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1 perry 1 ST
2 !!!ST
3 NAME
4 SYNOPSIS
5 DESCRIPTION
6 DATA TRANSFER
7 IOCTLS
8 RETURN VALUE
9 FILES
10 AUTHOR
11 SEE ALSO
12 NOTES
13 COPYRIGHT
14 ----
15 !!NAME
16
17
18 st - SCSI tape device
19 !!SYNOPSIS
20
21
22 __#include
23 __ ''fd''__, int__ ''request'' __[[, (void *)__''arg3''__])
24 int ioctl(int__ ''fd''__, MTIOCTOP, (struct mtop *)__''mt_cmd''__)
25 int ioctl(int__ ''fd''__, MTIOCGET, (struct mtget *)__''mt_status''__)
26 int ioctl(int__ ''fd''__, MTIOCPOS, (struct mtpos *)__''mt_pos''__)
27 __
28 !!DESCRIPTION
29
30
31 The __st__ driver provides the interface to a variety of
32 SCSI tape devices. Currently, the driver takes control of
33 all detected devices of type ``sequential-access.'' The
34 __st__ driver uses major device number 9.
35
36
37 Each device uses eight minor device numbers. The lower-most
38 five bits in the minor numbers are assigned sequentially in
39 the order of detection. The minor numbers can be grouped
40 into two sets of four numbers: the principal (auto-rewind)
41 minor device numbers, ''n'', and a ``no-rewind'' device
42 numbers, (''n''+ 128). Devices opened using the principal
43 device number will be sent a REWIND command
44 when they are closed. Devices opened using the ``no-rewind''
45 device number will not. (Note that using an auto-rewind
46 device for positioning the tape with, for instance, mt does
47 not lead to the desired result: the tape is rewound after
48 the mt command and the next command starts from the
49 beginning of the tape).
50
51
52 Within each group, four minor numbers are available to
53 define devices with different characteristics (block size,
54 compression, density, etc.) When the system starts up, only
55 the first device is available. The other three are activated
56 when the default characteristics are defined (see below).
57 (By changing compile-time constants, it is possible to
58 change the balance between the maximum number of tape drives
59 and the number of minor numbers for each drive. The default
60 allocation allows control of 32 tape drives. For instance,
61 it is possible to control up to 64 tape drives with two
62 minor numbers for different options.)
63
64
65 Devices are typically created by:
66
67
68 mknod -m 666 /dev/st0 c 9 0
69 mknod -m 666 /dev/st0l c 9 32
70 mknod -m 666 /dev/st0m c 9 64
71 mknod -m 666 /dev/st0a c 9 96
72 mknod -m 666 /dev/nst0 c 9 128
73 mknod -m 666 /dev/nst0l c 9 160
74 mknod -m 666 /dev/nst0m c 9 192
75 mknod -m 666 /dev/nst0a c 9 224
76
77
78 There is no corresponding block device.
79
80
81 The driver uses an internal buffer that has to be large
82 enough to hold at least one tape block. In kernels before
83 2.1.121, the buffer is allocated as one contiguous block.
84 This limits the block size to the largest contiguous block
85 of memory the kernel allocator can provide. The limit is
86 currently 128 kB for the 32-bit architectures and 256 kB for
87 the 64-bit architectures. In newer kernels the driver
88 allocates the buffer in several parts if necessary. By
89 default, the maximum number of parts is 16. This means that
90 the maximum block size is very large (2 MB if allocation of
91 16 blocks of 128 kB succeeds).
92
93
94 The driver's internal buffer size is determined by a
95 compile-time constant which can be overridden with a kernel
96 startup option. In addition to this, the driver tries to
97 allocate a larger temporary buffer at run-time if necessary.
98 However, run-time allocation of large contiguous blocks of
99 memory may fail and it is advisable not to rely too much on
100 dynamic buffer allocation with kernels older than 2.1.121
101 (this applies also to demand-loading the driver with kerneld
102 or kmod).
