4 \chapter{Testing Your Tape Drive With Bacula}
5 \label{TapeTestingChapter}
6 \index[general]{Testing Your Tape Drive With Bacula}
8 This chapter is concerned with testing and configuring your tape drive to make
9 sure that it will work properly with Bacula using the {\bf btape} program.
12 \section{Get Your Tape Drive Working}
14 In general, you should follow the following steps to get your tape drive to
15 work with Bacula. Start with a tape mounted in your drive. If you have an
16 autochanger, load a tape into the drive. We use {\bf /dev/nst0} as the tape
17 drive name, you will need to adapt it according to your system.
19 Do not proceed to the next item until you have succeeded with the previous
23 \item Make sure that Bacula (the Storage daemon) is not running
24 or that you have {\bf unmount}ed the drive you will use
27 \item Use tar to write to, then read from your drive:
31 mt -f /dev/nst0 rewind
33 mt -f /dev/nst0 rewind
39 \item Make sure you have a valid and correct Device resource corresponding
40 to your drive. For Linux users, generally, the default one works. For
41 FreeBSD users, there are two possible Device configurations (see below).
42 For other drives and/or OSes, you will need to first ensure that your
43 system tape modes are properly setup (see below), then possibly modify
44 you Device resource depending on the output from the btape program (next
45 item). When doing this, you should consult the \ilink{Storage Daemon
46 Configuration}{StoredConfChapter} of this manual.
48 \item If you are using a Fibre Channel to connect your tape drive to
49 Bacula, please be sure to disable any caching in the NSR (network
50 storage router, which is a Fibre Channel to SCSI converter).
52 \item Run the btape {\bf test} command:
56 ./btape -c bacula-sd.conf /dev/nst0
62 It isn't necessary to run the autochanger part of the test at this time,
63 but do not go past this point until the basic test succeeds. If you do
64 have an autochanger, please be sure to read the \ilink{Autochanger
65 chapter}{AutochangersChapter} of this manual.
67 \item Run the btape {\bf fill} command, preferably with two volumes. This
68 can take a long time. If you have an autochanger and it is configured, Bacula
69 will automatically use it. If you do not have it configured, you can manually
70 issue the appropriate {\bf mtx} command, or press the autochanger buttons to
71 change the tape when requested to do so.
73 \item FreeBSD users, if you have a pre-5.0 system run the {\bf tapetest}
74 program, and make sure your system is patched if necessary. The tapetest
75 program can be found in the platform/freebsd directory. The instructions
76 for its use are at the top of the file.
78 \item Run Bacula, and backup a reasonably small directory, say 60
79 Megabytes. Do three successive backups of this directory.
81 \item Stop Bacula, then restart it. Do another full backup of the same
82 directory. Then stop and restart Bacula.
84 \item Do a restore of the directory backed up, by entering the following
85 restore command, being careful to restore it to an alternate location:
90 restore select all done
96 Do a {\bf diff} on the restored directory to ensure it is identical to the
97 original directory. If you are going to backup multiple different systems
98 (Linux, Windows, Mac, Solaris, FreeBSD, ...), be sure you test the restore
101 \item If you have an autochanger, you should now go back to the btape program
102 and run the autochanger test:
106 ./btape -c bacula-sd.conf /dev/nst0
112 Adjust your autochanger as necessary to ensure that it works correctly. See
113 the Autochanger chapter of this manual for a complete discussion of testing
116 \item We strongly recommend that you use a dedicated SCSI
117 controller for your tape drives. Scanners are known to induce
118 serious problems with the SCSI bus, causing it to reset. If the
119 SCSI bus is reset while Bacula has the tape drive open, it will
120 most likely be fatal to your tape since the drive will rewind.
121 These kinds of problems show up in the system log. For example,
122 the following was most likely caused by a scanner:
126 Feb 14 17:29:55 epohost kernel: (scsi0:A:2:0): No or incomplete CDB sent to device.
127 Feb 14 17:29:55 epohost kernel: scsi0: Issued Channel A Bus Reset. 1 SCBs aborted
133 If you have reached this point, you stand a good chance of having everything
134 work. If you get into trouble at any point, {\bf carefully} read the
135 documentation given below. If you cannot get past some point, ask the {\bf
136 bacula-users} email list, but specify which of the steps you have successfully
137 completed. In particular, you may want to look at the
138 \ilink{ Tips for Resolving Problems}{problems1} section below.
141 \label{NoTapeInDrive}
142 \subsection{Problems When no Tape in Drive}
143 \index[general]{Problems When no Tape in Drive}
144 When Bacula was first written the Linux 2.4 kernel permitted opening the
145 drive whether or not there was a tape in the drive. Thus the Bacula code is
146 based on the concept that if the drive cannot be opened, there is a serious
147 problem, and the job is failed.
149 With version 2.6 of the Linux kernel, if there is no tape in the drive, the
150 OS will wait two minutes (default) and then return a failure, and consequently,
151 Bacula version 1.36 and below will fail the job. This is important to keep
152 in mind, because if you use an option such as {\bf Offline on Unmount =
153 yes}, there will be a point when there is no tape in the drive, and if
154 another job starts or if Bacula asks the operator to mount a tape, when
155 Bacula attempts to open the drive (about a 20 minute delay), it will fail
156 and Bacula will fail the job.
158 In version 1.38.x, the Bacula code partially gets around this problem -- at
159 least in the initial open of the drive. However, functions like Polling
160 the drive do not work correctly if there is no tape in the drive.
