[5219] in linux-scsi channel archive
Re: Linux 4mm SCSI DAT Drive Settings
daemon@ATHENA.MIT.EDU (Richard Fish)
Fri Nov 27 02:43:54 1998
Date: Fri, 27 Nov 1998 00:26:17 -0700
From: Richard Fish <rjf@estinc.com>
To: Martin Gallant <martyg@wired.ml.org>, linux-scsi@vger.rutgers.edu
Martin Gallant wrote:
> Q1. By default, the system comes up with the driver configured in fixed
> block mode (512 bytes). Should I be setting the driver to variable
> block mode? (mt -f /dev/nst0 setblk 0) Will this impact
> interoperability with other drives if I ever need to move my tapes?
No and yes. We've found that for the greatest compatibility between
systems, DAT tapes should be written in fixed blocks of 512-bytes. It
is usually possible to read tapes written in other modes, but can take
some effort (basically, more 'mt' or equivalent commands).
> Q2. When I load a 60m/90m DDS-1 cartridge into the drive, "mt status"
> reports density code 0x13 (DDS-1). When I load a 120m DDS-2
> cartridge, the reported setting does NOT change. Is this normal? I
> expected the reported density to change to 0x24 (DDS-2). The reason
> I ask is I cannot get better than 2.5Gig native capacity on a DDS-2
> cartridge and I suspect the drive may be stuck in DDS-1 mode. This
> one has me stumped, I sure could use some advice on this issue.
Hmm, don't have an answer for this one off the top of my head. You
could try an 'mt setdensity' on the drive though, and see if it accepts
the new code...
> Q3. My nightly reports indicate transfer speeds on large (100's Megs,
> all fit on holding disk) level 0 dumps to be around 250kB/sec. The
> drive is rated at 350kB/Sec. Are there obvious things I can do to
> this thing to tune for a better transfer rate?
This is probably related to the density "problem" you noted above. If
you stick a DDS-1 tape in a DDS-2 drive, you get DDS-1 performance
(~175K/sec).
--
Richard Fish Enhanced Software Technologies, Inc.
Software Developer 4014 E Broadway Rd Suite 405
rjf@estinc.com Phoenix, AZ 85040
(602) 470-1115 http://www.estinc.com
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