Documentation/scsi/st.rst

1 .. SPDX-License-Identifier: GPL-2.0
23 flexible method and applicable to single-user workstations. However,
32 drive performs auto-detection of the tape format well (like some
33 QIC-drives). The result is that any tape can be read, writing can be
37 does not perform auto-detection well enough and there is a single
40 or not :-).
57 between formats in multi-tape operations (the explicitly overridden
72 limits). Both the auto-rewind (minor equals device number) and
73 non-rewind devices (minor is 128 + device number) are implemented.
128     dev_upper non-rew mode dev-lower
129     20 -  8     7    6 5  4      0
131 The non-rewind bit is always bit 7 (the uppermost bit in the lowermost
132 byte). The bits defining the mode are below the non-rewind bit. The
143 and non-rewind entries for each mode. The names are stxy and nstxy, where x
151 the defaults set by the user. The value -1 means the default is not set. The
166 directory corresponding to the mode 0 auto-rewind device (e.g., st0).
179    regular expression "^st[0-9]+$"
191       - The number of I/Os currently outstanding to this device.
193       - The amount of time spent waiting (in nanoseconds) for all I/O
198       - The number of I/Os issued to the tape drive other than read or
200         following calculation io_ms-read_ms-write_ms.
202       - The number of bytes read from the tape drive.
204       - The number of read requests issued to the tape drive.
206       - The amount of time (in nanoseconds) spent waiting for read
209       - The number of bytes written to the tape drive.
211       - The number of write requests issued to the tape drive.
213       - The amount of time (in nanoseconds) spent waiting for write
216       - The number of times during a read or write we found
217 	the residual amount to be non-zero. This should mean that a program
257 is not possible, a driver buffer allocated at run-time is used. If
262 - one or more pages are at addresses not reachable by the HBA
263 - the number of pages in the transfer exceeds the number of
265 - one or more pages can't be locked into memory (should not happen in
273 allowed if ST_BUFFER_WRITES is non-zero and direct i/o is not used.
280 -b option) may have had good throughput but this is not true any more with
282 is to use bigger write() byte counts (e.g., tar -b 64).
291 tape after the early-warning mark to flush the driver buffer.
298 Scatter/gather buffers (buffers that consist of chunks non-contiguous
317    are used to extend the buffer at run-time if this is necessary. The
330 returns -1 and errno is set to ENOSPC. To enable writing a trailer,
332 bytes is returned. After this, -1 and the number of bytes are
349 			   tape drive if this is non-zero
353 set, the write threshold is set to the new buffer size - 2 kB.
368 the driver as module. If several parameters are set, the keyword-value
371 string st=. Here is an example::
381   - aa is the buffer size for fixed block mode in 1024 byte units
382   - bb is the write threshold in 1024 byte units
383   - dd is the maximum number of scatter/gather segments
393 (look for a package mt-st* from the Linux ftp sites; the GNU mt does
431 	Re-tension tape.
439 	Seek to tape block count. Uses Tandberg-compatible seek (QFA)
440         for SCSI-1 drives and SCSI-2 seek for SCSI-2 drives. The file and
474 	partitions (argument non-zero). If the argument is positive,
480 	LTO drives from LTO-5 upwards. The drive has to support partitions
524 		the MTSEEK and MTIOCPOS for SCSI-2 drives instead of
565 	   contains the new default. If the bits 8-15 are set to a
566 	   non-zero number, and this number is not 0xff, the number is
586 	   cleaning. The bits are device-dependent. The driver is
588 	   bits of the argument; must be >= 18 (values 1 - 17
590 	   a mask to select the relevant bits (the bits 9-16), and the
591 	   bit pattern (bits 17-23). If the bit pattern is zero, one
593 	   the pattern is non-zero, the pattern must match the masked
604         Tandberg-compatible QFA for SCSI-1 drives and the SCSI-2
605         command for the SCSI-2 drives.
612         block is -1 when it can't be determined (e.g., after MTBSF).
668 the driver is waiting. With the command 'ps -l' you can see the state