161 Providing you do not use {\bf Offline on Unmount = yes}, you should not
162 experience job failures as mentioned above. If you do experience such
163 failures, you can also increase the {\bf Maximum Open Wait} time interval,
164 which will give you more time to mount the next tape before the job is
167 \subsection{Specifying the Configuration File}
168 \index[general]{File!Specifying the Configuration}
169 \index[general]{Specifying the Configuration File}
171 Starting with version 1.27, each of the tape utility programs including the
172 {\bf btape} program requires a valid Storage daemon configuration file
173 (actually, the only part of the configuration file that {\bf btape} needs is
174 the {\bf Device} resource definitions). This permits {\bf btape} to find the
175 configuration parameters for your archive device (generally a tape drive).
176 Without those parameters, the testing and utility programs do not know how to
177 properly read and write your drive. By default, they use {\bf bacula-sd.conf}
178 in the current directory, but you may specify a different configuration file
179 using the {\bf -c} option.
181 \subsection{Specifying a Device Name For a Tape}
182 \index[general]{Tape!Specifying a Device Name For a}
183 \index[general]{Specifying a Device Name For a Tape}
185 {\bf btape} {\bf device-name} where the Volume can be found. In the case of a
186 tape, this is the physical device name such as {\bf /dev/nst0} or {\bf
187 /dev/rmt/0ubn} depending on your system that you specify on the Archive Device
188 directive. For the program to work, it must find the identical name in the
189 Device resource of the configuration file. If the name is not found in the
190 list of physical names, the utility program will compare the name you entered
191 to the Device names (rather than the Archive device names).
193 When specifying a tape device, it is preferable that the "non-rewind"
194 variant of the device file name be given. In addition, on systems such as
195 Sun, which have multiple tape access methods, you must be sure to specify
196 to use Berkeley I/O conventions with the device. The
197 {\bf b} in the Solaris (Sun) archive specification {\bf /dev/rmt/0mbn} is
198 what is needed in this case. Bacula does not support SysV tape drive
201 See below for specifying Volume names.
203 \subsection{Specifying a Device Name For a File}
204 \index[general]{File!Specifying a Device Name For a}
205 \index[general]{Specifying a Device Name For a File}
207 If you are attempting to read or write an archive file rather than a tape, the
208 {\bf device-name} should be the full path to the archive location including
209 the filename. The filename (last part of the specification) will be stripped
210 and used as the Volume name, and the path (first part before the filename)
211 must have the same entry in the configuration file. So, the path is equivalent
212 to the archive device name, and the filename is equivalent to the volume name.
217 \index[general]{Btape}
219 This program permits a number of elementary tape operations via a tty command
220 interface. The {\bf test} command, described below, can be very useful for
221 testing tape drive compatibility problems. Aside from initial testing of tape
222 drive compatibility with {\bf Bacula}, {\bf btape} will be mostly used by
223 developers writing new tape drivers.
225 {\bf btape} can be dangerous to use with existing {\bf Bacula} tapes because
226 it will relabel a tape or write on the tape if so requested regardless of
227 whether or not the tape contains valuable data, so please be careful and use
228 it only on blank tapes.
230 To work properly, {\bf btape} needs to read the Storage daemon's configuration
231 file. As a default, it will look for {\bf bacula-sd.conf} in the current
232 directory. If your configuration file is elsewhere, please use the {\bf -c}
233 option to specify where.
235 The physical device name or the Device resource name must be specified on the
236 command line, and this same device name must be present in the Storage
237 daemon's configuration file read by {\bf btape}
241 Usage: btape [options] device_name
242 -b <file> specify bootstrap file
243 -c <file> set configuration file to file
244 -d <nn> set debug level to nn
245 -p proceed inspite of I/O errors
248 -? print this message.
252 \subsection{Using btape to Verify your Tape Drive}
253 \index[general]{Using btape to Verify your Tape Drive}
254 \index[general]{Drive!Using btape to Verify your Tape}
256 An important reason for this program is to ensure that a Storage daemon
257 configuration file is defined so that Bacula will correctly read and write
260 It is highly recommended that you run the {\bf test} command before running
261 your first Bacula job to ensure that the parameters you have defined for your
262 storage device (tape drive) will permit {\bf Bacula} to function properly. You
263 only need to mount a blank tape, enter the command, and the output should be
264 reasonably self explanatory. For example:
268 (ensure that Bacula is not running)
269 ./btape -c /usr/bin/bacula/bacula-sd.conf /dev/nst0
277 Tape block granularity is 1024 bytes.
278 btape: btape.c:376 Using device: /dev/nst0
283 Enter the test command:
291 The output produced should be something similar to the following: I've cut the
292 listing short because it is frequently updated to have new tests.
296 === Append files test ===
297 This test is essential to Bacula.
298 I'm going to write one record in file 0,
299 two records in file 1,
300 and three records in file 2
301 btape: btape.c:387 Rewound /dev/nst0
302 btape: btape.c:855 Wrote one record of 64412 bytes.
303 btape: btape.c:857 Wrote block to device.
304 btape: btape.c:410 Wrote EOF to /dev/nst0
305 btape: btape.c:855 Wrote one record of 64412 bytes.
306 btape: btape.c:857 Wrote block to device.
307 btape: btape.c:855 Wrote one record of 64412 bytes.
308 btape: btape.c:857 Wrote block to device.
309 btape: btape.c:410 Wrote EOF to /dev/nst0
310 btape: btape.c:855 Wrote one record of 64412 bytes.
311 btape: btape.c:857 Wrote block to device.
312 btape: btape.c:855 Wrote one record of 64412 bytes.
313 btape: btape.c:857 Wrote block to device.
314 btape: btape.c:855 Wrote one record of 64412 bytes.
315 btape: btape.c:857 Wrote block to device.
316 btape: btape.c:410 Wrote EOF to /dev/nst0
317 btape: btape.c:387 Rewound /dev/nst0
318 btape: btape.c:693 Now moving to end of media.
