1ST(4) Linux Programmer's Manual ST(4)
2
6 st - SCSI tape device
7
9 #include <sys/mtio.h>
10 int ioctl(int fd, int request [, (void *)arg3]);
12 int ioctl(int fd, MTIOCTOP, (struct mtop *)mt_cmd);
13 int ioctl(int fd, MTIOCGET, (struct mtget *)mt_status);
14 int ioctl(int fd, MTIOCPOS, (struct mtpos *)mt_pos);
15
17 The st driver provides the interface to a variety of SCSI tape devices.
18 Currently, the driver takes control of all detected devices of type
19 “sequential-access”. The st driver uses major device number 9.
20 Each device uses eight minor device numbers. The lowermost five bits
22 in the minor numbers are assigned sequentially in the order of detec‐
23 tion. In the 2.6 kernel, the bits above the eight lowermost bits are
24 concatenated to the five lowermost bits to form the tape number. The
25 minor numbers can be grouped into two sets of four numbers: the princi‐
26 pal (auto-rewind) minor device numbers, n, and the “no-rewind” device
27 numbers, (n + 128). Devices opened using the principal device number
28 will be sent a REWIND command when they are closed. Devices opened
29 using the “no-rewind” device number will not. (Note that using an
30 auto-rewind device for positioning the tape with, for instance, mt does
31 not lead to the desired result: the tape is rewound after the mt com‐
32 mand and the next command starts from the beginning of the tape).
33 Within each group, four minor numbers are available to define devices
35 with different characteristics (block size, compression, density, etc.)
36 When the system starts up, only the first device is available. The
37 other three are activated when the default characteristics are defined
38 (see below). (By changing compile-time constants, it is possible to
39 change the balance between the maximum number of tape drives and the
40 number of minor numbers for each drive. The default allocation allows
41 control of 32 tape drives. For instance, it is possible to control up
42 to 64 tape drives with two minor numbers for different options.)
43 Devices are typically created by:
45 mknod -m 666 /dev/st0 c 9 0
47 mknod -m 666 /dev/st0l c 9 32
48 mknod -m 666 /dev/st0m c 9 64
49 mknod -m 666 /dev/st0a c 9 96
50 mknod -m 666 /dev/nst0 c 9 128
51 mknod -m 666 /dev/nst0l c 9 160
52 mknod -m 666 /dev/nst0m c 9 192
53 mknod -m 666 /dev/nst0a c 9 224
54 There is no corresponding block device.
56 The driver uses an internal buffer that has to be large enough to hold
58 at least one tape block. In kernels before 2.1.121, the buffer is
59 allocated as one contiguous block. This limits the block size to the
60 largest contiguous block of memory the kernel allocator can provide.
61 The limit is currently 128 kB for 32-bit architectures and 256 kB for
62 64-bit architectures. In newer kernels the driver allocates the buffer
63 in several parts if necessary. By default, the maximum number of parts
64 is 16. This means that the maximum block size is very large (2 MB if
65 allocation of 16 blocks of 128 kB succeeds).
66 The driver's internal buffer size is determined by a compile-time con‐
68 stant which can be overridden with a kernel startup option. In addi‐
69 tion to this, the driver tries to allocate a larger temporary buffer at
70 run time if necessary. However, run-time allocation of large contigu‐
71 ous blocks of memory may fail and it is advisable not to rely too much
72 on dynamic buffer allocation with kernels older than 2.1.121 (this
73 applies also to demand-loading the driver with kerneld or kmod).
74 The driver does not specifically support any tape drive brand or model.
76 After system start-up the tape device options are defined by the drive
77 firmware. For example, if the drive firmware selects fixed-block mode,
78 the tape device uses fixed-block mode. The options can be changed with
79 explicit ioctl(2) calls and remain in effect when the device is closed
80 and reopened. Setting the options affects both the auto-rewind and the
81 nonrewind device.
