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,
123 the requested amount of data from the start of the block is returned
124 and the rest of the block is discarded.
125 In fixed-block mode the read byte counts can be arbitrary if buffering
127 is enabled, or a multiple of the tape block size if buffering is dis‐
128 abled. Kernels before 2.1.121 allow writes with arbitrary byte count
129 if buffering is enabled. In all other cases (kernel before 2.1.121
130 with buffering disabled or newer kernel) the write byte count must be a
131 multiple of the tape block size.
132 In the 2.6 kernel, the driver tries to use direct transfers between the
134 user buffer and the device. If this is not possible, the driver's
135 internal buffer is used. The reasons for not using direct transfers
136 include improper alignment of the user buffer (default is 512 bytes but
137 this can be changed by the HBA driver), one of more pages of the user
138 buffer not reachable by the SCSI adapter, etc.
139 A filemark is automatically written to tape if the last tape operation
141 before close was a write.
142 When a filemark is encountered while reading, the following happens.
144 If there are data remaining in the buffer when the filemark is found,
145 the buffered data is returned. The next read returns zero bytes. The
146 following read returns data from the next file. The end of recorded
147 data is signaled by returning zero bytes for two consecutive read
148 calls. The third read returns an error.
149 Ioctls
151 The driver supports three ioctl(2) requests. Requests not recognized
152 by the st driver are passed to the SCSI driver. The definitions below
153 are from /usr/include/linux/mtio.h:
154 MTIOCTOP — Perform a tape operation
156 This request takes an argument of type (struct mtop *). Not all drives
157 support all operations. The driver returns an EIO error if the drive
158 rejects an operation.
159 /* Structure for MTIOCTOP - mag tape op command: */
161 struct mtop {
162 short mt_op; /* operations defined below */
163 int mt_count; /* how many of them */
164 };
165 Magnetic Tape operations for normal tape use:
167 MTBSF Backward space over mt_count filemarks.
169 MTBSFM Backward space over mt_count filemarks. Reposition the
171 tape to the EOT side of the last filemark.
172 MTBSR Backward space over mt_count records (tape blocks).
174 MTBSS Backward space over mt_count setmarks.
176 MTCOMPRESSION Enable compression of tape data within the drive if
178 mt_count is nonzero and disable compression if mt_count
179 is zero. This command uses the MODE page 15 supported by
180 most DATs.
181 MTEOM Go to the end of the recorded media (for appending
183 files).
184 MTERASE Erase tape. With 2.6 kernel, short erase (mark tape
186 empty) is performed if the argument is zero. Otherwise
187 long erase (erase all) is done.
188 MTFSF Forward space over mt_count filemarks.
190 MTFSFM Forward space over mt_count filemarks. Reposition the
192 tape to the BOT side of the last filemark.
193 MTFSR Forward space over mt_count records (tape blocks).
195 MTFSS Forward space over mt_count setmarks.
197 MTLOAD Execute the SCSI load command. A special case is avail‐
199 able for some HP autoloaders. If mt_count is the con‐
200 stant MT_ST_HPLOADER_OFFSET plus a number, the number is
201 sent to the drive to control the autoloader.
202 MTLOCK Lock the tape drive door.
204 MTMKPART Format the tape into one or two partitions. If mt_count
206 is nonzero, it gives the size of the first partition and
207 the second partition contains the rest of the tape. If
208 mt_count is zero, the tape is formatted into one parti‐
209 tion. This command is not allowed for a drive unless the
210 partition support is enabled for the drive (see
211 MT_ST_CAN_PARTITIONS below).
212 MTNOP No op — flushes the driver's buffer as a side effect.
214 Should be used before reading status with MTIOCGET.
215 MTOFFL Rewind and put the drive off line.
217 MTRESET Reset drive.
219 MTRETEN Re-tension tape.
221 MTREW Rewind.
223 MTSEEK Seek to the tape block number specified in mt_count.
225 This operation requires either a SCSI-2 drive that sup‐
226 ports the LOCATE command (device-specific address) or a
227 Tandberg-compatible SCSI-1 drive (Tandberg, Archive
228 Viper, Wangtek, ...). The block number should be one
229 that was previously returned by MTIOCPOS if device-spe‐
230 cific addresses are used.
