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
356 \subsection{Linux SCSI Tricks}
357 \index[general]{Tricks!Linux SCSI}
358 \index[general]{Linux SCSI Tricks}
360 You can find out what SCSI devices you have by doing:
372 [0:0:0:0] disk ATA ST3160812AS 3.AD /dev/sda
373 [2:0:4:0] tape HP Ultrium 2-SCSI F6CH /dev/st0
374 [2:0:5:0] tape HP Ultrium 2-SCSI F6CH /dev/st1
375 [2:0:6:0] mediumx OVERLAND LXB 0107 -
376 [2:0:9:0] tape HP Ultrium 1-SCSI E50H /dev/st2
377 [2:0:10:0] mediumx OVERLAND LXB 0107 -
381 There are two drives in one autochanger: /dev/st0 and /dev/st1
382 and a third tape drive at /dev/st2. For using them with Bacula, one
383 would normally reference them as /dev/nst0 ... /dev/nst2. Not also,
384 there are two different autochangers identified as "mediumx OVERLAND LXB".
385 They can be addressed via their /dev/sgN designation, which can be
386 obtained by counting from the beginning as 0 to each changer. In the
387 above case, the two changers are located on /dev/sg3 and /dev/sg5. The one
388 at /dev/sg3, controls drives /dev/nst0 and /dev/nst1; and the one at
389 /dev/sg5 controles drive /dev/nst2.
391 If you do not have the {\bf lsscsi} command, you can obtain the same
392 information as follows:
400 For the above example with the three drives and two autochangers,
406 Host: scsi0 Channel: 00 Id: 00 Lun: 00
407 Vendor: ATA Model: ST3160812AS Rev: 3.AD
408 Type: Direct-Access ANSI SCSI revision: 05
409 Host: scsi2 Channel: 00 Id: 04 Lun: 00
410 Vendor: HP Model: Ultrium 2-SCSI Rev: F6CH
411 Type: Sequential-Access ANSI SCSI revision: 03
412 Host: scsi2 Channel: 00 Id: 05 Lun: 00
413 Vendor: HP Model: Ultrium 2-SCSI Rev: F6CH
414 Type: Sequential-Access ANSI SCSI revision: 03
415 Host: scsi2 Channel: 00 Id: 06 Lun: 00
416 Vendor: OVERLAND Model: LXB Rev: 0107
417 Type: Medium Changer ANSI SCSI revision: 02
418 Host: scsi2 Channel: 00 Id: 09 Lun: 00
419 Vendor: HP Model: Ultrium 1-SCSI Rev: E50H
420 Type: Sequential-Access ANSI SCSI revision: 03
421 Host: scsi2 Channel: 00 Id: 10 Lun: 00
422 Vendor: OVERLAND Model: LXB Rev: 0107
423 Type: Medium Changer ANSI SCSI revision: 02
428 As an additional example, I get the following (on a different machine from the
434 Host: scsi2 Channel: 00 Id: 01 Lun: 00
435 Vendor: HP Model: C5713A Rev: H107
436 Type: Sequential-Access ANSI SCSI revision: 02
437 Host: scsi2 Channel: 00 Id: 04 Lun: 00
438 Vendor: SONY Model: SDT-10000 Rev: 0110
439 Type: Sequential-Access ANSI SCSI revision: 02
443 The above represents first an autochanger and second a simple
444 tape drive. The HP changer (the first entry) uses the same SCSI channel
445 for data and for control, so in Bacula, you would use:
448 Archive Device = /dev/nst0
449 Changer Device = /dev/sg0
453 If you want to remove the SDT-10000 device, you can do so as root with:
457 echo "scsi remove-single-device 2 0 4 0">/proc/scsi/scsi
461 and you can put add it back with:
465 echo "scsi add-single-device 2 0 4 0">/proc/scsi/scsi
469 where the 2 0 4 0 are the Host, Channel, Id, and Lun as seen on the output
470 from {\bf cat /proc/scsi/scsi}. Note, the Channel must be specified as
473 Below is a slightly more complicated output, which is a single autochanger
474 with two drives, and which operates the changer on a different channel
475 from from the drives:
480 Host: scsi0 Channel: 00 Id: 00 Lun: 00
481 Vendor: ATA Model: WDC WD1600JD-75H Rev: 08.0
482 Type: Direct-Access ANSI SCSI revision: 05
483 Host: scsi2 Channel: 00 Id: 04 Lun: 00
484 Vendor: HP Model: Ultrium 2-SCSI Rev: F6CH
485 Type: Sequential-Access ANSI SCSI revision: 03
486 Host: scsi2 Channel: 00 Id: 05 Lun: 00
487 Vendor: HP Model: Ultrium 2-SCSI Rev: F6CH
488 Type: Sequential-Access ANSI SCSI revision: 03
489 Host: scsi2 Channel: 00 Id: 06 Lun: 00
490 Vendor: OVERLAND Model: LXB Rev: 0106
491 Type: Medium Changer ANSI SCSI revision: 02
495 The above tape drives are accessed on /dev/nst0 and /dev/nst1, while
496 the control channel for those two drives is /dev/sg3.