82 Different options can be specified for the different devices within the
84 subgroup of four. The options take effect when the device is opened.
85 For example, the system administrator can define one device that writes
86 in fixed-block mode with a certain block size, and one which writes in
87 variable-block mode (if the drive supports both modes).
88 The driver supports tape partitions if they are supported by the drive.
90 (Note that the tape partitions have nothing to do with disk partitions.
91 A partitioned tape can be seen as several logical tapes within one
92 medium.) Partition support has to be enabled with an ioctl(2). The
93 tape location is preserved within each partition across partition
94 changes. The partition used for subsequent tape operations is selected
95 with an ioctl(2). The partition switch is executed together with the
96 next tape operation in order to avoid unnecessary tape movement. The
97 maximum number of partitions on a tape is defined by a compile-time
98 constant (originally four). The driver contains an ioctl(2) that can
99 format a tape with either one or two partitions.
100 Device /dev/tape is usually created as a hard or soft link to the
102 default tape device on the system.
103 Starting from kernel 2.6.2, the driver exports in the sysfs directory
105 /sys/class/scsi_tape the attached devices and some parameters assigned
106 to the devices.
107 Data transfer
109 The driver supports operation in both fixed-block mode and variable-
110 block mode (if supported by the drive). In fixed-block mode the drive
111 writes blocks of the specified size and the block size is not dependent
112 on the byte counts of the write system calls. In variable-block mode
113 one tape block is written for each write call and the byte count deter‐
114 mines the size of the corresponding tape block. Note that the blocks
115 on the tape don't contain any information about the writing mode: when
116 reading, the only important thing is to use commands that accept the
117 block sizes on the tape.
118 In variable-block mode the read byte count does not have to match the
120 tape block size exactly. If the byte count is larger than the next
121 block on tape, the driver returns the data and the function returns the
122 actual block size. If the block size is larger than the byte count, an
123 error is returned.
124 In fixed-block mode the read byte counts can be arbitrary if buffering
126 is enabled, or a multiple of the tape block size if buffering is dis‐
127 abled. Kernels before 2.1.121 allow writes with arbitrary byte count
128 if buffering is enabled. In all other cases (kernel before 2.1.121
129 with buffering disabled or newer kernel) the write byte count must be a
130 multiple of the tape block size.
131 In the 2.6 kernel, the driver tries to use direct transfers between the
133 user buffer and the device. If this is not possible, the driver's
134 internal buffer is used. The reasons for not using direct transfers
135 include improper alignment of the user buffer (default is 512 bytes but
136 this can be changed by the HBA driver), one or more pages of the user
137 buffer not reachable by the SCSI adapter, and so on.
138 A filemark is automatically written to tape if the last tape operation
140 before close was a write.
141 When a filemark is encountered while reading, the following happens.
143 If there are data remaining in the buffer when the filemark is found,
144 the buffered data is returned. The next read returns zero bytes. The
145 following read returns data from the next file. The end of recorded
146 data is signaled by returning zero bytes for two consecutive read
147 calls. The third read returns an error.
148 Ioctls
150 The driver supports three ioctl(2) requests. Requests not recognized
151 by the st driver are passed to the SCSI driver. The definitions below
152 are from /usr/include/linux/mtio.h:
153 MTIOCTOP — perform a tape operation
155 This request takes an argument of type (struct mtop *). Not all drives
156 support all operations. The driver returns an EIO error if the drive
157 rejects an operation.
158 /* Structure for MTIOCTOP - mag tape op command: */
160 struct mtop {
161 short mt_op; /* operations defined below */
162 int mt_count; /* how many of them */
163 };
164 Magnetic Tape operations for normal tape use:
166 MTBSF Backward space over mt_count filemarks.
168 MTBSFM Backward space over mt_count filemarks. Reposition the
170 tape to the EOT side of the last filemark.