231 MTSETBLK Set the drive's block length to the value specified in
233 mt_count. A block length of zero sets the drive to vari‐
234 able block size mode.
235 MTSETDENSITY Set the tape density to the code in mt_count. The den‐
237 sity codes supported by a drive can be found from the
238 drive documentation.
239 MTSETPART The active partition is switched to mt_count. The parti‐
241 tions are numbered from zero. This command is not
242 allowed for a drive unless the partition support is
243 enabled for the drive (see MT_ST_CAN_PARTITIONS below).
244 MTUNLOAD Execute the SCSI unload command (does not eject the
246 tape).
247 MTUNLOCK Unlock the tape drive door.
249 MTWEOF Write mt_count filemarks.
251 MTWSM Write mt_count setmarks.
253 Magnetic Tape operations for setting of device options (by the supe‐
255 ruser):
256 MTSETDRVBUFFER
258 Set various drive and driver options according to bits encoded
259 in mt_count. These consist of the drive's buffering mode, a
260 set of Boolean driver options, the buffer write threshold,
261 defaults for the block size and density, and timeouts (only in
262 kernels 2.1 and later). A single operation can affect only one
263 item in the list above (the Booleans counted as one item.)
264 A value having zeros in the high-order 4 bits will be used to
266 set the drive's buffering mode. The buffering modes are:
267 0 The drive will not report GOOD status on write commands
269 until the data blocks are actually written to the
270 medium.
271 1 The drive may report GOOD status on write commands as
273 soon as all the data has been transferred to the
274 drive's internal buffer.
275 2 The drive may report GOOD status on write commands as
277 soon as (a) all the data has been transferred to the
278 drive's internal buffer, and (b) all buffered data from
279 different initiators has been successfully written to
280 the medium.
281 To control the write threshold the value in mt_count must
283 include the constant MT_ST_WRITE_THRESHOLD logically ORed with
284 a block count in the low 28 bits. The block count refers to
285 1024-byte blocks, not the physical block size on the tape. The
286 threshold cannot exceed the driver's internal buffer size (see
287 DESCRIPTION, above).
288 To set and clear the Boolean options the value in mt_count must
290 include one of the constants MT_ST_BOOLEANS, MT_ST_SETBOOLEANS,
291 MT_ST_CLEARBOOLEANS, or MT_ST_DEFBOOLEANS logically or'ed with
292 whatever combination of the following options is desired.
293 Using MT_ST_BOOLEANS the options can be set to the values
294 defined in the corresponding bits. With MT_ST_SETBOOLEANS the
295 options can be selectively set and with MT_ST_DEFBOOLEANS
296 selectively cleared.
297 The default options for a tape device are set with MT_ST_DEF‐
299 BOOLEANS. A nonactive tape device (e.g., device with minor 32
300 or 160) is activated when the default options for it are
301 defined the first time. An activated device inherits from the
302 device activated at start-up the options not set explicitly.
303 The Boolean options are:
305 MT_ST_BUFFER_WRITES (Default: true)
307 Buffer all write operations in fixed-block mode. If
308 this option is false and the drive uses a fixed block
309 size, then all write operations must be for a multiple
310 of the block size. This option must be set false to
311 write reliable multivolume archives. MT_ST_ASYNC_WRITES
312 (Default: true) When this option is true, write opera‐
313 tions return immediately without waiting for the data to
314 be transferred to the drive if the data fits into the
315 driver's buffer. The write threshold determines how
316 full the buffer must be before a new SCSI write command
317 is issued. Any errors reported by the drive will be
318 held until the next operation. This option must be set
319 false to write reliable multivolume archives.
320 MT_ST_READ_AHEAD (Default: true)
322 This option causes the driver to provide read buffering
323 and read-ahead in fixed-block mode. If this option is
324 false and the drive uses a fixed block size, then all
325 read operations must be for a multiple of the block
326 size.
327 MT_ST_TWO_FM (Default: false)
329 This option modifies the driver behavior when a file is
330 closed. The normal action is to write a single file‐
331 mark. If the option is true the driver will write two
332 filemarks and backspace over the second one.
333 Note: This option should not be set true for QIC tape
335 drives since they are unable to overwrite a filemark.
336 These drives detect the end of recorded data by testing
337 for blank tape rather than two consecutive filemarks.
