cartridge tape designators

[Joe Smith]

In article <114 at brazos.Rice.edu> stiatl!meo at gatech.edu (Miles O'Neal) writes:
>X-Sun-Spots-Digest: Volume 8, Issue 70, message 1 of 15
>
>In article <4107 at kalliope.rice.edu> eli at chipcom.chipcom.com writes:
>| X-Sun-Spots-Digest: Volume 8, Issue 49, message 1 of 11
>| 
>| what is the difference between /dev/rst0 and /dev/rst8
>| and likewise between           /dev/nrst0 and /dev/nrst8
>
>The difference is the tape format. I don't remember the exact definitions,
>but basically, the 0 devices are for 45MB tape formats, and the 8 devices
>use the 60MB formats. They aren't interchangeable.
>
>Miles

I, too, would like to know the difference between rst0 and rst8 on 1/4
inch tape.  The only references I have found are on page 84 of the
"Network and System Administration" manual, part 800-1733-10, Rev A, May
1988.

rst0 = QIC-11, 9 tracks, 45 Mbytes on 450 ft, 60 Mbytes on 600 ft tape
rst8 = QIC-24, 9 tracks, 45 Mbytes on 450 ft, 60 Mbytes on 600 ft tape

This implies that the amount of storage depends only on the length of tape
and not whether you specify /dev/rst0 vs /dev/rst8.

I have been told that the tape drive always stores 512 bytes per tape
block.  There is a flag bit to say whether more data follows, a count of
valid bytes, and a checksum for the block.  Is it true that QIC-11 and
QIC-24 store the same amount of data on the tape, and just have different
standards for encoding the length and checksum?

Which format is recommended for doing dumps?  Which format should be used
for interchanging data with other systems?  In other words: when should I
use rst0 and when should I use rst8?


Joe Smith (408)922-6220 | SMTP: JMS at F74.TYMNET.COM or jms at tymix.tymnet.com
McDonnell Douglas FSCO  | UUCP: ...!{ames,pyramid}!oliveb!tymix!tardis!jms
PO Box 49019, MS-D21    | PDP-10 support: My car's license plate is "POPJ P,"
San Jose, CA 95161-9019 | narrator.device: "I didn't say that, my Amiga did!"