171 MTBSR Backward space over mt_count records (tape blocks).
173 MTBSS Backward space over mt_count setmarks.
175 MTCOMPRESSION Enable compression of tape data within the drive if
177 mt_count is nonzero and disable compression if mt_count
178 is zero. This command uses the MODE page 15 supported by
179 most DATs.
180 MTEOM Go to the end of the recorded media (for appending
182 files).
183 MTERASE Erase tape. With 2.6 kernel, short erase (mark tape
185 empty) is performed if the argument is zero. Otherwise,
186 long erase (erase all) is done.
187 MTFSF Forward space over mt_count filemarks.
189 MTFSFM Forward space over mt_count filemarks. Reposition the
191 tape to the BOT side of the last filemark.
192 MTFSR Forward space over mt_count records (tape blocks).
194 MTFSS Forward space over mt_count setmarks.
196 MTLOAD Execute the SCSI load command. A special case is avail‐
198 able for some HP autoloaders. If mt_count is the con‐
199 stant MT_ST_HPLOADER_OFFSET plus a number, the number is
200 sent to the drive to control the autoloader.
201 MTLOCK Lock the tape drive door.
203 MTMKPART Format the tape into one or two partitions. If mt_count
205 is positive, it gives the size of partition 1 and parti‐
206 tion 0 contains the rest of the tape. If mt_count is
207 zero, the tape is formatted into one partition. From
208 kernel version 4.6, a negative mt_count specifies the
209 size of partition 0 and the rest of the tape contains
210 partition 1. The physical ordering of partitions depends
211 on the drive. This command is not allowed for a drive
212 unless the partition support is enabled for the drive
213 (see MT_ST_CAN_PARTITIONS below).
214 MTNOP No op—flushes the driver's buffer as a side effect.
216 Should be used before reading status with MTIOCGET.
217 MTOFFL Rewind and put the drive off line.
219 MTRESET Reset drive.
221 MTRETEN Re-tension tape.
223 MTREW Rewind.
225 MTSEEK Seek to the tape block number specified in mt_count.
227 This operation requires either a SCSI-2 drive that sup‐
228 ports the LOCATE command (device-specific address) or a
229 Tandberg-compatible SCSI-1 drive (Tandberg, Archive
230 Viper, Wangtek, ...). The block number should be one
231 that was previously returned by MTIOCPOS if device-spe‐
232 cific addresses are used.
233 MTSETBLK Set the drive's block length to the value specified in
235 mt_count. A block length of zero sets the drive to vari‐
236 able block size mode.
237 MTSETDENSITY Set the tape density to the code in mt_count. The den‐
239 sity codes supported by a drive can be found from the
240 drive documentation.
241 MTSETPART The active partition is switched to mt_count. The parti‐
243 tions are numbered from zero. This command is not
244 allowed for a drive unless the partition support is
245 enabled for the drive (see MT_ST_CAN_PARTITIONS below).
246 MTUNLOAD Execute the SCSI unload command (does not eject the
248 tape).
249 MTUNLOCK Unlock the tape drive door.
251 MTWEOF Write mt_count filemarks.
253 MTWSM Write mt_count setmarks.
255 Magnetic Tape operations for setting of device options (by the supe‐
257 ruser):
258 MTSETDRVBUFFER
260 Set various drive and driver options according to bits encoded
261 in mt_count. These consist of the drive's buffering mode, a
262 set of Boolean driver options, the buffer write threshold,
263 defaults for the block size and density, and timeouts (only in
264 kernels 2.1 and later). A single operation can affect only one
265 item in the list above (the Booleans counted as one item.)
266 A value having zeros in the high-order 4 bits will be used to
268 set the drive's buffering mode. The buffering modes are:
269 0 The drive will not report GOOD status on write commands
271 until the data blocks are actually written to the
272 medium.
273 1 The drive may report GOOD status on write commands as
275 soon as all the data has been transferred to the
276 drive's internal buffer.