319 btape: btape.c:427 Moved to end of media
320 We should be in file 3. I am at file 3. This is correct!
321 Now the important part, I am going to attempt to append to the tape.
323 === End Append files test ===
327 If you do not successfully complete the above test, please resolve the
328 problem(s) before attempting to use {\bf Bacula}. Depending on your tape
329 drive, the test may recommend that you add certain records to your
330 configuration. We strongly recommend that you do so and then re-run the above
331 test to insure it works the first time.
333 Some of the suggestions it provides for resolving the problems may or may not
334 be useful. If at all possible avoid using fixed blocking. If the test suddenly
335 starts to print a long series of:
345 then almost certainly, you are running your drive in fixed block mode rather
346 than variable block mode. See below for more help of resolving fix
347 versus variable block problems.
349 It is also possible that you have your drive
350 set in SysV tape drive mode. The drive must use BSD tape conventions.
351 See the section above on setting your {\bf Archive device} correctly.
353 For FreeBSD users, please see the notes below for doing further testing of
357 \subsection{Linux SCSI Tricks}
358 \index[general]{Tricks!Linux SCSI}
359 \index[general]{Linux SCSI Tricks}
361 You can find out what SCSI devices you have by doing:
373 [0:0:0:0] disk ATA ST3160812AS 3.AD /dev/sda
374 [2:0:4:0] tape HP Ultrium 2-SCSI F6CH /dev/st0
375 [2:0:5:0] tape HP Ultrium 2-SCSI F6CH /dev/st1
376 [2:0:6:0] mediumx OVERLAND LXB 0107 -
377 [2:0:9:0] tape HP Ultrium 1-SCSI E50H /dev/st2
378 [2:0:10:0] mediumx OVERLAND LXB 0107 -
382 There are two drives in one autochanger: /dev/st0 and /dev/st1
383 and a third tape drive at /dev/st2. For using them with Bacula, one
384 would normally reference them as /dev/nst0 ... /dev/nst2. Not also,
385 there are two different autochangers identified as "mediumx OVERLAND LXB".
386 They can be addressed via their /dev/sgN designation, which can be
387 obtained by counting from the beginning as 0 to each changer. In the
388 above case, the two changers are located on /dev/sg3 and /dev/sg5. The one
389 at /dev/sg3, controls drives /dev/nst0 and /dev/nst1; and the one at
390 /dev/sg5 controles drive /dev/nst2.
392 If you do not have the {\bf lsscsi} command, you can obtain the same
393 information as follows:
401 For the above example with the three drives and two autochangers,
407 Host: scsi0 Channel: 00 Id: 00 Lun: 00
408 Vendor: ATA Model: ST3160812AS Rev: 3.AD
409 Type: Direct-Access ANSI SCSI revision: 05
410 Host: scsi2 Channel: 00 Id: 04 Lun: 00
411 Vendor: HP Model: Ultrium 2-SCSI Rev: F6CH
412 Type: Sequential-Access ANSI SCSI revision: 03
413 Host: scsi2 Channel: 00 Id: 05 Lun: 00
414 Vendor: HP Model: Ultrium 2-SCSI Rev: F6CH
415 Type: Sequential-Access ANSI SCSI revision: 03
416 Host: scsi2 Channel: 00 Id: 06 Lun: 00
417 Vendor: OVERLAND Model: LXB Rev: 0107
418 Type: Medium Changer ANSI SCSI revision: 02
419 Host: scsi2 Channel: 00 Id: 09 Lun: 00
420 Vendor: HP Model: Ultrium 1-SCSI Rev: E50H
421 Type: Sequential-Access ANSI SCSI revision: 03
422 Host: scsi2 Channel: 00 Id: 10 Lun: 00
423 Vendor: OVERLAND Model: LXB Rev: 0107
424 Type: Medium Changer ANSI SCSI revision: 02
429 As an additional example, I get the following (on a different machine from the
435 Host: scsi2 Channel: 00 Id: 01 Lun: 00
436 Vendor: HP Model: C5713A Rev: H107
437 Type: Sequential-Access ANSI SCSI revision: 02
438 Host: scsi2 Channel: 00 Id: 04 Lun: 00
439 Vendor: SONY Model: SDT-10000 Rev: 0110
440 Type: Sequential-Access ANSI SCSI revision: 02
444 The above represents first an autochanger and second a simple
445 tape drive. The HP changer (the first entry) uses the same SCSI channel
446 for data and for control, so in Bacula, you would use:
449 Archive Device = /dev/nst0
450 Changer Device = /dev/sg0
454 If you want to remove the SDT-10000 device, you can do so as root with:
458 echo "scsi remove-single-device 2 0 4 0">/proc/scsi/scsi
462 and you can put add it back with:
466 echo "scsi add-single-device 2 0 4 0">/proc/scsi/scsi
470 where the 2 0 4 0 are the Host, Channel, Id, and Lun as seen on the output
471 from {\bf cat /proc/scsi/scsi}. Note, the Channel must be specified as
474 Below is a slightly more complicated output, which is a single autochanger
475 with two drives, and which operates the changer on a different channel
476 from from the drives:
481 Host: scsi0 Channel: 00 Id: 00 Lun: 00
482 Vendor: ATA Model: WDC WD1600JD-75H Rev: 08.0
483 Type: Direct-Access ANSI SCSI revision: 05
484 Host: scsi2 Channel: 00 Id: 04 Lun: 00
485 Vendor: HP Model: Ultrium 2-SCSI Rev: F6CH
486 Type: Sequential-Access ANSI SCSI revision: 03
487 Host: scsi2 Channel: 00 Id: 05 Lun: 00
488 Vendor: HP Model: Ultrium 2-SCSI Rev: F6CH
489 Type: Sequential-Access ANSI SCSI revision: 03
490 Host: scsi2 Channel: 00 Id: 06 Lun: 00
491 Vendor: OVERLAND Model: LXB Rev: 0106
492 Type: Medium Changer ANSI SCSI revision: 02
496 The above tape drives are accessed on /dev/nst0 and /dev/nst1, while
497 the control channel for those two drives is /dev/sg3.