103
104
105 The driver does not specifically support any tape drive
106 brand or model. After system start-up the tape device
107 options are defined by the drive firmware. For example, if
108 the drive firmware selects fixed block mode, the tape device
109 uses fixed block mode. The options can be changed with
110 explicit __ioctl()__ calls and remain in effect when the
111 device is closed and reopened. Setting the options affects
112 both the auto-rewind and the non-rewind device.
113
114
115 Different options can be specified for the different devices
116 within the subgroup of four. The options take effect when
117 the device is opened. For example, the system administrator
118 can define one device that writes in fixed block mode with a
119 certain block size, and one which writes in variable block
120 mode (if the drive supports both modes).
121
122
123 The driver supports __tape partitions__ if they are
124 supported by the drive. (Note that the tape partitions have
125 nothing to do with disk partitions. A partitioned tape can
126 be seen as several logical tapes within one medium.)
127 Partition support has to be enabled with an ioctl. The tape
128 location is preserved within each partition across partition
129 changes. The partition used for subsequent tape operations
130 is selected with an ioctl. The partition switch is executed
131 together with the next tape operation in order to avoid
132 unnecessary tape movement. The maximum number of partitions
133 on a tape is defined by a compile-time constant (originally
134 four). The driver contains an ioctl that can format a tape
135 with either one or two partitions.
136
137
138 Device __/dev/tape__ is usually created as a hard or soft
139 link to the default tape device on the system.
140 !!DATA TRANSFER
141
142
143 The driver supports operation in both fixed block mode and
144 variable block mode (if supported by the drive). In fixed
145 block mode the drive writes blocks of the specified size and
146 the block size is not dependent on the byte counts of the
147 write system calls. In variable block mode one tape block is
148 written for each write call and the byte count determines
149 the size of the corresponding tape block. Note that the
150 blocks on the tape do don't contain any information about
151 the writing mode: when reading, the only important thing is
152 to use commands that accept the block sizes on the
153 tape.
154
155
156 In variable block mode the read byte count does not have to
157 match the tape block size exactly. If the byte count is
158 larger than the next block on tape, the driver returns the
159 data and the function returns the actual block size. If the
160 block size is larger than the byte count, the requested
161 amount of data from the start of the block is returned and
162 the rest of the block is discarded.
163
164
165 In fixed block mode the read byte counts can be arbitrary if
166 buffering is enabled, or a multiple of the tape block size
167 if buffering is disabled. Kernels before 2.1.121 allow
168 writes with arbitrary byte count if buffering is enabled. In
169 all other cases (kernel before 2.1.121 with buffering
170 disabled or newer kernel) the write byte count must be a
171 multiple of the tape block size.
172
173
174 A filemark is automatically written to tape if the last tape
175 operation before close was a write.
176
177
178 When a filemark is encountered while reading, the following
179 happens. If there are data remaining in the buffer when the
180 filemark is found, the buffered data is returned. The next
181 read returns zero bytes. The following read returns data
182 from the next file. The end of recorded data is signaled by
183 returning zero bytes for two consecutive read calls. The
184 third read returns an error.
185 !!IOCTLS
186
187
188 The driver supports three ioctl requests. Requests not
189 recognized by the __st__ driver are passed to the
190 __SCSI__ driver. The definitions below are from
191 __/usr/include/linux/mtio.h__:
192
193
194 __MTIOCTOP - Perform a tape
195 operation__
196
197
198 This request takes an argument of type __(struct mtop
199 *)__. Not all drives support all operations. The driver
200 returns an EIO error if the drive rejects an
201 operation.
202
203
204 /* Structure for MTIOCTOP - mag tape op command: */
205 struct mtop {
206 short mt_op; /* operations defined below */
207 int mt_count; /* how many of them */
208 };
209 Magnetic Tape operations for normal tape use:
210
211
212 MTBSF Backward space over __mt_count__
213 filemarks.
214
215
216 MTBSFM Backward space over __mt_count__ filemarks.
217 Reposition the tape to the EOT side of the last
218 filemark.