277 2 The drive may report GOOD status on write commands as
279 soon as (a) all the data has been transferred to the
280 drive's internal buffer, and (b) all buffered data from
281 different initiators has been successfully written to
282 the medium.
283 To control the write threshold the value in mt_count must
285 include the constant MT_ST_WRITE_THRESHOLD bitwise ORed with a
286 block count in the low 28 bits. The block count refers to
287 1024-byte blocks, not the physical block size on the tape. The
288 threshold cannot exceed the driver's internal buffer size (see
289 DESCRIPTION, above).
290 To set and clear the Boolean options the value in mt_count must
292 include one of the constants MT_ST_BOOLEANS, MT_ST_SETBOOLEANS,
293 MT_ST_CLEARBOOLEANS, or MT_ST_DEFBOOLEANS bitwise ORed with
294 whatever combination of the following options is desired.
295 Using MT_ST_BOOLEANS the options can be set to the values
296 defined in the corresponding bits. With MT_ST_SETBOOLEANS the
297 options can be selectively set and with MT_ST_DEFBOOLEANS
298 selectively cleared.
299 The default options for a tape device are set with MT_ST_DEF‐
301 BOOLEANS. A nonactive tape device (e.g., device with minor 32
302 or 160) is activated when the default options for it are
303 defined the first time. An activated device inherits from the
304 device activated at start-up the options not set explicitly.
305 The Boolean options are:
307 MT_ST_BUFFER_WRITES (Default: true)
309 Buffer all write operations in fixed-block mode. If
310 this option is false and the drive uses a fixed block
311 size, then all write operations must be for a multiple
312 of the block size. This option must be set false to
313 write reliable multivolume archives.
314 MT_ST_ASYNC_WRITES (Default: true)
316 When this option is true, write operations return imme‐
317 diately without waiting for the data to be transferred
318 to the drive if the data fits into the driver's buffer.
319 The write threshold determines how full the buffer must
320 be before a new SCSI write command is issued. Any
321 errors reported by the drive will be held until the next
322 operation. This option must be set false to write reli‐
323 able multivolume archives.
324 MT_ST_READ_AHEAD (Default: true)
326 This option causes the driver to provide read buffering
327 and read-ahead in fixed-block mode. If this option is
328 false and the drive uses a fixed block size, then all
329 read operations must be for a multiple of the block
330 size.
331 MT_ST_TWO_FM (Default: false)
333 This option modifies the driver behavior when a file is
334 closed. The normal action is to write a single file‐
335 mark. If the option is true, the driver will write two
336 filemarks and backspace over the second one.
337 Note: This option should not be set true for QIC tape
339 drives since they are unable to overwrite a filemark.
340 These drives detect the end of recorded data by testing
341 for blank tape rather than two consecutive filemarks.
342 Most other current drives also detect the end of
343 recorded data and using two filemarks is usually neces‐
344 sary only when interchanging tapes with some other sys‐
345 tems.
346 MT_ST_DEBUGGING (Default: false)
348 This option turns on various debugging messages from the
349 driver (effective only if the driver was compiled with
350 DEBUG defined nonzero).
351 MT_ST_FAST_EOM (Default: false)
353 This option causes the MTEOM operation to be sent
354 directly to the drive, potentially speeding up the oper‐
355 ation but causing the driver to lose track of the cur‐
356 rent file number normally returned by the MTIOCGET
357 request. If MT_ST_FAST_EOM is false, the driver will
358 respond to an MTEOM request by forward spacing over
359 files.
360 MT_ST_AUTO_LOCK (Default: false)
362 When this option is true, the drive door is locked when
363 the device is opened and unlocked when it is closed.
