Re: SCSI Tape driver

Michael Stone (mstone@itri.loyola.edu)
Thu, 18 Sep 1997 11:09:55 -0400

Quoting Richard B. Johnson (root@chaos.analogic.com):
> The SCSI tape devices have a major and minor number. If you want the tape
> to stay where it was after using 'mt', you use the device with the minor
> number's high-bit set.
>
> /dev/st0 9, 0
> /dev/st1 9, 1
> /dev/st3 9, 128
> /dev/st4 9, 129
>
> In this case /dev/st0 and /dev/st3 refer to the exact same drive. If
> you are using commands that require the state of the tape-drive to
> remain unchanged, you use /dev/st3. If you want the tape to rewind or,
> if supported unload, you use /dev/st0.

Hmm. In my copy of devices.txt, it says this:

9 char SCSI tape devices
0 = /dev/st0 First SCSI tape, mode 0
1 = /dev/st1 Second SCSI tape, mode 0
...
32 = /dev/st0l First SCSI tape, mode 1
33 = /dev/st1l Second SCSI tape, mode 1
...
64 = /dev/st0m First SCSI tape, mode 2
65 = /dev/st1m Second SCSI tape, mode 2
...
96 = /dev/st0a First SCSI tape, mode 3
97 = /dev/st1a Second SCSI tape, mode 3
...
128 = /dev/nst0 First SCSI tape, mode 0, no rewind
129 = /dev/nst1 Second SCSI tape, mode 0, no rewind
...
160 = /dev/nst0l First SCSI tape, mode 1, no rewind
161 = /dev/nst1l Second SCSI tape, mode 1, no rewind
...
192 = /dev/nst0m First SCSI tape, mode 2, no rewind
193 = /dev/nst1m Second SCSI tape, mode 2, no rewind
...
224 = /dev/nst0a First SCSI tape, mode 3, no rewind
225 = /dev/nst1a Second SCSI tape, mode 3, no rewind

Which would seem to imply that the prefix 'n' indicates a device
which doesn't automatically rewind. The method you suggested would
cause serious problems for someone who wanted to use multiple tape
drives.

As long as I'm sending stuff off to the list, can someone answer another
question: What do the postfixes l, m, and a mean? (IOW, what are the
4 modes for tapes?)

-- 
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