219
220
221 MTBSR Backward space over __mt_count__ records (tape
222 blocks).
223
224
225 MTBSS Backward space over __mt_count__
226 setmarks.
227
228
229 MTCOMPRESSION
230
231
232 Enable compression of tape data within the drive if
233 __mt_count__ is non-zero and disable compression if
234 __mt_count__ is zero. This command uses the MODE page 15
235 supported by most DATs.
236
237
238 MTEOM Go to the end of the recorded media (for appending
239 files).
240
241
242 MTERASE
243
244
245 Erase tape.
246
247
248 MTFSF Forward space over __mt_count__
249 filemarks.
250
251
252 MTFSFM Forward space over __mt_count__ filemarks.
253 Reposition the tape to the BOT side of the last
254 filemark.
255
256
257 MTFSR Forward space over __mt_count__ records (tape
258 blocks).
259
260
261 MTFSS Forward space over __mt_count__
262 setmarks.
263
264
265 MTLOAD Execute the SCSI load command. A special case is
266 available for some HP autoloaders. If __mt_count__ is the
267 constant MT_ST_HPLOADER_OFFSET plus a number, the number is
268 sent to the drive to control the autoloader.
269
270
271 MTLOCK Lock the tape drive door.
272
273
274 MTMKPART
275
276
277 Format the tape into one or two partitions. If
278 __mt_count__ is non-zero, it gives the size of the first
279 partition and the second partition contains the rest of the
280 tape. If __mt_count__ is zero, the tape is formatted into
281 one partition. This command is not allowed for a drive
282 unless the partition support is enabled for the drive (see
283 MT_ST_CAN_PARTITIONS below).
284
285
286 MTNOP No op - flushes the driver's buffer as a side effect.
287 Should be used before reading status with
288 MTIOCGET .
289
290
291 MTOFFL Rewind and put the drive off line.
292
293
294 MTRESET
295
296
297 Reset drive.
298
299
300 MTRETEN
301
302
303 Retension tape.
304
305
306 MTREW Rewind.
307
308
309 MTSEEK Seek to the tape block number specified in
310 __mt_count__. This operation requires either a SCSI-2
311 drive that supports the LOCATE command
312 (device-specific address) or a Tandberg-compatible SCSI-1
313 drive (Tandberg, Archive Viper, Wangtek, ... ). The block
314 number should be one that was previously returned by
315 MTIOCPOS if device-specific addresses are
316 used.
317
318
319 MTSETBLK
320
321
322 Set the drive's block length to the value specified in
323 __mt_count__. A block length of zero sets the drive to
324 variable block size mode.
325
326
327 MTSETDENSITY
328
329
330 Set the tape density to the code in __mt_count__. The
331 density codes supported by a drive can be found from the
332 drive documentation.
333
334
335 MTSETPART
336
337
338 The active partition is switched to __mt_count .__ The
339 partitions are numbered from zero. This command is not
340 allowed for a drive unless the partition support is enabled
341 for the drive (see MT_ST_CAN_PARTITIONS below).
342
343
344 MTUNLOAD
345
346
347 Execute the SCSI unload command (does not eject the
348 tape).
349
350
351 MTUNLOCK
352
353
354 Unlock the tape drive door.
355
356
357 MTWEOF Write __mt_count__ filemarks.
358
359
360 MTWSM Write __mt_count__ setmarks.
361
362
363 Magnetic Tape operations for setting of device options (by
364 the superuser):
365
366
367 MTSETDRVBUFFER
368
369
370 Set various drive and driver options according to bits
371 encoded in __mt_count__. These consist of the drive's
372 buffering mode, 13 Boolean driver options, the buffer write
373 threshold, defaults for the block size and density, and
374 timeouts (only in kernels
375 __
376
377
378 A value having zeros in the high-order 4 bits will be used
379 to set the drive's buffering mode. The buffering modes
380 are:
381
382
383 0
384
385
386 The drive will not report GOOD status on
387 write commands until the data blocks are actually written to
388 the medium.