338 Most other current drives also detect the end of
339 recorded data and using two filemarks is usually neces‐
340 sary only when interchanging tapes with some other sys‐
341 tems.
342 MT_ST_DEBUGGING (Default: false)
344 This option turns on various debugging messages from the
345 driver (effective only if the driver was compiled with
346 DEBUG defined nonzero).
347 MT_ST_FAST_EOM (Default: false)
349 This option causes the MTEOM operation to be sent
350 directly to the drive, potentially speeding up the oper‐
351 ation but causing the driver to lose track of the cur‐
352 rent file number normally returned by the MTIOCGET
353 request. If MT_ST_FAST_EOM is false the driver will
354 respond to an MTEOM request by forward spacing over
355 files.
356 MT_ST_AUTO_LOCK (Default: false)
358 When this option is true, the drive door is locked when
359 the device is opened and unlocked when it is closed.
360 MT_ST_DEF_WRITES (Default: false)
362 The tape options (block size, mode, compression, etc.)
363 may change when changing from one device linked to a
364 drive to another device linked to the same drive depend‐
365 ing on how the devices are defined. This option defines
366 when the changes are enforced by the driver using SCSI-
367 commands and when the drives auto-detection capabilities
368 are relied upon. If this option is false, the driver
369 sends the SCSI-commands immediately when the device is
370 changed. If the option is true, the SCSI-commands are
371 not sent until a write is requested. In this case the
372 drive firmware is allowed to detect the tape structure
373 when reading and the SCSI-commands are used only to make
374 sure that a tape is written according to the correct
375 specification.
376 MT_ST_CAN_BSR (Default: false)
378 When read-ahead is used, the tape must sometimes be
379 spaced backward to the correct position when the device
380 is closed and the SCSI command to space backwards over
381 records is used for this purpose. Some older drives
382 can't process this command reliably and this option can
383 be used to instruct the driver not to use the command.
384 The end result is that, with read-ahead and fixed-block
385 mode, the tape may not be correctly positioned within a
386 file when the device is closed. With 2.6 kernel, the
387 default is true for drives supporting SCSI-3.
388 MT_ST_NO_BLKLIMS (Default: false)
390 Some drives don't accept the READ BLOCK LIMITS SCSI com‐
391 mand. If this is used, the driver does not use the com‐
392 mand. The drawback is that the driver can't check
393 before sending commands if the selected block size is
394 acceptable to the drive.
395 MT_ST_CAN_PARTITIONS (Default: false)
397 This option enables support for several partitions
398 within a tape. The option applies to all devices linked
399 to a drive.
400 MT_ST_SCSI2LOGICAL (Default: false)
402 This option instructs the driver to use the logical
403 block addresses defined in the SCSI-2 standard when per‐
404 forming the seek and tell operations (both with MTSEEK
405 and MTIOCPOS commands and when changing tape partition).
406 Otherwise the device-specific addresses are used. It is
407 highly advisable to set this option if the drive sup‐
408 ports the logical addresses because they count also
409 filemarks. There are some drives that only support the
410 logical block addresses.
411 MT_ST_SYSV (Default: false)
413 When this option is enabled, the tape devices use the
414 SystemV semantics. Otherwise the BSD semantics are
415 used. The most important difference between the seman‐
416 tics is what happens when a device used for reading is
417 closed: in System V semantics the tape is spaced forward
418 past the next filemark if this has not happened while
419 using the device. In BSD semantics the tape position is
420 not changed.
421 MT_NO_WAIT (Default: false)
423 Enables immediate mode (i.e., don't wait for the command
424 to finish) for some commands (e.g., rewind).
425 An example:
427 struct mtop mt_cmd;
429 mt_cmd.mt_op = MTSETDRVBUFFER;
430 mt_cmd.mt_count = MT_ST_BOOLEANS |
431 MT_ST_BUFFER_WRITES | MT_ST_ASYNC_WRITES;
432 ioctl(fd, MTIOCTOP, mt_cmd);
433 The default block size for a device can be set with
435 MT_ST_DEF_BLKSIZE and the default density code can be set with
436 MT_ST_DEFDENSITY. The values for the parameters are or'ed with
437 the operation code.