502 \section{Tips for Resolving Problems}
503 \index[general]{Problems!Tips for Resolving}
504 \index[general]{Tips for Resolving Problems}
506 \label{CannotRestore}
507 \subsection{Bacula Saves But Cannot Restore Files}
508 \index[general]{Files!Bacula Saves But Cannot Restore}
509 \index[general]{Bacula Saves But Cannot Restore Files}
511 If you are getting error messages such as:
515 Volume data error at 0:1! Wanted block-id: "BB02", got "". Buffer discarded
519 It is very likely that Bacula has tried to do block positioning and ended up
520 at an invalid block. This can happen if your tape drive is in fixed block mode
521 while Bacula's default is variable blocks. Note that in such cases, Bacula is
522 perfectly able to write to your Volumes (tapes), but cannot position to read
525 There are two possible solutions.
528 \item The first and best is to always ensure that your drive is in variable
529 block mode. Note, it can switch back to fixed block mode on a reboot or if
530 another program uses the drive. So on such systems you need to modify the
531 Bacula startup files to explicitly set:
535 mt -f /dev/nst0 defblksize 0
539 or whatever is appropriate on your system. Note, if you are running a Linux
540 system, and the above command does not work, it is most likely because you
541 have not loaded the appropriate {\bf mt} package, which is often called
542 {\bf mt\_st}, but may differ according to your distribution.
544 \item The second possibility, especially, if Bacula wrote while the drive was
545 in fixed block mode, is to turn off block positioning in Bacula. This is done
550 Block Positioning = no
554 to the Device resource. This is not the recommended procedure because it can
555 enormously slow down recovery of files, but it may help where all else
556 fails. This directive is available in version 1.35.5 or later (and not yet
560 If you are getting error messages such as:
563 Volume data error at 0:0!
564 Block checksum mismatch in block=0 len=32625 calc=345678 blk=123456
568 You are getting tape read errors, and this is most likely due to
569 one of the following things:
571 \item An old or bad tape.
572 \item A dirty drive that needs cleaning (particularly for DDS drives).
573 \item A loose SCSI cable.
574 \item Old firmware in your drive. Make sure you have the latest firmware
576 \item Computer memory errors.
577 \item Over-clocking your CPU.
578 \item A bad SCSI card.
583 \subsection{Bacula Cannot Open the Device}
584 \index[general]{Device!Bacula Cannot Open the}
585 \index[general]{Bacula Cannot Open the Device}
587 If you get an error message such as:
591 dev open failed: dev.c:265 stored: unable to open
592 device /dev/nst0:> ERR=No such device or address
596 the first time you run a job, it is most likely due to the fact that you
597 specified the incorrect device name on your {\bf Archive Device}.
599 If Bacula works fine with your drive, then all off a sudden you get error
600 messages similar to the one shown above, it is quite possible that your driver
601 module is being removed because the kernel deems it idle. This is done via
602 {\bf crontab} with the use of {\bf rmmod -a}. To fix the problem, you can
603 remove this entry from {\bf crontab}, or you can manually {\bf modprob} your
604 driver module (or add it to the local startup script). Thanks to Alan Brown
606 \label{IncorrectFiles}
608 \subsection{Incorrect File Number}
609 \index[general]{Number!Incorrect File}
610 \index[general]{Incorrect File Number}
612 When Bacula moves to the end of the medium, it normally uses the {\bf
613 ioctl(MTEOM)} function. Then Bacula uses the {\bf ioctl(MTIOCGET)} function to
614 retrieve the current file position from the {\bf mt\_fileno} field. Some SCSI
615 tape drivers will use a fast means of seeking to the end of the medium and in
616 doing so, they will not know the current file position and hence return a {\bf
617 -1}. As a consequence, if you get {\bf "This is NOT correct!"} in the
618 positioning tests, this may be the cause. You must correct this condition in
619 order for Bacula to work.
621 There are two possible solutions to the above problem of incorrect file
625 \item Figure out how to configure your SCSI driver to keep track of the file
626 position during the MTEOM request. This is the preferred solution.
627 \item Modify the {\bf Device} resource of your {\bf bacula-sd.conf} file to
632 Hardware End of File = no
636 This will cause Bacula to use the MTFSF request to seek to the end of the
637 medium, and Bacula will keep track of the file number itself.
640 \label{IncorrectBlocks}
641 \subsection{Incorrect Number of Blocks or Positioning Errors}
642 \index[general]{Testing!Incorrect Number of Blocks or Positioning Errors}
643 \index[general]{Incorrect Number of Blocks or Positioning Errors}
645 {\bf Bacula's} preferred method of working with tape drives (sequential
646 devices) is to run in variable block mode, and this is what is set by default.
647 You should first ensure that your tape drive is set for variable block mode
650 If your tape drive is in fixed block mode and you have told Bacula to use
651 different fixed block sizes or variable block sizes (default), you will get
652 errors when Bacula attempts to forward space to the correct block (the kernel
653 driver's idea of tape blocks will not correspond to Bacula's).
655 All modern tape drives support variable tape blocks, but some older drives (in
656 particular the QIC drives) as well as the ATAPI ide-scsi driver run only in
657 fixed block mode. The Travan tape drives also apparently must run in fixed
658 block mode (to be confirmed).
660 Even in variable block mode, with the exception of the first record on the
661 second or subsequent volume of a multi-volume backup, Bacula will write blocks
662 of a fixed size. However, in reading a tape, Bacula will assume that for each
663 read request, exactly one block from the tape will be transferred. This the
664 most common way that tape drives work and is well supported by {\bf Bacula}.
