cartridge tape designators
andrew yeomans
cel!ajy at uunet.uu.net
Tue Aug 22 23:35:29 AEST 1989
I prepared the following fact sheet on both the 9-track tape unit which we
use, and the Sun cartridges.
The info on the 9-track tape drive was obtained from mtio(4), xt(4S) and a
fair bit of experimentation. If you are lucky, it may also be true for
your own mag tape drives.
The info on the cartridge tapes comes from mtio(4), st(S) and several
contributors to Sun-Spots [sorry, I've forgotten who sent what]. The
bottom line is that there is very little to choose between rst0 and rst8
for the amount of data you get on the tape. However, whichever you choose,
you won't be able to read the tape back on some other machines! Sun-Spots
also explained the problems of booting SunOS installation tapes - If I
remember correctly, the boot proms in the earlier Sun 3 workstations could
only read QIC-11 format. Sun in their wisdom supplied SunOS 4 in QIC-24
format, necessitating users to upgrade their boot proms.
___ ___ ___
Andrew Yeomans PSTN: 0442 230000 ext 3371 |XXX| |XXX| | |
Crosfield Electronics Ltd INTL: +44 442 230000 |XXX| |XXX| |___|
Three Cherry Trees Lane Fax: 0442 232301 ___ ___ ___
Hemel Hempstead UUCP: ajy at cel.uucp |XXX| | | | |
Hertfordshire or mcvax!cel!ajy at uunet.uu.net |XXX| |___| |___|
HP2 7RH ___ ___ ___
England .. all opinions are my own, etc. |XXX| |XXX| | |
'The network is the bottleneck' |XXX| |XXX| |___|
-------------------------- cut here -------------------------------------
Magnetic tape devices
---------------------
xt - Xylogics 472 1/2 inch tape controller
------------------------------------------
Device name Maj Min Rewind on close Density Block size
Fixed block size mode:
/dev/mt0 8 0 Rewinding 1600 bpi 2048 bytes
/dev/nmt0 =/dev/mt4 8 4 Non-rewinding 1600 bpi 2048 bytes
/dev/mt8 8 8 Rewinding 6250 bpi 2048 bytes
/dev/nmt8 =/dev/mt12 8 12 Non-rewinding 6250 bpi 2048 bytes
Variable block size (raw) mode:
/dev/rmt0 30 0 Rewinding 1600 bpi Variable
/dev/nrmt0 =/dev/rmt4 30 4 Non-rewinding 1600 bpi Variable
/dev/rmt8 30 8 Rewinding 6250 bpi Variable
/dev/nrmt8 =/dev/rmt12 30 12 Non-rewinding 6250 bpi Variable
For compatibility reasons, the non-rewinding devices can be accessed by
either of the two names given.
'tar' and 'dump' default to using /dev/rmt8 (rewinding).
'mt' defaults to using /dev/rmt12 (non-rewinding).
The tape density may only be changed when writing if the tape is at the
load point, and if the drive is set to 'host-selectable density'.
The actual recorded tape density is used when reading or when writing
other than at load point, and any attempts to set it (on the front panel
or by device name) are ignored. The density status lights show the
selected density, not the actual recorded tape density.
st - SCSI 1/4 inch cartridge tape
---------------------------------
Device name Maj Min Rewind on close Format Block size
/dev/rst0 18 0 Rewinding QIC-11 512*n bytes
/dev/nrst0 18 4 Non-rewinding QIC-11 512*n bytes
/dev/rst8 18 8 Rewinding QIC-24 512*n bytes
/dev/nrst8 18 12 Non-rewinding QIC-24 512*n bytes
There are two parameters to consider with 1/4 inch cartridge tapes.
One is the number of tracks (4 or 9), the other is the encoding format
(QIC-11 or QIC-24). QIC-11 uses 1 byte block numbers, while QIC-24 uses
3 byte block numbers. QIC-11 has fractionally greater tape density,
while QIC-24 is more robust.
Tapes written by a 4-track drive can be read on a 9-track drive.
Tapes written by a 9-track drive may sometimes be read on a 4-track
drive, but with no guarantee of success.
Old Sun-2 machines can only write 4-track QIC-11 tapes.
Newer Sun-2 machines can only write 9-track QIC-11 tapes.
Sun-3 machines can only write 9-track QIC-11 or 9-track QIC-24 tapes.
Andrew J. V. Yeomans
14th June 1989
More information about the Comp.sys.sun
mailing list