438 With kernels 2.1.x and later, the timeout values can be set
440 with the subcommand MT_ST_SET_TIMEOUT ORed with the timeout in
441 seconds. The long timeout (used for rewinds and other commands
442 that may take a long time) can be set with MT_ST_SET_LONG_TIME‐
443 OUT. The kernel defaults are very long to make sure that a
444 successful command is not timed out with any drive. Because of
445 this the driver may seem stuck even if it is only waiting for
446 the timeout. These commands can be used to set more practical
447 values for a specific drive. The timeouts set for one device
448 apply for all devices linked to the same drive.
449 Starting from kernels 2.4.19 and 2.5.43, the driver supports a
451 status bit which indicates whether the drive requests cleaning.
452 The method used by the drive to return cleaning information is
453 set using the MT_ST_SEL_CLN subcommand. If the value is zero,
454 the cleaning bit is always zero. If the value is one, the
455 TapeAlert data defined in the SCSI-3 standard is used (not yet
456 implemented). Values 2-17 are reserved. If the lowest eight
457 bits are >= 18, bits from the extended sense data are used.
458 The bits 9-16 specify a mask to select the bits to look at and
459 the bits 17-23 specify the bit pattern to look for. If the bit
460 pattern is zero, one or more bits under the mask indicate the
461 cleaning request. If the pattern is nonzero, the pattern must
462 match the masked sense data byte.
463 MTIOCGET — Get status
465 This request takes an argument of type (struct mtget *).
466 /* structure for MTIOCGET - mag tape get status command */
468 struct mtget {
469 long mt_type;
470 long mt_resid;
471 /* the following registers are device dependent */
472 long mt_dsreg;
473 long mt_gstat;
474 long mt_erreg;
475 /* The next two fields are not always used */
476 daddr_t mt_fileno;
477 daddr_t mt_blkno;
478 };
479 mt_type The header file defines many values for mt_type, but the
481 current driver reports only the generic types MT_ISSCSI1
482 (Generic SCSI-1 tape) and MT_ISSCSI2 (Generic SCSI-2 tape).
483 mt_resid contains the current tape partition number.
485 mt_dsreg reports the drive's current settings for block size (in the
487 low 24 bits) and density (in the high 8 bits). These fields
488 are defined by MT_ST_BLKSIZE_SHIFT, MT_ST_BLKSIZE_MASK,
489 MT_ST_DENSITY_SHIFT, and MT_ST_DENSITY_MASK.
490 mt_gstat reports generic (device independent) status information.
492 The header file defines macros for testing these status
493 bits:
494 GMT_EOF(x): The tape is positioned just after a filemark
496 (always false after an MTSEEK operation).
497 GMT_BOT(x): The tape is positioned at the beginning of the
499 first file (always false after an MTSEEK operation).
500 GMT_EOT(x): A tape operation has reached the physical End Of
502 Tape.
503 GMT_SM(x): The tape is currently positioned at a setmark
505 (always false after an MTSEEK operation).
506 GMT_EOD(x): The tape is positioned at the end of recorded
508 data.
509 GMT_WR_PROT(x): The drive is write-protected. For some
511 drives this can also mean that the drive does not sup‐
512 port writing on the current medium type.
513 GMT_ONLINE(x): The last open(2) found the drive with a tape
515 in place and ready for operation.
516 GMT_D_6250(x), GMT_D_1600(x), GMT_D_800(x): This “generic”
518 status information reports the current density setting
519 for 9-track ½" tape drives only.
520 GMT_DR_OPEN(x): The drive does not have a tape in place.
522 GMT_IM_REP_EN(x): Immediate report mode. This bit is set if
524 there are no guarantees that the data has been physi‐
525 cally written to the tape when the write call returns.
526 It is set zero only when the driver does not buffer data
527 and the drive is set not to buffer data.
528 GMT_CLN(x): The drive has requested cleaning. Implemented
530 in kernels since 2.4.19 and 2.5.43.
531 mt_erreg The only field defined in mt_erreg is the recovered error
533 count in the low 16 bits (as defined by MT_ST_SOFTERR_SHIFT
534 and MT_ST_SOFTERR_MASK. Due to inconsistencies in the way
535 drives report recovered errors, this count is often not
536 maintained (most drives do not by default report soft errors
537 but this can be changed with a SCSI MODE SELECT command).