666 Drives that run in fixed block mode can cause serious problems for Bacula if
667 the drive's block size does not correspond exactly to {\bf Bacula's} block
668 size. In fixed block size mode, drivers may transmit a partial block or
669 multiple blocks for a single read request. From {\bf Bacula's} point of view,
670 this destroys the concept of tape blocks. It is much better to run in variable
671 block mode, and almost all modern drives (the OnStream is an exception) run in
672 variable block mode. In order for Bacula to run in fixed block mode, you must
673 include the following records in the Storage daemon's Device resource
678 Minimum Block Size = nnn
679 Maximum Block Size = nnn
683 where {\bf nnn} must be the same for both records and must be identical to the
684 driver's fixed block size.
686 We recommend that you avoid this configuration if at all possible by using
687 variable block sizes.
689 If you must run with fixed size blocks, make sure they are not 512 bytes. This
690 is too small and the overhead that Bacula has with each record will become
691 excessive. If at all possible set any fixed block size to something like
692 64,512 bytes or possibly 32,768 if 64,512 is too large for your drive. See
693 below for the details on checking and setting the default drive block size.
695 To recover files from tapes written in fixed block mode, see below.
698 \subsection{Ensuring that the Tape Modes Are Properly Set -- {\bf Linux
700 \index[general]{Ensuring that the Tape Modes Are Properly Set -- Linux Only}
702 If you have a modern SCSI tape drive and you are having problems with the {\bf
703 test} command as noted above, it may be that some program has set one or more
704 of your SCSI driver's options to non-default values. For example, if your
705 driver is set to work in SysV manner, Bacula will not work correctly because
706 it expects BSD behavior. To reset your tape drive to the default values, you
707 can try the following, but {\bf ONLY} if you have a SCSI tape drive on a {\bf
713 mt -f /dev/nst0 rewind
714 mt -f /dev/nst0 stoptions buffer-writes async-writes read-ahead
718 The above commands will clear all options and then set those specified. None
719 of the specified options are required by Bacula, but a number of other options
720 such as SysV behavior must not be set. Bacula does not support SysV tape
721 behavior. On systems other than Linux, you will need to consult your {\bf mt}
722 man pages or documentation to figure out how to do the same thing. This should
723 not really be necessary though -- for example, on both Linux and Solaris
724 systems, the default tape driver options are compatible with Bacula.
725 On Solaris systems, you must take care to specify the correct device
726 name on the {\bf Archive device} directive. See above for more details.
728 You may also want to ensure that no prior program has set the default block
729 size, as happened to one user, by explicitly turning it off with:
733 mt -f /dev/nst0 defblksize 0
737 If you are running a Linux
738 system, and the above command does not work, it is most likely because you
739 have not loaded the appropriate {\bf mt} package, which is often called
740 {\bf mt\_st}, but may differ according to your distribution.
742 If you would like to know what options you have set before making any of the
743 changes noted above, you can now view them on Linux systems, thanks to a tip
744 provided by Willem Riede. Do the following:
749 mt -f /dev/nst0 stsetoptions 0
750 grep st0 /var/log/messages
754 and you will get output that looks something like the following:
758 kernel: st0: Mode 0 options: buffer writes: 1, async writes: 1, read ahead: 1
759 kernel: st0: can bsr: 0, two FMs: 0, fast mteom: 0, auto lock: 0,
760 kernel: st0: defs for wr: 0, no block limits: 0, partitions: 0, s2 log: 0
761 kernel: st0: sysv: 0 nowait: 0
765 Note, I have chopped off the beginning of the line with the date and machine
766 name for presentation purposes.
768 Some people find that the above settings only last until the next reboot, so
769 please check this otherwise you may have unexpected problems.
771 Beginning with Bacula version 1.35.8, if Bacula detects that you are running
772 in variable block mode, it will attempt to set your drive appropriately. All
773 OSes permit setting variable block mode, but some OSes do not permit setting
774 the other modes that Bacula needs to function properly.
777 \subsection{Tape Hardware Compression and Blocking Size}
778 \index[general]{Tape Hardware Compression and Blocking Size}
779 \index[general]{Size!Tape Hardware Compression and Blocking Size}
781 As far as I can tell, there is no way with the {\bf mt} program to check if
782 your tape hardware compression is turned on or off. You can, however, turn it
783 on by using (on Linux):
788 mt -f /dev/nst0 defcompression 1
792 and of course, if you use a zero instead of the one at the end, you will turn
795 If you have built the {\bf mtx} program in the {\bf depkgs} package, you can
796 use tapeinfo to get quite a bit of information about your tape drive even if
797 it is not an autochanger. This program is called using the SCSI control
798 device. On Linux for tape drive /dev/nst0, this is usually /dev/sg0, while on
799 FreeBSD for /dev/nsa0, the control device is often /dev/pass2. For example on
800 my DDS-4 drive (/dev/nst0), I get the following:
805 Product Type: Tape Drive
807 Product ID: 'C5713A '
816 Medium Type: Not Loaded
822 where the {\bf DataCompEnabled: yes} means that tape hardware compression is
823 turned on. You can turn it on and off (yes|no) by using the {\bf mt}
824 commands given above. Also, this output will tell you if the {\bf BlockSize}
825 is non-zero and hence set for a particular block size. Bacula is not likely to
826 work in such a situation because it will normally attempt to write blocks of
827 64,512 bytes, except the last block of the job which will generally be
828 shorter. The first thing to try is setting the default block size to zero
829 using the {\bf mt -f /dev/nst0 defblksize 0} command as shown above.
830 On FreeBSD, this would be something like: {\bf mt -f /dev/nsa0 blocksize 0}.
832 On some operating systems with some tape drives, the amount of data that
833 can be written to the tape and whether or not compression is enabled is
834 determined by the density usually the {\bf mt -f /dev/nst0 setdensity xxx} command.