389
390
391 1
392
393
394 The drive may report GOOD status on write
395 commands as soon as all the data has been transferred to the
396 drive's internal buffer.
397
398
399 2
400
401
402 The drive may report GOOD status on write
403 commands as soon as (a) all the data has been transferred to
404 the drive's internal buffer, and (b) all buffered data from
405 different initiators has been successfully written to the
406 medium.
407
408
409 To control the write threshold the value in __mt_count__
410 must include the constant
411 MT_ST_WRITE_THRESHOLD logically ORed with a
412 block count in the low 28 bits. The block count refers to
413 1024-byte blocks, not the physical block size on the tape.
414 The threshold cannot exceed the driver's internal buffer
415 size (see __DESCRIPTION__ ,
416 above).
417
418
419 To set and clear the Boolean options the value in
420 __mt_count__ must include one the constants
421 MT_ST_BOOLEANS ,
422 MT_ST_SETBOOLEANS ,
423 MT_ST_CLEARBOOLEANS , or
424 MT_ST_DEFBOOLEANS logically ORed with
425 whatever combination of the following options is desired.
426 Using MT_ST_BOOLEANS the options can be set
427 to the values defined in the corresponding bits. With
428 MT_ST_SETBOOLEANS the options can be
429 selectively set and with MT_ST_DEFBOOLEANS
430 selectively cleared.
431
432
433 The default options for a tape device are set with
434 MT_ST_DEFBOOLEANS . A non-active tape device
435 (e.g., device with minor 32 or 160) is activated when the
436 default options for it are defined the first time. An
437 activated device inherits from the device activated at
438 start-up the options not set explicitly.
439
440
441 The Boolean options are:
442
443
444 MT_ST_BUFFER_WRITES (Default:
445 true)
446
447
448 Buffer all write operations in fixed block mode. If this
449 option is false and the drive uses a fixed block size, then
450 all write operations must be for a multiple of the block
451 size. This option must be set false to write reliable
452 multi-volume archives.
453
454
455 MT_ST_ASYNC_WRITES (Default:
456 true)
457
458
459 When this options is true write operations return
460 immediately without waiting for the data to be transferred
461 to the drive if the data fits into the driver's buffer. The
462 write threshold determines how full the buffer must be
463 before a new SCSI write command is issued. Any errors
464 reported by the drive will be held until the next operation.
465 This option must be set false to write reliable multi-volume
466 archives.
467
468
469 MT_ST_READ_AHEAD (Default: true)
470
471
472 This option causes the driver to provide read buffering and
473 read-ahead in fixed block mode. If this option is false and
474 the drive uses a fixed block size, then all read operations
475 must be for a multiple of the block size.
476
477
478 MT_ST_TWO_FM (Default: false)
479
480
481 This option modifies the driver behavior when a file is
482 closed. The normal action is to write a single filemark. If
483 the option is true the driver will write two filemarks and
484 backspace over the second one.
485
486
487 Note: This option should not be set true for QIC tape drives
488 since they are unable to overwrite a filemark. These drives
489 detect the end of recorded data by testing for blank tape
490 rather than two consecutive filemarks. Most other current
491 drives also detect the end of recorded data and using two
492 filemarks is usually necessary only when interchanging tapes
493 with some other systems.
494
495
496 MT_ST_DEBUGGING (Default: false)
497
498
499 This option turns on various debugging messages from the
500 driver (effective only if the driver was compiled with
501 DEBUG defined non-zero).
502
503
504 MT_ST_FAST_EOM (Default: false)
505
506
507 This option causes the MTEOM operation to be
508 sent directly to the drive, potentially speeding up the
509 operation but causing the driver to lose track of the
510 current file number normally returned by the
511 MTIOCGET request. If
512 MT_ST_FAST_EOM is false the driver will
513 respond to an MTEOM request by forward
514 spacing over files.