364 MT_ST_DEF_WRITES (Default: false)
366 The tape options (block size, mode, compression, etc.)
367 may change when changing from one device linked to a
368 drive to another device linked to the same drive depend‐
369 ing on how the devices are defined. This option defines
370 when the changes are enforced by the driver using SCSI-
371 commands and when the drives auto-detection capabilities
372 are relied upon. If this option is false, the driver
373 sends the SCSI-commands immediately when the device is
374 changed. If the option is true, the SCSI-commands are
375 not sent until a write is requested. In this case, the
376 drive firmware is allowed to detect the tape structure
377 when reading and the SCSI-commands are used only to make
378 sure that a tape is written according to the correct
379 specification.
380 MT_ST_CAN_BSR (Default: false)
382 When read-ahead is used, the tape must sometimes be
383 spaced backward to the correct position when the device
384 is closed and the SCSI command to space backward over
385 records is used for this purpose. Some older drives
386 can't process this command reliably and this option can
387 be used to instruct the driver not to use the command.
388 The end result is that, with read-ahead and fixed-block
389 mode, the tape may not be correctly positioned within a
390 file when the device is closed. With 2.6 kernel, the
391 default is true for drives supporting SCSI-3.
392 MT_ST_NO_BLKLIMS (Default: false)
394 Some drives don't accept the READ BLOCK LIMITS SCSI com‐
395 mand. If this is used, the driver does not use the com‐
396 mand. The drawback is that the driver can't check
397 before sending commands if the selected block size is
398 acceptable to the drive.
399 MT_ST_CAN_PARTITIONS (Default: false)
401 This option enables support for several partitions
402 within a tape. The option applies to all devices linked
403 to a drive.
404 MT_ST_SCSI2LOGICAL (Default: false)
406 This option instructs the driver to use the logical
407 block addresses defined in the SCSI-2 standard when per‐
408 forming the seek and tell operations (both with MTSEEK
409 and MTIOCPOS commands and when changing tape partition).
410 Otherwise, the device-specific addresses are used. It
411 is highly advisable to set this option if the drive sup‐
412 ports the logical addresses because they count also
413 filemarks. There are some drives that support only the
414 logical block addresses.
415 MT_ST_SYSV (Default: false)
417 When this option is enabled, the tape devices use the
418 SystemV semantics. Otherwise, the BSD semantics are
419 used. The most important difference between the seman‐
420 tics is what happens when a device used for reading is
421 closed: in System V semantics the tape is spaced forward
422 past the next filemark if this has not happened while
423 using the device. In BSD semantics the tape position is
424 not changed.
425 MT_NO_WAIT (Default: false)
427 Enables immediate mode (i.e., don't wait for the command
428 to finish) for some commands (e.g., rewind).
429 An example:
431 struct mtop mt_cmd;
433 mt_cmd.mt_op = MTSETDRVBUFFER;
434 mt_cmd.mt_count = MT_ST_BOOLEANS |
435 MT_ST_BUFFER_WRITES | MT_ST_ASYNC_WRITES;
436 ioctl(fd, MTIOCTOP, mt_cmd);
437 The default block size for a device can be set with
439 MT_ST_DEF_BLKSIZE and the default density code can be set with
440 MT_ST_DEFDENSITY. The values for the parameters are or'ed with
441 the operation code.
442 With kernels 2.1.x and later, the timeout values can be set
444 with the subcommand MT_ST_SET_TIMEOUT ORed with the timeout in
445 seconds. The long timeout (used for rewinds and other commands
446 that may take a long time) can be set with MT_ST_SET_LONG_TIME‐
447 OUT. The kernel defaults are very long to make sure that a
448 successful command is not timed out with any drive. Because of
449 this, the driver may seem stuck even if it is only waiting for
450 the timeout. These commands can be used to set more practical
451 values for a specific drive. The timeouts set for one device
452 apply for all devices linked to the same drive.
453 Starting from kernels 2.4.19 and 2.5.43, the driver supports a
455 status bit which indicates whether the drive requests cleaning.
