st(7) DEVICES AND MODULES st(7)
NAME
st (mt) - SCSI tape device interface
SYNOPSIS
/dev/rmt/*{-n|-an}
DESCRIPTION
st is the SCSI tape device driver. It supports two types of
tape drives-variable length records and fixed length
records. This interface is also known as the mt (magnetic
tape) interface.
Half-inch magnetic tape and helical scan devices generally
fall into the variable record length class and quarter-inch
cartridge (QIC) devices support only fixed record lengths.
The driver determines device class at boot time.
st supports 3 standard drives: Wangtek 5099EN24 with Emulex
controller; Wangtek 5125 SCSI-36; and Archive Viper 2150S.
Examine the file /usr/include/io/stdefs.h to determine if
other devices might also be supported.
st can accommodate up to 4 tape drives at once. A logical
unit number, from 0 through 3, is assigned at boot time.
The assignment of the logical unit number depends on the
SCSI ID of the device. The lowest addressable drive is
assigned st0.
NOTE
On NWS-3700/3800 Series workstations with built-in tape
drives, the built-in drive's SCSI address is set to 5.
If you add another tape drive with a lower SCSI
address, the second drive is assigned to be st0 and the
built-in drive becomes st1. The tape device with the
lowest SCSI address is always st0.
The lower 2 bits of the device minor number are used for
specifying the device number and bits 3 and 4 are used for
specifying the recording format. The contents of the record
formats (device minor numbers) supported by st differ
depending on the type of drive. The following list gives an
example of the supported device numbers and record formats.
/dev/rmt/*[00-03] default record format of the drive
/dev/rmt/*[08-11] QIC-11/9; 1600 bpi
/dev/rmt/*[16-19] QIC-11/4; 6250 bpi
/dev/rmt/*[24-27] QIC-24/9; 3200 bpi
The driver also operates differently depending on the prefix
given to the device number:
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st(7) DEVICES AND MODULES st(7)
/dev/rmt/* rewind on close
/dev/rmt/*-n do not rewind on close
/dev/rmt/*-an do not rewind on close; auto-space to end of tape file
In auto-space mode, the drive automatically spaces forward 1
tape file on close and the head position is reset to the
beginning of the next file as long as one or more bytes of
data are actually read from the media during the time the
device is open.
ioctl
In addition to the standard drive interface described in
mtio(4), the st driver provides I/O control only for SCSI
commands included in the header file
/usr/include/io/streg.h.
Record Format of the 5099EN24 Drive
Device minor numbers 00 through 03 support QIC-24 record
format and numbers 08 through 11 support QIC-11 format.
Record Format of the 5125 Drive
The 5125 drive automatically identifies and reads QIC-120
and QIC-24 record formats. Only QIC-120 may be used for
writing. Use only minor numbers 00 through 03.
Record Format of the 2150S Drive
The lower 2 bits (bits 0 and 1) of the device minor number
are used for specifying the device number, bit 2 is used for
specifying non-rewind option, bits 3 and 4 are used for
specifying the recording format (density), and bit 5 is used
for specifying the auto-space mode. The recording format 00
supports QIC-120 record format, 01 supports QIC-150 record
format, and 10 supports QIC-24 record format. For example,
minor number 12 (binary 00001100) is used for
/dev/rmt/Q150-n which is used to deal with device 0 with
non-rewind option, QIC-150 record format, and no auto-space
mode.
FILES
/dev/rmt/* device special files
/usr/include/io/streg.h ioctl command definition
/usr/include/io/stdefs.h parameters for supported devices
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