501 \section{Tips for Resolving Problems}
502 \index[general]{Problems!Tips for Resolving}
503 \index[general]{Tips for Resolving Problems}
505 \label{CannotRestore}
506 \subsection{Bacula Saves But Cannot Restore Files}
507 \index[general]{Files!Bacula Saves But Cannot Restore}
508 \index[general]{Bacula Saves But Cannot Restore Files}
510 If you are getting error messages such as:
514 Volume data error at 0:1! Wanted block-id: "BB02", got "". Buffer discarded
518 It is very likely that Bacula has tried to do block positioning and ended up
519 at an invalid block. This can happen if your tape drive is in fixed block mode
520 while Bacula's default is variable blocks. Note that in such cases, Bacula is
521 perfectly able to write to your Volumes (tapes), but cannot position to read
524 There are two possible solutions.
527 \item The first and best is to always ensure that your drive is in variable
528 block mode. Note, it can switch back to fixed block mode on a reboot or if
529 another program uses the drive. So on such systems you need to modify the
530 Bacula startup files to explicitly set:
534 mt -f /dev/nst0 defblksize 0
538 or whatever is appropriate on your system. Note, if you are running a Linux
539 system, and the above command does not work, it is most likely because you
540 have not loaded the appropriate {\bf mt} package, which is often called
541 {\bf mt\_st}, but may differ according to your distribution.
543 \item The second possibility, especially, if Bacula wrote while the drive was
544 in fixed block mode, is to turn off block positioning in Bacula. This is done
549 Block Positioning = no
553 to the Device resource. This is not the recommended procedure because it can
554 enormously slow down recovery of files, but it may help where all else
555 fails. This directive is available in version 1.35.5 or later (and not yet
559 If you are getting error messages such as:
562 Volume data error at 0:0!
563 Block checksum mismatch in block=0 len=32625 calc=345678 blk=123456
567 You are getting tape read errors, and this is most likely due to
568 one of the following things:
570 \item An old or bad tape.
571 \item A dirty drive that needs cleaning (particularly for DDS drives).
572 \item A loose SCSI cable.
573 \item Old firmware in your drive. Make sure you have the latest firmware
575 \item Computer memory errors.
576 \item Over-clocking your CPU.
577 \item A bad SCSI card.
582 \subsection{Bacula Cannot Open the Device}
583 \index[general]{Device!Bacula Cannot Open the}
584 \index[general]{Bacula Cannot Open the Device}
586 If you get an error message such as:
590 dev open failed: dev.c:265 stored: unable to open
591 device /dev/nst0:> ERR=No such device or address
595 the first time you run a job, it is most likely due to the fact that you
596 specified the incorrect device name on your {\bf Archive Device}.
598 If Bacula works fine with your drive, then all off a sudden you get error
599 messages similar to the one shown above, it is quite possible that your driver
600 module is being removed because the kernel deems it idle. This is done via
601 {\bf crontab} with the use of {\bf rmmod -a}. To fix the problem, you can
602 remove this entry from {\bf crontab}, or you can manually {\bf modprob} your
603 driver module (or add it to the local startup script). Thanks to Alan Brown
605 \label{IncorrectFiles}
607 \subsection{Incorrect File Number}
608 \index[general]{Number!Incorrect File}
609 \index[general]{Incorrect File Number}
611 When Bacula moves to the end of the medium, it normally uses the {\bf
612 ioctl(MTEOM)} function. Then Bacula uses the {\bf ioctl(MTIOCGET)} function to
613 retrieve the current file position from the {\bf mt\_fileno} field. Some SCSI
614 tape drivers will use a fast means of seeking to the end of the medium and in
615 doing so, they will not know the current file position and hence return a {\bf
616 -1}. As a consequence, if you get {\bf "This is NOT correct!"} in the
617 positioning tests, this may be the cause. You must correct this condition in
618 order for Bacula to work.
620 There are two possible solutions to the above problem of incorrect file
624 \item Figure out how to configure your SCSI driver to keep track of the file
625 position during the MTEOM request. This is the preferred solution.