515
516
517 MT_ST_AUTO_LOCK (Default: false)
518
519
520 When this option is true, the drive door is locked when the
521 device is opened and unlocked when it is
522 closed.
523
524
525 MT_ST_DEF_WRITES (Default:
526 false)
527
528
529 The tape options (block size, mode, compression, etc.) may
530 change when changing from one device linked to a drive to
531 another device linked to the same drive depending on how the
532 devices are defined. This option defines when the changes
533 are enforced by the driver using SCSI-commands and when the
534 drives auto-detection capabilities are relied upon. If this
535 option is false, the driver sends the SCSI-commands
536 immediately when the device is changed. If the option is
537 true, the SCSI-commands are not sent until a write is
538 requested. In this case the drive firmware is allowed to
539 detect the tape structure when reading and the SCSI-commands
540 are used only to make sure that a tape is written according
541 to the correct specification.
542
543
544 MT_ST_CAN_BSR (Default: false)
545
546
547 When read-ahead is used, the tape must sometimes be spaced
548 backward to the correct position when the device is closed
549 and the SCSI command to space backwards over records is used
550 for this purpose. Some older drives can't process this
551 command reliably and this option can be used to instruct the
552 driver not to use the command. The end result is that, with
553 read-ahead and fixed block mode, the tape may not be
554 correctly positioned within a file when the device is
555 closed.
556
557
558 MT_ST_NO_BLKLIMS (Default:
559 false)
560
561
562 Some drives don't accept the READ BLOCK LIMITS SCSI command.
563 If this is used, the driver does not use the command. The
564 drawback is that the driver can't check before sending
565 commands if the selected block size is acceptable to the
566 drive.
567
568
569 MT_ST_CAN_PARTITIONS (Default:
570 false)
571
572
573 This option enables support for several partitions within a
574 tape. The option applies to all devices linked to a
575 drive.
576
577
578 MT_ST_SCSI2LOGICAL (Default:
579 false)
580
581
582 This option instructs the driver to use the logical block
583 addresses defined in the SCSI-2 standard when performing the
584 seek and tell operations (both with MTSEEK and MTIOCPOS
585 commands and when changing tape partition). Otherwise the
586 device-specific addresses are used. It is highly advisable
587 to set this option if the drive supports the logical
588 addresses because they count also filemarks. There are some
589 drives that only support the logical block
590 addresses.
591
592
593 MT_ST_SYSV (Default: false)
594
595
596 When this option is enabled, the tape devices use the
597 SystemV semantics. Otherwise the BSD semantics are used. The
598 most important difference between the semantics is what
599 happens when a device used for reading is closed: in SYSV
600 semantics the tape is spaced forward past the next filemark
601 if this has not happened while using the device. In BSD
602 semantics the tape position is not changed.
603
604
605 EXAMPLE
606
607
608 __struct mtop__ ''mt_cmd''__;
609 __''mt_cmd.mt_op'' __= MTSETDRVBUFFER;
610 __''mt_cmd.mt_count'' __= MT_ST_BOOLEANS |
611 MT_ST_BUFFER_WRITES |
612 MT_ST_ASYNC_WRITES;
613 ioctl(__''fd''__, MTIOCTOP, ''mt_cmd''__);
614 __
615
616
617 The default block size for a device can be set with
618 MT_ST_DEF_BLKSIZE and the default density
619 code can be set with MT_ST_DEFDENSITY . The
620 values for the parameters are ORed with the operation
621 code.
622
623
624 With kernels 2.1.x and later, the timeout values can be set
625 with the subcommand MT_ST_SET_TIMEOUT or'ed
626 with the timeout in seconds. The long timeout (used for
627 rewinds and other commands that may take a long time) can be
628 set with MT_ST_SET_LONG_TIMEOUT . The kernel
629 defaults are very long to make sure that a successful
630 command is not timed out with any drive. Because of this the
631 driver may seem stuck even if it is only waiting for the
632 timeout. These commands can be used to set more practical
633 values for a specific drive. The timeouts set for one device
634 apply for all devices linked to the same drive.