538 mt_fileno reports the current file number (zero-based). This value is
540 set to -1 when the file number is unknown (e.g., after MTBSS
541 or MTSEEK).
542 mt_blkno reports the block number (zero-based) within the current
544 file. This value is set to -1 when the block number is
545 unknown (e.g., after MTBSF, MTBSS, or MTSEEK).
546 MTIOCPOS — Get tape position
548 This request takes an argument of type (struct mtpos *) and reports the
549 drive's notion of the current tape block number, which is not the same
550 as mt_blkno returned by MTIOCGET. This drive must be a SCSI-2 drive
551 that supports the READ POSITION command (device-specific address) or a
552 Tandberg-compatible SCSI-1 drive (Tandberg, Archive Viper, Wangtek, ...
553 ).
554 /* structure for MTIOCPOS - mag tape get position command */
556 struct mtpos {
557 long mt_blkno; /* current block number */
558 };
559
561 EACCES An attempt was made to write or erase a write-pro‐
562 tected tape. (This error is not detected during
563 open(2).)
564 EBUSY The device is already in use or the driver was
566 unable to allocate a buffer.
567 EFAULT The command parameters point to memory not belong‐
569 ing to the calling process.
570 EINVAL An ioctl(2) had an invalid argument, or a
572 requested block size was invalid.
573 EIO The requested operation could not be completed.
575 ENOMEM The byte count in read(2) is smaller than the next
577 physical block on the tape. (Before 2.2.18 and
578 2.4.0-test6 the extra bytes have been silently
579 ignored.)
580 ENOSPC A write operation could not be completed because
582 the tape reached end-of-medium.
583 ENOSYS Unknown ioctl(2).
585 ENXIO During opening, the tape device does not exist.
587 EOVERFLOW An attempt was made to read or write a variable-
589 length block that is larger than the driver's
590 internal buffer.
591 EROFS Open is attempted with O_WRONLY or O_RDWR when the
593 tape in the drive is write-protected.
594
596 /dev/st* the auto-rewind SCSI tape devices
597 /dev/nst* the nonrewind SCSI tape devices
599
601 1. When exchanging data between systems, both systems have to
602 agree on the physical tape block size. The parameters of a
603 drive after startup are often not the ones most operating
604 systems use with these devices. Most systems use drives in
605 variable-block mode if the drive supports that mode. This
606 applies to most modern drives, including DATs, 8mm helical
607 scan drives, DLTs, etc. It may be advisable to use these
608 drives in variable-block mode also in Linux (i.e., use
609 MTSETBLK or MTSETDEFBLK at system startup to set the mode),
610 at least when exchanging data with a foreign system. The
611 drawback of this is that a fairly large tape block size has
612 to be used to get acceptable data transfer rates on the SCSI
613 bus.
614 2. Many programs (e.g., tar(1)) allow the user to specify the
616 blocking factor on the command line. Note that this deter‐
617 mines the physical block size on tape only in variable-block
618 mode.
619 3. In order to use SCSI tape drives, the basic SCSI driver, a
621 SCSI-adapter driver and the SCSI tape driver must be either
622 configured into the kernel or loaded as modules. If the
623 SCSI-tape driver is not present, the drive is recognized but
624 the tape support described in this page is not available.
625 4. The driver writes error messages to the console/log. The
627 SENSE codes written into some messages are automatically
628 translated to text if verbose SCSI messages are enabled in
629 kernel configuration.
630 5. The driver's internal buffering allows good throughput in
632 fixed-block mode also with small read(2) and write(2) byte
633 counts. With direct transfers this is not possible and may
634 cause a surprise when moving to the 2.6 kernel. The solu‐
635 tion is to tell the software to use larger transfers (often
636 telling it to use larger blocks). If this is not possible,
637 direct transfers can be disabled.
638
640 mt(1)
641 The file drivers/scsi/README.st or Documentation/scsi/st.txt
643 (kernel >= 2.6) in the kernel sources contains the most recent
644 information about the driver and its configuration possibili‐
645 ties.
646
648 This page is part of release 3.25 of the Linux man-pages
649 project. A description of the project, and information about
650 reporting bugs, can be found at http://www.kernel.org/doc/man-
651 pages/.
652Linux 2007-12-16 ST(4)