626 \item Modify the {\bf Device} resource of your {\bf bacula-sd.conf} file to
631 Hardware End of File = no
635 This will cause Bacula to use the MTFSF request to seek to the end of the
636 medium, and Bacula will keep track of the file number itself.
639 \label{IncorrectBlocks}
640 \subsection{Incorrect Number of Blocks or Positioning Errors}
641 \index[general]{Testing!Incorrect Number of Blocks or Positioning Errors}
642 \index[general]{Incorrect Number of Blocks or Positioning Errors}
644 {\bf Bacula's} preferred method of working with tape drives (sequential
645 devices) is to run in variable block mode, and this is what is set by default.
646 You should first ensure that your tape drive is set for variable block mode
649 If your tape drive is in fixed block mode and you have told Bacula to use
650 different fixed block sizes or variable block sizes (default), you will get
651 errors when Bacula attempts to forward space to the correct block (the kernel
652 driver's idea of tape blocks will not correspond to Bacula's).
654 All modern tape drives support variable tape blocks, but some older drives (in
655 particular the QIC drives) as well as the ATAPI ide-scsi driver run only in
656 fixed block mode. The Travan tape drives also apparently must run in fixed
657 block mode (to be confirmed).
659 Even in variable block mode, with the exception of the first record on the
660 second or subsequent volume of a multi-volume backup, Bacula will write blocks
661 of a fixed size. However, in reading a tape, Bacula will assume that for each
662 read request, exactly one block from the tape will be transferred. This the
663 most common way that tape drives work and is well supported by {\bf Bacula}.
665 Drives that run in fixed block mode can cause serious problems for Bacula if
666 the drive's block size does not correspond exactly to {\bf Bacula's} block
667 size. In fixed block size mode, drivers may transmit a partial block or
668 multiple blocks for a single read request. From {\bf Bacula's} point of view,
669 this destroys the concept of tape blocks. It is much better to run in variable
670 block mode, and almost all modern drives (the OnStream is an exception) run in
671 variable block mode. In order for Bacula to run in fixed block mode, you must
672 include the following records in the Storage daemon's Device resource
677 Minimum Block Size = nnn
678 Maximum Block Size = nnn
682 where {\bf nnn} must be the same for both records and must be identical to the
683 driver's fixed block size.
685 We recommend that you avoid this configuration if at all possible by using
686 variable block sizes.
688 If you must run with fixed size blocks, make sure they are not 512 bytes. This
689 is too small and the overhead that Bacula has with each record will become
690 excessive. If at all possible set any fixed block size to something like
691 64,512 bytes or possibly 32,768 if 64,512 is too large for your drive. See
692 below for the details on checking and setting the default drive block size.
694 To recover files from tapes written in fixed block mode, see below.
697 \subsection{Ensuring that the Tape Modes Are Properly Set -- {\bf Linux
699 \index[general]{Ensuring that the Tape Modes Are Properly Set -- Linux Only}
701 If you have a modern SCSI tape drive and you are having problems with the {\bf
702 test} command as noted above, it may be that some program has set one or more
703 of your SCSI driver's options to non-default values. For example, if your
704 driver is set to work in SysV manner, Bacula will not work correctly because
705 it expects BSD behavior. To reset your tape drive to the default values, you
706 can try the following, but {\bf ONLY} if you have a SCSI tape drive on a {\bf
712 mt -f /dev/nst0 rewind
713 mt -f /dev/nst0 stoptions buffer-writes async-writes read-ahead
717 The above commands will clear all options and then set those specified. None
718 of the specified options are required by Bacula, but a number of other options
719 such as SysV behavior must not be set. Bacula does not support SysV tape
720 behavior. On systems other than Linux, you will need to consult your {\bf mt}
721 man pages or documentation to figure out how to do the same thing. This should
722 not really be necessary though -- for example, on both Linux and Solaris
723 systems, the default tape driver options are compatible with Bacula.
724 On Solaris systems, you must take care to specify the correct device
725 name on the {\bf Archive device} directive. See above for more details.
727 You may also want to ensure that no prior program has set the default block
728 size, as happened to one user, by explicitly turning it off with:
732 mt -f /dev/nst0 defblksize 0
736 If you are running a Linux
737 system, and the above command does not work, it is most likely because you
738 have not loaded the appropriate {\bf mt} package, which is often called
739 {\bf mt\_st}, but may differ according to your distribution.