835 Often {\bf mt -f /dev/nst0 status} will print out the current
836 density code that is used with the drive. Most systems, but unfortunately
837 not all, set the density to the maximum by default. On some systems, you
838 can also get a list of all available density codes with:
839 {\bf mt -f /dev/nst0 densities} or a similar {\bf mt} command.
840 Note, for DLT and SDLT devices, no-compression versus compression is very
841 often controlled by the density code. On FreeBSD systems, the compression
842 mode is set using {\bf mt -f /dev/nsa0 comp xxx} where xxx is the
843 mode you want. In general, see {\bf man mt} for the options available on
846 Note, some of the above {\bf mt} commands may not be persistent depending
847 on your system configuration. That is they may be reset if a program
848 other than Bacula uses the drive or, as is frequently the case, on reboot
851 If your tape drive requires fixed block sizes (very unusual), you can use the
856 Minimum Block Size = nnn
857 Maximum Block Size = nnn
861 in your Storage daemon's Device resource to force Bacula to write fixed size
862 blocks (where you sent nnn to be the same for both of the above records). This
863 should be done only if your drive does not support variable block sizes, or
864 you have some other strong reasons for using fixed block sizes. As mentioned
865 above, a small fixed block size of 512 or 1024 bytes will be very inefficient.
866 Try to set any fixed block size to something like 64,512 bytes or larger if
867 your drive will support it.
869 Also, note that the {\bf Medium Type} field of the output of {\bf tapeinfo}
870 reports {\bf Not Loaded}, which is not correct. As a consequence, you should
871 ignore that field as well as the {\bf Attached Changer} field.
873 To recover files from tapes written in fixed block mode, see below.
876 \subsection{Tape Modes on FreeBSD}
877 \index[general]{FreeBSD!Tape Modes on}
878 \index[general]{Tape Modes on FreeBSD}
880 On most FreeBSD systems such as 4.9 and most tape drives, Bacula should run
885 mt -f /dev/nsa0 seteotmodel 2
886 mt -f /dev/nsa0 blocksize 0
887 mt -f /dev/nsa0 comp enable
891 You might want to put those commands in a startup script to make sure your
892 tape driver is properly initialized before running Bacula, because
893 depending on your system configuration, these modes may be reset if a
894 program other than Bacula uses the drive or when your system is rebooted.
896 Then according to what the {\bf btape test} command returns, you will probably
897 need to set the following (see below for an alternative):
901 Hardware End of Medium = no
903 Backward Space Record = no
904 Backward Space File = no
905 Fast Forward Space File = no
910 Then be sure to run some append tests with Bacula where you start and stop
911 Bacula between appending to the tape, or use {\bf btape} version 1.35.1 or
912 greater, which includes simulation of stopping/restarting Bacula.
914 Please see the file {\bf platforms/freebsd/pthreads-fix.txt} in the main
915 Bacula directory concerning {\bf important} information concerning
916 compatibility of Bacula and your system. A much more optimal Device
917 configuration is shown below, but does not work with all tape drives. Please
918 test carefully before putting either into production.
920 Note, for FreeBSD 4.10-RELEASE, using a Sony TSL11000 L100 DDS4 with an
921 autochanger set to variable block size and DCLZ compression, Brian McDonald
922 reports that to get Bacula to append correctly between Bacula executions,
923 the correct values to use are:
927 mt -f /dev/nsa0 seteotmodel 1
928 mt -f /dev/nsa0 blocksize 0
929 mt -f /dev/nsa0 comp enable
937 Hardware End of Medium = no
939 Backward Space Record = no
940 Backward Space File = no
941 Fast Forward Space File = yes
946 This has been confirmed by several other people using different hardware. This
947 configuration is the preferred one because it uses one EOF and no backspacing
948 at the end of the tape, which works much more efficiently and reliably with
951 Finally, here is a Device configuration that Danny Butroyd reports to work
952 correctly with the Overland Powerloader tape library using LT0-2 and
957 # Overland Powerloader LT02 - 17 slots single drive
961 Archive Device = /dev/nsa0
962 AutomaticMount = yes;
964 RemovableMedia = yes;
966 Changer Command = "/usr/local/sbin/mtx-changer %c %o %S %a %d"
967 Changer Device = /dev/pass2
969 Alert Command = "sh -c 'tapeinfo -f %c |grep TapeAlert|cat'"
971 # FreeBSD Specific Settings
972 Offline On Unmount = no
973 Hardware End of Medium = no
975 Backward Space Record = no
976 Fast Forward Space File = no
980 The following Device resource works fine with Dell PowerVault 110T and
981 120T devices on both FreeBSD 5.3 and on NetBSD 3.0. It also works
982 with Sony AIT-2 drives on FreeBSD.
987 # FreeBSD/NetBSD Specific Settings
988 Hardware End of Medium = no
990 Backward Space Record = no
991 Fast Forward Space File = yes
997 On FreeBSD version 6.0, it is reported that you can even set
998 Backward Space Record = yes.
1002 \subsection{Finding your Tape Drives and Autochangers on FreeBSD}
1003 \index[general]{FreeBSD!Finding Tape Drives and Autochangers}
1004 \index[general]{Finding Tape Drives and Autochangers on FreeBSD}
1006 On FreeBSD, you can do a {\bf camcontrol devlist} as root to determine what
1007 drives and autochangers you have. For example,
1011 undef# camcontrol devlist
1012 at scbus0 target 2 lun 0 (pass0,sa0)
1013 at scbus0 target 4 lun 0 (pass1,sa1)
1014 at scbus0 target 4 lun 1 (pass2)
1018 from the above, you can determine that there is a tape drive on {\bf /dev/sa0}
1019 and another on {\bf /dev/sa1} in addition since there is a second line for the
1020 drive on {\bf /dev/sa1}, you know can assume that it is the control device for
1021 the autochanger (i.e. {\bf /dev/pass2}). It is also the control device name to
1022 use when invoking the tapeinfo program. E.g.