635
636
637 __MTIOCGET - Get status__
638
639
640 This request takes an argument of type __(struct mtget
641 *)__.
642
643
644 /* structure for MTIOCGET - mag tape get status command */
645 struct mtget {
646 long mt_type;
647 long mt_resid;
648 /* the following registers are device dependent */
649 long mt_dsreg;
650 long mt_gstat;
651 long mt_erreg;
652 /* The next two fields are not always used */
653 daddr_t mt_fileno;
654 daddr_t mt_blkno;
655 };
656 __mt_type__
657
658
659 The header file defines many values for __mt_type__, but
660 the current driver reports only the generic types
661 MT_ISSCSI1 (Generic SCSI-1 tape) and
662 MT_ISSCSI2 (Generic SCSI-2
663 tape).
664
665
666 __mt_resid__
667
668
669 contains the current tape partition number.
670
671
672 __mt_dsreg__
673
674
675 reports the drive's current settings for block size (in the
676 low 24 bits) and density (in the high 8 bits). These fields
677 are defined by MT_ST_BLKSIZE_SHIFT ,
678 MT_ST_BLKSIZE_MASK ,
679 MT_ST_DENSITY_SHIFT , and
680 MT_ST_DENSITY_MASK .
681
682
683 __mt_gstat__
684
685
686 reports generic (device independent) status information. The
687 header file defines macros for testing these status
688 bits:
689
690
691 GMT_EOF( ''x'' ) : The tape
692 is positioned just after a filemark (always false after an
693 MTSEEK operation).
694
695
696 GMT_BOT( ''x'' ) : The tape
697 is positioned at the beginning of the first file (always
698 false after an MTSEEK
699 operation).
700
701
702 GMT_EOT( ''x'' ) : A tape
703 operation has reached the physical End Of Tape.
704
705
706 GMT_SM( ''x'' ) : The tape
707 is currently positioned at a setmark (always false after an
708 MTSEEK operation).
709
710
711 GMT_EOD( ''x'' ) : The tape
712 is positioned at the end of recorded data.
713
714
715 GMT_WR_PROT( ''x'' ) : The
716 drive is write-protected. For some drives this can also mean
717 that the drive does not support writing on the current
718 medium type.
719
720
721 GMT_ONLINE( ''x'' ) : The
722 last __open()__ found the drive with a tape in place and
723 ready for operation.
724
725
726 GMT_D_6250( ''x'' ) ,
727 GMT_D_1600( ''x'' ) ,
728 GMT_D_800( ''x'' ) : This
729 ``generic'' status information reports the current density
730 setting for 9-track
731
732
733 GMT_DR_OPEN( ''x'' ) : The
734 drive does not have a tape in place.
735
736
737 GMT_IM_REP_EN( ''x'' ) :
738 Immediate report mode. This bit is set if there are no
739 guarantees that the data has been physically written to the
740 tape when the write call returns. It is set zero only when
741 the driver does not buffer data and the drive is set not to
742 buffer data.
743
744
745 __mt_erreg__
746
747
748 The only field defined in __mt_erreg__ is the recovered
749 error count in the low 16 bits (as defined by
750 MT_ST_SOFTERR_SHIFT and
751 MT_ST_SOFTERR_MASK ). Due to inconsistencies
752 in the way drives report recovered errors, this count is
753 often not maintained (most drives do not by default report
754 soft errors but this can be changed with a SCSI MODE SELECT
755 command).
756
757
758 __mt_fileno__
759
760
761 reports the current file number (zero-based). This value is
762 set to -1 when the file number is unknown (e.g., after
763 MTBSS or MTSEEK
764 ).
765
766
767 __mt_blkno__
768
769
770 reports the block number (zero-based) within the current
771 file. This value is set to -1 when the block number is
772 unknown (e.g., after MTBSF ,
773 MTBSS , or MTSEEK
774 ).
