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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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