On Fri, May 17, 2002 at 04:08:39PM -0400, Brook Hurd wrote:
> HP C5708A DDS-3 Data Cartridge, 24GB
>
> Unfortunatly, I don't see it listed online. Anybody use this type
> before, and if so, what are the correct settings?
I use a HP DDS-3 too and I came across this definition somewhere which I use
define tapetype HP-DDS3 {
comment "Seagate STD224000N-SB Internal DDS-3 Drive"
length 11550 mbytes
filemark 0 kbytes
speed 1075 kps
}
You must bear in mind that a DDS-3 tape holds 12GB and NOT 24 GB of data,
despite what the marketing scum might like you to think. They "assume" a
compression ratio of 2:1 which I've never heard of ANYONE achieving (apart
from tape drive manufacturers in their contrived tests).
>From an informal survey on the Sun Managers mailing list, it seemed that the
compression ratios people achieve in real life vary between 1.2:1 and 1.6:1.
If you're saving already compressed data e.g. JPEG files, you'll get no
compression at all. If you intend to use amanda to compress, use the figures
above and make sure your drive doesn't try to compress (some variation on
the mt command - depends on your local system). If you're not going to
compress with amanda, you could up the length figure here. But by what ?
As you've been using an 8 GB drive (which I presume was a DDS-2 hence was
really a 4GB drive) you should have some good data to go on - what was the
most data Amanda ever put on a tape ? If it was for instance 5GB then you'd
be reasonably safe using "length 15000 mbytes".
I hope I've shed some light on what can be a confusing subject.
Kindest regards,
Niall O Broin
