248 lines
7.1 KiB
Groff
248 lines
7.1 KiB
Groff
.\" $NetBSD: st.4,v 1.9 2003/05/01 14:11:11 wiz Exp $
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.\"
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.\" Copyright (c) 1990, 1991, 1993
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.\" The Regents of the University of California. All rights reserved.
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.\"
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.\" This code is derived from software contributed to Berkeley by
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.\" the Systems Programming Group of the University of Utah Computer
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.\" Science Department.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\" 3. All advertising materials mentioning features or use of this software
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.\" must display the following acknowledgement:
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.\" This product includes software developed by the University of
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.\" California, Berkeley and its contributors.
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.\" 4. Neither the name of the University nor the names of its contributors
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.\" may be used to endorse or promote products derived from this software
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.\" without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" from: @(#)st.4 8.2 (Berkeley) 11/30/93
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.\"
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.Dd November 30, 1993
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.Dt ST 4 hp300
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.Os
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.Sh NAME
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.Nm st
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.Nd
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.Tn CCS SCSI
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tape driver
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.Sh SYNOPSIS
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.Cd "st0 at scsi? slave ?"
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.Sh DESCRIPTION
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The
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.Nm \&st
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driver was written especially to support the Exabyte
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.Tn EXB-8200 8MM
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Cartridge
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Tape Subsystem.
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It has several extensions specific to the Exabyte,
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but should support other tape drives as long has they follow
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the
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.Tn ANSI SCSI-I
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specification.
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Besides extensive use with an Exabyte, the driver has been
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tested with an Archive
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.Tn QIC-24
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tape drive.
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The
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.Nm \&st
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tape interface provides a standard tape drive interface
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as described in
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.Xr mtio 4
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with the following exceptions:
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.Bl -enum
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.It
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Density is dependent on device type.
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Current Exabyte hardware has only one density.
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The
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.Tn EXB-8500
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drive, when released, will have a high density format of 5.6GB.
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On an Archive
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.Tn QIC-24
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drive the driver reads both
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.Tn QIC-11
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and
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.Tn QIC-24
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formats
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but writes only
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.Tn QIC-24 .
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.It
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Only the ``raw'' interface is supported.
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.El
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.Pp
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Special Exabyte Support:
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.Pp
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The
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.Dv MTIOCGET
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.Xr ioctl 2
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call on an Exabyte returns this structure:
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.Bd -literal
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struct mtget {
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short mt_type; /* type of magtape device */
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short mt_dsreg; /* sc_flags */
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short mt_erreg; /* high 8 bytes error status */
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/* low 8 bytes percentage of Rewrites
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if writing, ECC errors if reading */
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short mt_resid; /* Mbyte until end of tape */
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};
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.Ed
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.Pp
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Bit 4 in the minor device number is used
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to select long filemarks or short filemarks.
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A long filemark occupies
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2.12 MBytes of space on the tape, while a short filemark occupies 488 KBytes.
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A long filemark includes an erase gap while the short filemark does not.
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The tape can be positioned on the
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.Tn BOT
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side of a long filemark allowing
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data to be appended with a write operation.
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Since the short filemark does not contain an erase gap which would allow
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writing it is considered to be non-erasable.
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If either type of filemark is followed by blank tape,
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data may be appended on its
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.Tn EOT
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side.
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.Pp
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Bit 5 in the minor device number selects fixed block mode with a block
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size of 1K.
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Variable length records are the default if bit 5 is not set.
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.Pp
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For unit 0 here are the effects of minor device bits 2,3,4,5.
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For other units add the
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.Em unit#
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to each of the device names.
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.Bl -column norewind density filemarks -offset indent
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.Em norewind high short fixed
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.Em density filemarks block mode
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rst0
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nrst0 X
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rst8 X
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nrst8 X X
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rst16 X
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nrst16 X X
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rst24 X X
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nrst24 X X X
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rst32 X
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nrst32 X X
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rst40 X X
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nrst40 X X X
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rst48 X X
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nrst48 X X X
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rst56 X X X
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nrst56 X X X X
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.El
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.Sh SEE ALSO
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.Xr mt 1 ,
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.Xr tar 1 ,
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.Xr mtio 4
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.Rs
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.%T EXB-8200 8MM Cartridge Tape Subsystem Interface User Manual.
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.Re
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.Sh BUGS
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The
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.Tn HP
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98268
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.Tn SCSI
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controller hardware can not do odd length
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.Tn DMA
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transfers.
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If odd length
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.Tn DMA I/O
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is requested the driver will use the
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"Program Transfer Mode" of the Fujitsu
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.Tn MB87030
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chip.
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Read requests are normally even length for which a
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.Tn DMA
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transfer is used.
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If, however, the driver detects that an odd length read has happened
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(when an even length was requested) it will issue the
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.Dv EIO
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error and the last byte of the read
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data will be 0x00.
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Odd length read requests must match the size of the
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requested data block on tape.
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.Pp
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The following only applies when using long filemarks.
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Short filemarks can not be overwritten.
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.Bd -filled -offset 4n
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Due to the helical scan and the erase mechanism, there is a writing
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limitation on Exabyte drives.
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.Dq Li tar r
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or
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.Dq Li tar u
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will not work
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.Pf ( Dq Li tar c
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is ok).
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One can only start writing at
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.Bl -enum
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.It
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beginning of tape,
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.It
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on the end of what was last written,
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.It
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"front" side of a regular (long) filemark.
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.El
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.Pp
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For example, you have a tape with 3 tar files.
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If you want to save the first file, but overwrite the second two files
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with new data, on a normal 1/4" or 1/2" drive you would do:
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.Pp
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.Li "mt fsf 1; tar cf /dev/nrst0 ..."
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.Pp
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but for an Exabyte you need to do:
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.Pp
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.Li "mt fsf 1; mt bsf 1; mt weof 1; tar cf /dev/nrst0 ..."
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.Pp
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The regular long filemark consists of an erased zone 3.8" long
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(needed to begin a write).
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In this case, the first filemark is
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rewritten in place, which creates an erased zone
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.Em after
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it, clearing the
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way to write more on the tape.
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The erase head is not helical.
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.Pp
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One can position a tape to the end of what was last written by reading
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until a
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.Dq Tn BLANK CHECK
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error is returned.
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Writing can be started at this point.
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(This applies to both long and short filemarks.)
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The tape does not become positioned somewhere down the "erased" area
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as does a conventional magtape.
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One can issue multiple reads at the
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.Dq Tn BLANK CHECK
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error, but the Exabyte stays positioned at the beginning of the
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blank area, ready to accept write commands.
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File skip operations do not stop at blank tape and will run into old
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data or run to the end of the tape, so you have to be careful not to
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.Dq Li mt fsf too_many .
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.Ed
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.Pp
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Archive support gets confused if asked to moved more filemarks than there are
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on the tape.
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.Pp
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This man page needs some work.
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Some of these are not really bugs,
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just unavoidable consequences of the hardware.
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