741 If you would like to know what options you have set before making any of the
742 changes noted above, you can now view them on Linux systems, thanks to a tip
743 provided by Willem Riede. Do the following:
748 mt -f /dev/nst0 stsetoptions 0
749 grep st0 /var/log/messages
753 and you will get output that looks something like the following:
757 kernel: st0: Mode 0 options: buffer writes: 1, async writes: 1, read ahead: 1
758 kernel: st0: can bsr: 0, two FMs: 0, fast mteom: 0, auto lock: 0,
759 kernel: st0: defs for wr: 0, no block limits: 0, partitions: 0, s2 log: 0
760 kernel: st0: sysv: 0 nowait: 0
764 Note, I have chopped off the beginning of the line with the date and machine
765 name for presentation purposes.
767 Some people find that the above settings only last until the next reboot, so
768 please check this otherwise you may have unexpected problems.
770 Beginning with Bacula version 1.35.8, if Bacula detects that you are running
771 in variable block mode, it will attempt to set your drive appropriately. All
772 OSes permit setting variable block mode, but some OSes do not permit setting
773 the other modes that Bacula needs to function properly.
776 \subsection{Tape Hardware Compression and Blocking Size}
777 \index[general]{Tape Hardware Compression and Blocking Size}
778 \index[general]{Size!Tape Hardware Compression and Blocking Size}
780 As far as I can tell, there is no way with the {\bf mt} program to check if
781 your tape hardware compression is turned on or off. You can, however, turn it
782 on by using (on Linux):
787 mt -f /dev/nst0 defcompression 1
791 and of course, if you use a zero instead of the one at the end, you will turn
794 If you have built the {\bf mtx} program in the {\bf depkgs} package, you can
795 use tapeinfo to get quite a bit of information about your tape drive even if
796 it is not an autochanger. This program is called using the SCSI control
797 device. On Linux for tape drive /dev/nst0, this is usually /dev/sg0, while on
798 FreeBSD for /dev/nsa0, the control device is often /dev/pass2. For example on
799 my DDS-4 drive (/dev/nst0), I get the following:
804 Product Type: Tape Drive
806 Product ID: 'C5713A '
815 Medium Type: Not Loaded
821 where the {\bf DataCompEnabled: yes} means that tape hardware compression is
822 turned on. You can turn it on and off (yes|no) by using the {\bf mt}
823 commands given above. Also, this output will tell you if the {\bf BlockSize}
824 is non-zero and hence set for a particular block size. Bacula is not likely to
825 work in such a situation because it will normally attempt to write blocks of
826 64,512 bytes, except the last block of the job which will generally be
827 shorter. The first thing to try is setting the default block size to zero
828 using the {\bf mt -f /dev/nst0 defblksize 0} command as shown above.
829 On FreeBSD, this would be something like: {\bf mt -f /dev/nsa0 blocksize 0}.
831 On some operating systems with some tape drives, the amount of data that
832 can be written to the tape and whether or not compression is enabled is
833 determined by the density usually the {\bf mt -f /dev/nst0 setdensity xxx} command.
834 Often {\bf mt -f /dev/nst0 status} will print out the current
835 density code that is used with the drive. Most systems, but unfortunately
836 not all, set the density to the maximum by default. On some systems, you
837 can also get a list of all available density codes with:
838 {\bf mt -f /dev/nst0 densities} or a similar {\bf mt} command.
839 Note, for DLT and SDLT devices, no-compression versus compression is very
840 often controlled by the density code. On FreeBSD systems, the compression
841 mode is set using {\bf mt -f /dev/nsa0 comp xxx} where xxx is the
842 mode you want. In general, see {\bf man mt} for the options available on
845 Note, some of the above {\bf mt} commands may not be persistent depending
846 on your system configuration. That is they may be reset if a program
847 other than Bacula uses the drive or, as is frequently the case, on reboot
850 If your tape drive requires fixed block sizes (very unusual), you can use the
855 Minimum Block Size = nnn
856 Maximum Block Size = nnn
860 in your Storage daemon's Device resource to force Bacula to write fixed size
861 blocks (where you sent nnn to be the same for both of the above records). This
862 should be done only if your drive does not support variable block sizes, or
863 you have some other strong reasons for using fixed block sizes. As mentioned
864 above, a small fixed block size of 512 or 1024 bytes will be very inefficient.
865 Try to set any fixed block size to something like 64,512 bytes or larger if
866 your drive will support it.
868 Also, note that the {\bf Medium Type} field of the output of {\bf tapeinfo}
869 reports {\bf Not Loaded}, which is not correct. As a consequence, you should
870 ignore that field as well as the {\bf Attached Changer} field.