1026 tapeinfo -f /dev/pass2
1032 \subsection{Using the OnStream driver on Linux Systems}
1033 \index[general]{Using the OnStream driver on Linux Systems}
1034 \index[general]{Systems!Using the OnStream driver on Linux}
1036 Bacula version 1.33 (not 1.32x) is now working and ready for testing with the
1037 OnStream kernel osst driver version 0.9.14 or above. Osst is available from:
1038 \elink{http://sourceforge.net/projects/osst/}
1039 {http://sourceforge.net/projects/osst/}.
1041 To make Bacula work you must first load the new driver then, as root, do:
1045 mt -f /dev/nosst0 defblksize 32768
1049 Also you must add the following to your Device resource in your Storage
1054 Minimum Block Size = 32768
1055 Maximum Block Size = 32768
1059 Here is a Device specification provided by Michel Meyers that is known to
1065 Name = "Onstream DI-30"
1066 Media Type = "ADR-30"
1067 Archive Device = /dev/nosst0
1068 Minimum Block Size = 32768
1069 Maximum Block Size = 32768
1070 Hardware End of Medium = yes
1072 Backward Space File = yes
1073 Fast Forward Space File = yes
1075 AutomaticMount = yes
1077 Removable Media = yes
1082 \section{Hardware Compression on EXB-8900}
1083 \index[general]{Hardware Compression on EXB-8900}
1084 \index[general]{EXB-8900!Hardware Compression}
1086 To active, check, or disable the hardware compression feature
1087 on an EXB-8900, use the exabyte MammothTool. You can get it here:
1088 \elink{http://www.exabyte.com/support/online/downloads/index.cfm}
1089 {http://www.exabyte.com/support/online/downloads/index.cfm}.
1090 There is a Solaris version of this tool. With option -C 0 or 1 you
1091 can disable or activate compression. Start this tool without any
1092 options for a small reference.
1095 \subsection{Using btape to Simulate Filling a Tape}
1096 \index[general]{Using btape to Simulate Filling a Tape}
1097 \index[general]{Tape!Using btape to Simulate Filling}
1099 Because there are often problems with certain tape drives or systems when end
1100 of tape conditions occur, {\bf btape} has a special command {\bf fill} that
1101 causes it to write random data to a tape until the tape fills. It then writes
1102 at least one more Bacula block to a second tape. Finally, it reads back both
1103 tapes to ensure that the data has been written in a way that Bacula can
1104 recover it. Note, there is also a single tape option as noted below, which you
1105 should use rather than the two tape test. See below for more details.
1107 This can be an extremely time consuming process (here it is about 6 hours) to
1108 fill a full tape. Note, that btape writes random data to the tape when it is
1109 filling it. This has two consequences: 1. it takes a bit longer to generate
1110 the data, especially on slow CPUs. 2. the total amount of data is
1111 approximately the real physical capacity of your tape, regardless of whether
1112 or not the tape drive compression is on or off. This is because random data
1113 does not compress very much.
1115 To begin this test, you enter the {\bf fill} command and follow the
1116 instructions. There are two options: the simple single tape option and the
1117 multiple tape option. Please use only the simple single tape option because
1118 the multiple tape option still doesn't work totally correctly. If the single
1119 tape option does not succeed, you should correct the problem before using
1121 \label{RecoveringFiles}
1123 \section{Recovering Files Written With Fixed Block Sizes}
1124 \index[general]{Recovering Files Written With Fixed Block Sizes}
1126 If you have been previously running your tape drive in fixed block mode
1127 (default 512) and Bacula with variable blocks (default), then in version
1128 1.32f-x and 1.34 and above, Bacula will fail to recover files because it does
1129 block spacing, and because the block sizes don't agree between your tape drive
1130 and Bacula it will not work.
1132 The long term solution is to run your drive in variable block mode as
1133 described above. However, if you have written tapes using fixed block sizes,
1134 this can be a bit of a pain. The solution to the problem is: while you are
1135 doing a restore command using a tape written in fixed block size, ensure that
1136 your drive is set to the fixed block size used while the tape was written.
1137 Then when doing the {\bf restore} command in the Console program, do not
1138 answer the prompt {\bf yes/mod/no}. Instead, edit the bootstrap file (the
1139 location is listed in the prompt) using any ASCII editor. Remove all {\bf
1140 VolBlock} lines in the file. When the file is re-written, answer the question,
1141 and Bacula will run without using block positioning, and it should recover
1145 \section{Tape Blocking Modes}
1146 \index[general]{Modes!Tape Blocking}
1147 \index[general]{Tape Blocking Modes}
1149 SCSI tapes may either be written in {\bf variable} or {\bf fixed} block sizes.
1150 Newer drives support both modes, but some drives such as the QIC devices
1151 always use fixed block sizes. Bacula attempts to fill and write complete
1152 blocks (default 65K), so that in normal mode (variable block size), Bacula
1153 will always write blocks of the same size except the last block of a Job. If
1154 Bacula is configured to write fixed block sizes, it will pad the last block of
1155 the Job to the correct size. Bacula expects variable tape block size drives to
1156 behave as follows: Each write to the drive results in a single record being
1157 written to the tape. Each read returns a single record. If you request less
1158 bytes than are in the record, only those number of bytes will be returned, but
1159 the entire logical record will have been read (the next read will retrieve the
1160 next record). Thus data from a single write is always returned in a single
1161 read, and sequentially written records are returned by sequential reads.
1163 Bacula expects fixed block size tape drives to behave as follows: If a write
1164 length is greater than the physical block size of the drive, the write will be
1165 written as two blocks each of the fixed physical size. This single write may
1166 become multiple physical records on the tape. (This is not a good situation).