456 The method used by the drive to return cleaning information is
457 set using the MT_ST_SEL_CLN subcommand. If the value is zero,
458 the cleaning bit is always zero. If the value is one, the
459 TapeAlert data defined in the SCSI-3 standard is used (not yet
460 implemented). Values 2–17 are reserved. If the lowest eight
461 bits are >= 18, bits from the extended sense data are used.
462 The bits 9–16 specify a mask to select the bits to look at and
463 the bits 17–23 specify the bit pattern to look for. If the bit
464 pattern is zero, one or more bits under the mask indicate the
465 cleaning request. If the pattern is nonzero, the pattern must
466 match the masked sense data byte.
467 MTIOCGET — get status
469 This request takes an argument of type (struct mtget *).
470 /* structure for MTIOCGET - mag tape get status command */
472 struct mtget {
473 long mt_type;
474 long mt_resid;
475 /* the following registers are device dependent */
476 long mt_dsreg;
477 long mt_gstat;
478 long mt_erreg;
479 /* The next two fields are not always used */
480 daddr_t mt_fileno;
481 daddr_t mt_blkno;
482 };
483 mt_type The header file defines many values for mt_type, but the
485 current driver reports only the generic types MT_ISSCSI1
486 (Generic SCSI-1 tape) and MT_ISSCSI2 (Generic SCSI-2 tape).
487 mt_resid contains the current tape partition number.
489 mt_dsreg reports the drive's current settings for block size (in the
491 low 24 bits) and density (in the high 8 bits). These fields
492 are defined by MT_ST_BLKSIZE_SHIFT, MT_ST_BLKSIZE_MASK,
493 MT_ST_DENSITY_SHIFT, and MT_ST_DENSITY_MASK.
494 mt_gstat reports generic (device independent) status information.
496 The header file defines macros for testing these status
497 bits:
498 GMT_EOF(x): The tape is positioned just after a filemark
500 (always false after an MTSEEK operation).
501 GMT_BOT(x): The tape is positioned at the beginning of the
503 first file (always false after an MTSEEK operation).
504 GMT_EOT(x): A tape operation has reached the physical End Of
506 Tape.
507 GMT_SM(x): The tape is currently positioned at a setmark
509 (always false after an MTSEEK operation).
510 GMT_EOD(x): The tape is positioned at the end of recorded
512 data.
513 GMT_WR_PROT(x): The drive is write-protected. For some
515 drives this can also mean that the drive does not sup‐
516 port writing on the current medium type.
517 GMT_ONLINE(x): The last open(2) found the drive with a tape
519 in place and ready for operation.
520 GMT_D_6250(x), GMT_D_1600(x), GMT_D_800(x): This “generic”
522 status information reports the current density setting
523 for 9-track ½" tape drives only.
524 GMT_DR_OPEN(x): The drive does not have a tape in place.
526 GMT_IM_REP_EN(x): Immediate report mode. This bit is set if
528 there are no guarantees that the data has been physi‐
529 cally written to the tape when the write call returns.
530 It is set zero only when the driver does not buffer data
531 and the drive is set not to buffer data.
532 GMT_CLN(x): The drive has requested cleaning. Implemented
534 in kernels since 2.4.19 and 2.5.43.
535 mt_erreg The only field defined in mt_erreg is the recovered error
537 count in the low 16 bits (as defined by MT_ST_SOFTERR_SHIFT
538 and MT_ST_SOFTERR_MASK. Due to inconsistencies in the way
539 drives report recovered errors, this count is often not
540 maintained (most drives do not by default report soft errors
541 but this can be changed with a SCSI MODE SELECT command).
542 mt_fileno reports the current file number (zero-based). This value is
544 set to -1 when the file number is unknown (e.g., after MTBSS
545 or MTSEEK).
546 mt_blkno reports the block number (zero-based) within the current
548 file. This value is set to -1 when the block number is
549 unknown (e.g., after MTBSF, MTBSS, or MTSEEK).
