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1.1     ! root        1: .\" Copyright (c) 1990 The Regents of the University of California.
        !             2: .\" All rights reserved.
        !             3: .\"
        !             4: .\" This code is derived from software contributed to Berkeley by
        !             5: .\" the Systems Programming Group of the University of Utah Computer
        !             6: .\" Science Department.
        !             7: .\"
        !             8: .\" Redistribution and use in source and binary forms are permitted provided
        !             9: .\" that: (1) source distributions retain this entire copyright notice and
        !            10: .\" comment, and (2) distributions including binaries display the following
        !            11: .\" acknowledgement:  ``This product includes software developed by the
        !            12: .\" University of California, Berkeley and its contributors'' in the
        !            13: .\" documentation or other materials provided with the distribution and in
        !            14: .\" all advertising materials mentioning features or use of this software.
        !            15: .\" Neither the name of the University nor the names of its contributors may
        !            16: .\" be used to endorse or promote products derived from this software without
        !            17: .\" specific prior written permission.
        !            18: .\" THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR IMPLIED
        !            19: .\" WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF
        !            20: .\" MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
        !            21: .\"
        !            22: .\"    @(#)st.4        5.1 (Berkeley) 6/29/90
        !            23: .\"
        !            24: .TH ST 4 "June 29, 1990"
        !            25: .UC 7
        !            26: .SH NAME
        !            27: st \- CCS SCSI tape driver
        !            28: .SH SYNOPSIS
        !            29: .B "tape st0 at scsi? slave ?"
        !            30: .SH DESCRIPTION
        !            31: The
        !            32: .I st
        !            33: driver was written especially to support the Exabyte EXB-8200 8MM Cartridge 
        !            34: Tape Subsystem.  It has several extensions specific to the Exabyte,
        !            35: but should support other tape drives as long has they follow
        !            36: the ANSI SCSI-I specification.  Besides extensive use with
        !            37: an Exabyte, the driver has been tested with an
        !            38: Archive QIC-24 tape drive.
        !            39: The
        !            40: .I st
        !            41: tape interface provides a standard tape drive interface 
        !            42: as described in
        !            43: .IR mtio (4)
        !            44: with the following exceptions:
        !            45: .TP 3
        !            46: 1.
        !            47: Density is dependent on device type.  Current Exabyte hardware has
        !            48: only one density. The EXB-8500 drive, when released, will have a high
        !            49: density format of 5.6GB.
        !            50: On an Archive QIC-24 drive the driver reads both QIC-11 and QIC-24 formats
        !            51: but writes only QIC-24.
        !            52: .TP 3
        !            53: 2.
        !            54: Only the ``raw'' interface is supported.
        !            55: .PP
        !            56: Special Exabyte Support:
        !            57: 
        !            58: The MTIOCGET ioctl call on an Exabyte returns this structure:
        !            59: 
        !            60: .nf
        !            61: struct mtget {
        !            62:               short mt_type;   /* type of magtape device */
        !            63:               short mt_dsreg;  /* sc_flags */
        !            64:               short mt_erreg;  /* high 8 bytes error status */
        !            65:                                /* low  8 bytes percentage of Rewrites
        !            66:                                   if writing, ECC errors if reading */
        !            67:               short mt_resid;  /* Mbyte until end of tape */
        !            68: };
        !            69: .fi
        !            70: 
        !            71: Bit 4 in the minor device number is used
        !            72: to select long filemarks or short filemarks. A long filemark occupies
        !            73: 2.12 MBytes of space on the tape, while a short filemark occupies 488 KBytes.
        !            74: A long filemark includes an erase gap while the short filemark does not.
        !            75: The tape can be positioned on the BOT side of a long filemark allowing
        !            76: data to be appended with a write operation.  Since the short filemark does not
        !            77: contain an erase gap which would allow writing it is considered to be
        !            78: non-erasable.  If either type of filemark is followed by blank tape,
        !            79: data may be appended on its EOT side.
        !            80: 
        !            81: Bit 5 in the minor device number selects fixed block mode with a block
        !            82: size of 1K.  Variable length records are the default if bit 5 is not
        !            83: set.
