Lines Matching +full:write +full:- +full:to +full:- +full:read

15 .\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
19 .\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
39 devices of the sequential access class that are attached to the system
62 The tape can be unmounted, bringing the session to a
65 .Bl -enum
68 referred to as sub-mode 00 below.
83 access is only sought when needed (e.g., to set parameters).
84 .Sh SUB-MODES
85 The sub-modes differ in the action taken when the device is closed:
86 .Bl -tag -width XXXX
93 If the tape was written to, a file mark will be written.
96 last read, or the written file mark.
110 block-size modes.
112 .Tn QIC Ns -type
113 devices run in fixed block-size mode, where most nine-track tapes and
114 many new cartridge formats allow variable block-size.
116 .Bl -inset
117 .It Variable block-size:
118 Each write made to the device results in a single logical record
119 written to the tape.
120 One can never read or write
122 of a record from tape (though you may request a larger block and read
123 a smaller record); nor can one read multiple blocks.
124 Data from a single write is therefore read by a single read.
132 logically considered to be immediately after the last item read,
135 but it was never read, then the next
136 process to read will immediately hit the file mark and receive an end-of-file notification.
137 .It Fixed block-size:
138 Data written by the user is passed to the tape as a succession of
141 considered to be a series of independent blocks.
142 One may never write
144 One may read and write the same data as a different set of records.
145 In other words, blocks that were written together may be read separately,
146 and vice-versa.
150 As there is some data to return (unless
151 there were no records before the file mark), the read will succeed,
153 The next read will return immediately with a value
155 (As above, if the file mark is never read, it remains for the next
156 process to read if in no-rewind mode.)
159 By default, the driver will NOT accept reads or writes to a tape device that
160 are larger than may be written to or read from the mounted tape using a single
161 write or read request.
163 are respected in terms of the block size written to tape.
164 For example, if the user tries to write a 256KB block to the tape, but the
165 controller can handle no more than 128KB, the write will fail.
168 behavior, prior to
171 was to break up large reads or writes into smaller blocks when going to the
173 The problem with that behavior, though, is that it hides the actual on-tape
181 .Bl -tag -width 12
184 This variable, when set to 1, will configure all
186 devices to split large buffers into smaller pieces when needed.
189 This variable, when set to 1, will configure the given
191 unit to split large buffers into multiple pieces.
197 variables available to view block handling parameters:
198 .Bl -tag -width 12
201 This variable allows the user to see, but not modify, the current I/O split
203 The user is not permitted to modify this setting so that there is no chance
209 capabilities of the controller that is attached to the tape drive.
214 READ BLOCK LIMITS command.
223 The handling of file marks on write is automatic.
225 written to the tape, and has not done a read since the last write,
226 then a file mark will be written to the tape when the device is
228 If a rewind is requested after a write, then the driver
230 that there are two file marks written to the tape.
231 The exception to
232 this is that there seems to be a standard (which we follow, but do not
233 understand why) that certain types of tape do not actually write two
234 file marks to tape, but when read, report a `phantom' file mark when the
235 last file is read.
246 .Dq mt param -l
250 .Dq mt param -s
261 .Bl -tag -width 5n
264 When set to 1, it sets the Suppress Incorrect Length Indicator (SILI) bit
270 See the SSC-5 spec (available at t10.org), specifically the section on the
271 READ(6) command, for more information.
277 of Media conditions by returning a write with 0 bytes written, and
279 set to 0.
282 is set to 1, the
290 This is a read-only parameter, and is set to 1 if the tape drive supports
293 If protection is supported, set this to the desired protection method
295 As of SSC-5r03 (available at t10.org), the protection method values are:
296 .Bl -tag -width 3n
300 Reed-Solomon CRC, 4 bytes in length.
307 If set to 1, enable logical block protection on writes.
308 The CRC must be appended to the end of the block written to the tape driver.
311 If set to 1, enable logical block protection on reads.
312 The CRC will be appended to the end of the block read from the tape driver.
315 If set to 1, enable logical block protection on the RECOVER BUFFERED DATA
325 driver has a set of default timeouts for SCSI commands (READ, WRITE, TEST UNIT
328 For newer tape drives that claim to support the SPC-4
331 driver will attempt to use the REPORT SUPPORTED OPERATION CODES command to
350 subcommand) it is generally best to use those values.
364 To set timeouts after boot, the per-instance timeout values, for example:
365 .Va kern.cam.sa.0.timeout.read ,
368 If a tape drive arrives after boot, the global tunables or per-instance
369 tunables that apply to the newly arrived drive will be used.
373 .Bl -tag -compact
379 .It kern.cam.sa.timeout.read
387 .It kern.cam.sa.timeout.write
395 .Bl -tag -compact
401 .It kern.cam.sa.%d.timeout.read
409 .It kern.cam.sa.%d.timeout.write
415 of a second, so be sure to account for that when setting them.
422 .Bl -tag -width /dev/[n][e]sa[0-9] -compact
423 .It Pa /dev/[n][e]sa[0-9]
432 Control mode device (to examine state while another program is
438 driver supports injecting End Of Media (EOM) notification to aid
440 EOM is indicated to the application by returning the read or write with 0
453 sysctl variable to 1.
455 query, and then the driver state will be reset to normal.
461 .An -nosplit
484 This driver lacks many of the hacks required to deal with older devices.
486 .Tn SCSI-1
493 are not automatically read correctly with this driver: you may need to
494 explicitly set variable block mode or set to the blocksize that works best
495 for your device in order to read tapes written under
500 It would be nice to add support for creating and editing tape partitions.