550 MTIOCPOS — get tape position
552 This request takes an argument of type (struct mtpos *) and reports the
553 drive's notion of the current tape block number, which is not the same
554 as mt_blkno returned by MTIOCGET. This drive must be a SCSI-2 drive
555 that supports the READ POSITION command (device-specific address) or a
556 Tandberg-compatible SCSI-1 drive (Tandberg, Archive Viper, Wangtek, ...
557 ).
558 /* structure for MTIOCPOS - mag tape get position command */
560 struct mtpos {
561 long mt_blkno; /* current block number */
562 };
563
565 EACCES An attempt was made to write or erase a write-pro‐
566 tected tape. (This error is not detected during
567 open(2).)
568 EBUSY The device is already in use or the driver was
570 unable to allocate a buffer.
571 EFAULT The command parameters point to memory not belong‐
573 ing to the calling process.
574 EINVAL An ioctl(2) had an invalid argument, or a
576 requested block size was invalid.
577 EIO The requested operation could not be completed.
579 ENOMEM The byte count in read(2) is smaller than the next
581 physical block on the tape. (Before 2.2.18 and
582 2.4.0 the extra bytes have been silently ignored.)
583 ENOSPC A write operation could not be completed because
585 the tape reached end-of-medium.
586 ENOSYS Unknown ioctl(2).
588 ENXIO During opening, the tape device does not exist.
590 EOVERFLOW An attempt was made to read or write a variable-
592 length block that is larger than the driver's
593 internal buffer.
594 EROFS Open is attempted with O_WRONLY or O_RDWR when the
596 tape in the drive is write-protected.
597
599 /dev/st*
600 the auto-rewind SCSI tape devices
601 /dev/nst*
603 the nonrewind SCSI tape devices
604
606 1. When exchanging data between systems, both systems have to
607 agree on the physical tape block size. The parameters of a
608 drive after startup are often not the ones most operating
609 systems use with these devices. Most systems use drives in
610 variable-block mode if the drive supports that mode. This
611 applies to most modern drives, including DATs, 8mm helical
612 scan drives, DLTs, etc. It may be advisable to use these
613 drives in variable-block mode also in Linux (i.e., use
614 MTSETBLK or MTSETDEFBLK at system startup to set the mode),
615 at least when exchanging data with a foreign system. The
616 drawback of this is that a fairly large tape block size has
617 to be used to get acceptable data transfer rates on the SCSI
618 bus.
619 2. Many programs (e.g., tar(1)) allow the user to specify the
621 blocking factor on the command line. Note that this deter‐
622 mines the physical block size on tape only in variable-block
623 mode.
624 3. In order to use SCSI tape drives, the basic SCSI driver, a
626 SCSI-adapter driver and the SCSI tape driver must be either
627 configured into the kernel or loaded as modules. If the
628 SCSI-tape driver is not present, the drive is recognized but
629 the tape support described in this page is not available.
630 4. The driver writes error messages to the console/log. The
632 SENSE codes written into some messages are automatically
633 translated to text if verbose SCSI messages are enabled in
634 kernel configuration.
635 5. The driver's internal buffering allows good throughput in
637 fixed-block mode also with small read(2) and write(2) byte
638 counts. With direct transfers this is not possible and may
639 cause a surprise when moving to the 2.6 kernel. The solu‐
640 tion is to tell the software to use larger transfers (often
641 telling it to use larger blocks). If this is not possible,
642 direct transfers can be disabled.
643
645 mt(1)
646 The file drivers/scsi/README.st or Documentation/scsi/st.txt
648 (kernel >= 2.6) in the Linux kernel source tree contains the
649 most recent information about the driver and its configuration
650 possibilities
651
653 This page is part of release 5.04 of the Linux man-pages
654 project. A description of the project, information about
655 reporting bugs, and the latest version of this page, can be
656 found at https://www.kernel.org/doc/man-pages/.
657Linux 2019-03-06 ST(4)