775
776
777 __MTIOCPOS - Get tape
778 position__
779
780
781 This request takes an argument of type __(struct mtpos
782 *)__ and reports the drive's notion of the current tape
783 block number, which is not the same as __mt_blkno__
784 returned by MTIOCGET . This drive must be a
785 SCSI-2 drive that supports the READ POSITION
786 command (device-specific address) or a Tandberg-compatible
787 SCSI-1 drive (Tandberg, Archive Viper, Wangtek, ...
788 ).
789
790
791 /* structure for MTIOCPOS - mag tape get position command */
792 struct mtpos {
793 long mt_blkno; /* current block number */
794 };
795 !!RETURN VALUE
796
797
798 EIO The requested operation could not be
799 completed.
800
801
802 ENOSPC A write operation could not be completed because the
803 tape reached end-of-medium.
804
805
806 EACCES An attempt was made to write or erase a
807 write-protected tape. (This error is not detected during
808 __open()__.)
809
810
811 EFAULT The command parameters point to memory not belonging
812 to the calling process.
813
814
815 ENXIO During opening, the tape device does not
816 exist.
817
818
819 EBUSY The device is already in use or the driver was unable
820 to allocate a buffer.
821
822
823 EOVERFLOW
824
825
826 An attempt was made to read or write a variable-length block
827 that is larger than the driver's internal
828 buffer.
829
830
831 EINVAL An __ioctl()__ had an illegal argument, or a
832 requested block size was illegal.
833
834
835 ENOSYS Unknown __ioctl()__.
836
837
838 EROFS Open is attempted with O_WRONLY or O_RDWR when the
839 tape in the drive is write-protected.
840 !!FILES
841
842
843 /dev/st* : the auto-rewind SCSI tape devices
844 /dev/nst* : the non-rewind SCSI tape devices
845 !!AUTHOR
846
847
848 The driver has been written by Kai Mkisara
849 (Kai.Makisara@metla.fi) starting from a driver written by
850 Dwayne Forsyth. Several other people have also contributed
851 to the driver.
852 !!SEE ALSO
853
854
855 mt(1)
856
857
858 The file README.st in the kernel sources contains the most
859 recent information about the driver and it's configuration
860 possibilities.
861 !!NOTES
862
863
864 1. When exchanging data between systems, both systems have
865 to agree on the physical tape block size. The parameters of
866 a drive after startup are often not the ones most operating
867 systems use with these devices. Most systems use drives in
868 variable block mode if the drive supports that mode. This
869 applies to most modern drives, including DATs, 8mm helical
870 scan drives, DLTs, etc. It may be advisable use these drives
871 in variable block mode also in Linux (i.e., use MTSETBLK or
872 MTSETDEFBLK at system startup to set the mode), at least
873 when exchanging data with foreign system. The drawback of
874 this is that a fairly large tape block size has to be used
875 to get acceptable data transfer rates on the SCSI
876 bus.
877
878
879 2. Many programs (e.g., tar) allow the user to specify the
880 blocking factor on command line. Note that this determines
881 the physical block size on tape only in variable block
882 mode.
883
884
885 3. In order to use SCSI tape drives, the basic SCSI driver,
886 a SCSI-adapter driver and the SCSI tape driver must be
887 either configured into the kernel or loaded as modules. If
888 the SCSI-tape driver is not present, the drive is recognized
889 but the tape support described in this page is not
890 available.
891
892
893 4. The driver writes error messages to the console/log. The
894 SENSE codes written into some messages are automatically
895 translated to text if verbose SCSI messages are enabled in
896 kernel configuration.
897 !!COPYRIGHT
898
899
900 Copyright 1995 Robert K. Nichols.
901 Copyright 1999 Kai Mkisara.
902
903
904 Permission is granted to make and distribute verbatim copies
905 of this manual provided the copyright notice and this
906 permission notice are preserved on all copies. Additional
907 permissions are contained in the header of the source
908 file.
909 ----
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