1167 According to the documentation, one may never write an amount of data that is
1168 not the exact multiple of the blocksize (it is not specified if an error
1169 occurs or if the the last record is padded). When reading, it is my
1170 understanding that each read request reads one physical record from the tape.
1171 Due to the complications of fixed block size tape drives, you should avoid
1172 them if possible with Bacula, or you must be ABSOLUTELY certain that you use
1173 fixed block sizes within Bacula that correspond to the physical block size of
1174 the tape drive. This will ensure that Bacula has a one to one correspondence
1175 between what it writes and the physical record on the tape.
1177 Please note that Bacula will not function correctly if it writes a block and
1178 that block is split into two or more physical records on the tape. Bacula
1179 assumes that each write causes a single record to be written, and that it can
1180 sequentially recover each of the blocks it has written by using the same
1181 number of sequential reads as it had written.
1183 \section{Details of Tape Modes}
1184 \index[general]{Modes!Details}
1185 \index[general]{Details of Tape Modes}
1186 Rudolf Cejka has provided the following information concerning
1187 certain tape modes and MTEOM.
1191 It is always possible to position filemarks or blocks, whereas
1192 positioning to the end-of-data is only optional feature, however it is
1193 implemented very often. SCSI specification also talks about optional
1194 sequential filemarks, setmarks and sequential setmarks, but these are not
1195 implemented so often. Modern tape drives keep track of file positions in
1196 built-in chip (AIT, LTO) or at the beginning of the tape (SDLT), so there
1197 is not any speed difference, if end-of-data or filemarks is used (I have
1198 heard, that LTO-1 from all 3 manufacturers do not use its chip for file
1199 locations, but a tape as in SDLT case, and I'm not sure about LTO-2 and
1200 LTO-3 case). However there is a big difference, that end-of-data ignores
1201 file position, whereas filemarks returns the real number of skipped
1202 files, so OS can track current file number just in filemarks case.
1205 Solaris does use just SCSI SPACE Filemarks, it does not support SCSI
1206 SPACE End-of-data. When MTEOM is called, Solaris does use SCSI SPACE
1207 Filemarks with count = 1048576 for fast mode, and combination of SCSI
1208 SPACE Filemarks with count = 1 with SCSI SPACE Blocks with count = 1 for
1209 slow mode, so EOD mark on the tape on some older tape drives is not
1210 skipped. File number is always tracked for MTEOM.
1212 Linux does support both SCSI SPACE Filemarks and End-of-data: When MTEOM
1213 is called in MT\_ST\_FAST\_MTEOM mode, SCSI SPACE End-of-data is used.
1214 In the other case, SCSI SPACE Filemarks with count =
1216 There is no real slow mode like in Solaris - I just expect, that for
1217 older tape drives Filemarks may be slower than End-of-data, but not so
1218 much as in Solaris slow mode. File number is tracked for MTEOM just
1219 without MT\_ST\_FAST\_MTEOM - when MT\_ST\_FAST\_MTEOM is used, it is not.
1221 FreeBSD does support both SCSI SPACE Filemarks and End-of-data, but when
1222 MTEOD (MTEOM) is called, SCSI SPACE End-of-data is always used. FreeBSD
1223 never use SCSI SPACE Filemarks for MTEOD. File number is never tracked
1227 When {\bf Hardware End of Medium = Yes} is used, MTEOM is called, but it
1228 does not mean, that hardware End-of-data must be used. When Hardware End
1229 of Medium = No, if Fast Forward Space File = Yes, MTFSF with count =
1230 32767 is used, else Block Read with count = 1 with Forward Space File
1231 with count = 1 is used, which is really very slow.
1233 \item [Hardware End of Medium = Yes|No]
1234 The name of this option is misleading and is the source of confusion,
1235 because it is not the hardware EOM, what is really switched here.
1237 If I use Yes, OS must not use SCSI SPACE End-of-data, because Bacula
1238 expects, that there is tracked file number, which is not supported by
1239 SCSI specification. Instead, the OS have to use SCSI SPACE Filemarks.
1241 If I use No, an action depends on Fast Forward Space File.
1243 When I set {\bf Hardware End of Medium = no}
1244 and {\bf Fast Forward Space File = no}
1245 file positioning was very slow
1246 on my LTO-3 (about ten to 100 minutes), but
1248 with {\bf Hardware End of Medium = no} and
1249 {\bf Fast Forward Space File = yes}, the time is ten to
1250 100 times faster (about one to two minutes).
1254 \section{Autochanger Errors}
1255 \index[general]{Errors!Autochanger}
1256 \index[general]{Autochanger Errors}
1258 If you are getting errors such as:
1262 3992 Bad autochanger "load slot 1, drive 1": ERR=Child exited with code 1.
1266 and you are running your Storage daemon as non-root, then most likely
1267 you are having permissions problems with the control channel. Running
1268 as root, set permissions on /dev/sgX so that the userid and group of
1269 your Storage daemon can access the device. You need to ensure that you
1270 all access to the proper control device, and if you don't have any
1271 SCSI disk drives (including SATA drives), you might want to change
1272 the permissions on /dev/sg*.
1274 \section{Syslog Errors}
1275 \index[general]{Errors!Syslog}
1276 \index[general]{Syslog Errors}
1278 If you are getting errors such as:
1282 : kernel: st0: MTSETDRVBUFFER only allowed for root
1286 you are most likely running your Storage daemon as non-root, and
1287 Bacula is attempting to set the correct OS buffering to correspond
1288 to your Device resource. Most OSes allow only root to issue this
1289 ioctl command. In general, the message can be ignored providing
1290 you are sure that your OS parameters are properly configured as
1291 described earlier in this manual. If you are running your Storage daemon
1292 as root, you should not be getting these system log messages, and if
1293 you are, something is probably wrong.