        !            84: 
        !            85: For unit 0 here are the effects of minor device bits 2,3,4,5. For other
        !            86: units add the
        !            87: .I unit#
        !            88: to each of the device names.
        !            89: 
        !            90: .(b M
        !            91: .nf
        !            92:        norewind    high density    short filemarks    fixed block mode
        !            93: rst0                                                   
        !            94: nrst0      X                                           
        !            95: rst8                      X                            
        !            96: nrst8      X              X                            
        !            97: rst16                                     X        
        !            98: nrst16     X                              X        
        !            99: rst24                     X               X        
        !           100: nrst24     X              X               X        
        !           101: rst32                                                        X
        !           102: nrst32     X                                                 X
        !           103: rst40                     X                                  X
        !           104: nrst40     X              X                                  X
        !           105: rst48                                     X                  X
        !           106: nrst48     X                              X                  X
        !           107: rst56                     X               X                  X
        !           108: nrst56     X              X               X                  X
        !           109: 
        !           110: .fi
        !           111: .)b
        !           112: .SH BUGS
        !           113: 
        !           114: The HP 98268 SCSI controller hardware can not do odd length DMA
        !           115: transfers.  If odd length DMA I/O is requested the driver will use the
        !           116: "Program Transfer Mode" of the Fujitsu MB87030 chip. Read requests are
        !           117: normally even length for which a DMA transfer is used. If, however, the
        !           118: driver detects that a odd length read has happened (when a even length
        !           119: was requested) it will issue the EIO error and the last byte of the read
        !           120: data will be 0x00. Odd length read requests must match the size of the
        !           121: requested data block on tape.
        !           122: 
        !           123: The following only applies when using long filemarks. Short filemarks can
        !           124: not be overwritten.
        !           125: 
        !           126: .(q
        !           127: .in +4
        !           128: Due to the helical scan and the erase mechanism, there is a writing
        !           129: limitation on Exabyte drives. "tar r" or "tar u" will not work ("tar c"
        !           130: is ok).  One can only start writing at  1) beginning of tape, 2) on the
        !           131: end of what was last written, 3) "front" side of a regular (long) filemark.
        !           132: Say you have a tape with 3 tar files on it, want to save the first
        !           133: file, and want to begin writing over the 2nd file.
        !           134: 
        !           135: On a normal 1/4" or 1/2" drive you would do:
        !           136: 
        !           137: "mt fsf 1; tar cf /dev/nrst0 ..."
        !           138: 
        !           139: but for an Exabyte you need to do:
        !           140: 
        !           141: "mt fsf 1; mt bsf 1; mt weof 1; tar cf /dev/nrst0 ..."
        !           142: 
        !           143: The regular long filemark consists of an erased zone 3.8" long
        !           144: (needed to begin a write).  In this case, the first filemark is
        !           145: rewritten in place, which creates an erased zone AFTER it, clearing the
        !           146: way to write more on the tape.  The erase head is not helical.
        !           147: 
        !           148: One can position a tape to the end of what was last written by reading
        !           149: until a "BLANK CHECK" error is returned.  Writing can be started at this
        !           150: point.  (This applies to both long and short filemarks.)  The tape does
        !           151: not become positioned somewhere down the "erased" area as does a
        !           152: conventional magtape.  One can issue multiple reads at the "BLANK
        !           153: CHECK" error, but the Exabyte stays positioned at the beginning of the
        !           154: blank area, ready to accept write commands.  File skip operations do
        !           155: not stop at blank tape and will run into old data or run to the end of
        !           156: the tape, so you have to be careful not to "mt fsf too_many".
        !           157: .in -4
        !           158: .q)
        !           159: 
        !           160: Archive support gets confused if asked to moved more filemarks than there are
        !           161: on the tape.
        !           162: 
        !           163: This man page needs some work.  Some of these are not really bugs,
        !           164: just unavoidable consequences of the hardware.
        !           165: .SH "SEE ALSO"
        !           166: mt(1),
        !           167: tar(1),
        !           168: mtio(4),
        !           169: 
        !           170: .I "EXB-8200 8MM Cartridge Tape Subsystem Interface User Manual."

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