but since we upgraded to SME 5.1.2, flexbackup always stops at 3.9 GB.
The 4 GB limitation also happens when testing with a 4/8 GB SLR (Tandberg) drive.

I think it's not an SME issue since SME is based on Redhat.
The "mt" command version & features have changed over the time and the current mt seems to have less options to enable hardware compression (strange to me).

I would be happy if someone can prove me wrong ...

Regards,
Michal Doerner