On Wed, 2 Dec 1998, Jon Lewis wrote:
> I just had someone add a DDS2 DAT to a remote server, and though they
> claim it has a DDS2 tape in it, the drive says it's using DDS1. To see if
> it was reporting bogus info, I made a file of 1mb from /dev/urandom, and
> sent 3139 copies of that file to /dev/nst0 before it told me it was out of
> space. That's better compression than I expeced from /dev/urandom, but
> seems to confirm I'm not getting 4gb native. The drive ids as:
>
> Host: scsi0 Channel: 00 Id: 01 Lun: 00
> Vendor: SONY Model: SDT-7000 Rev: 0300
> Type: Sequential-Access ANSI SCSI revision: 02
> # mt -f /dev/nst0 status
> SCSI 2 tape drive:
> File number=3139, block number=1, partition=0.
> Tape block size 0 bytes. Density code 0x13 (DDS (61000 bpi)).
The DAT drives select the density entirely based on the tape that is in
the drive. Some drives (like my HP C1533A) change the density code
reported to the driver base on the tape, some don't (Sony drives are known
not to change the code). Some drives allow you to try to change the
density (but this does not have any effect), some refuse to do that (it
seems that your drive behaves in this way).
If you can put 3139 1 MB files of random data to the tape with
compression, the drive probably uses DDS-2 density. If you try the same
without compression, you probably can fit more files to the tape :-)
Kai
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