872 To recover files from tapes written in fixed block mode, see below.
875 \subsection{Tape Modes on FreeBSD}
876 \index[general]{FreeBSD!Tape Modes on}
877 \index[general]{Tape Modes on FreeBSD}
879 On most FreeBSD systems such as 4.9 and most tape drives, Bacula should run
884 mt -f /dev/nsa0 seteotmodel 2
885 mt -f /dev/nsa0 blocksize 0
886 mt -f /dev/nsa0 comp enable
890 You might want to put those commands in a startup script to make sure your
891 tape driver is properly initialized before running Bacula, because
892 depending on your system configuration, these modes may be reset if a
893 program other than Bacula uses the drive or when your system is rebooted.
895 Then according to what the {\bf btape test} command returns, you will probably
896 need to set the following (see below for an alternative):
900 Hardware End of Medium = no
902 Backward Space Record = no
903 Backward Space File = no
904 Fast Forward Space File = no
909 Then be sure to run some append tests with Bacula where you start and stop
910 Bacula between appending to the tape, or use {\bf btape} version 1.35.1 or
911 greater, which includes simulation of stopping/restarting Bacula.
913 Please see the file {\bf platforms/freebsd/pthreads-fix.txt} in the main
914 Bacula directory concerning {\bf important} information concerning
915 compatibility of Bacula and your system. A much more optimal Device
916 configuration is shown below, but does not work with all tape drives. Please
917 test carefully before putting either into production.
919 Note, for FreeBSD 4.10-RELEASE, using a Sony TSL11000 L100 DDS4 with an
920 autochanger set to variable block size and DCLZ compression, Brian McDonald
921 reports that to get Bacula to append correctly between Bacula executions,
922 the correct values to use are:
926 mt -f /dev/nsa0 seteotmodel 1
927 mt -f /dev/nsa0 blocksize 0
928 mt -f /dev/nsa0 comp enable
936 Hardware End of Medium = no
938 Backward Space Record = no
939 Backward Space File = no
940 Fast Forward Space File = yes
945 This has been confirmed by several other people using different hardware. This
946 configuration is the preferred one because it uses one EOF and no backspacing
947 at the end of the tape, which works much more efficiently and reliably with
950 Finally, here is a Device configuration that Danny Butroyd reports to work
951 correctly with the Overland Powerloader tape library using LT0-2 and
956 # Overland Powerloader LT02 - 17 slots single drive
960 Archive Device = /dev/nsa0
961 AutomaticMount = yes;
963 RemovableMedia = yes;
965 Changer Command = "/usr/local/sbin/mtx-changer %c %o %S %a %d"
966 Changer Device = /dev/pass2
968 Alert Command = "sh -c 'tapeinfo -f %c |grep TapeAlert|cat'"
970 # FreeBSD Specific Settings
971 Offline On Unmount = no
972 Hardware End of Medium = no
974 Backward Space Record = no
975 Fast Forward Space File = no
979 The following Device resource works fine with Dell PowerVault 110T and
980 120T devices on both FreeBSD 5.3 and on NetBSD 3.0. It also works
981 with Sony AIT-2 drives on FreeBSD.
986 # FreeBSD/NetBSD Specific Settings
987 Hardware End of Medium = no
989 Backward Space Record = no
990 Fast Forward Space File = yes
996 On FreeBSD version 6.0, it is reported that you can even set
997 Backward Space Record = yes.
1001 \subsection{Finding your Tape Drives and Autochangers on FreeBSD}
1002 \index[general]{FreeBSD!Finding Tape Drives and Autochangers}
1003 \index[general]{Finding Tape Drives and Autochangers on FreeBSD}
1005 On FreeBSD, you can do a {\bf camcontrol devlist} as root to determine what
1006 drives and autochangers you have. For example,
1010 undef# camcontrol devlist
1011 at scbus0 target 2 lun 0 (pass0,sa0)
1012 at scbus0 target 4 lun 0 (pass1,sa1)
1013 at scbus0 target 4 lun 1 (pass2)
1017 from the above, you can determine that there is a tape drive on {\bf /dev/sa0}
1018 and another on {\bf /dev/sa1} in addition since there is a second line for the
1019 drive on {\bf /dev/sa1}, you know can assume that it is the control device for
1020 the autochanger (i.e. {\bf /dev/pass2}). It is also the control device name to
1021 use when invoking the tapeinfo program. E.g.
1025 tapeinfo -f /dev/pass2
1031 \subsection{Using the OnStream driver on Linux Systems}
1032 \index[general]{Using the OnStream driver on Linux Systems}
1033 \index[general]{Systems!Using the OnStream driver on Linux}
1035 Bacula version 1.33 (not 1.32x) is now working and ready for testing with the
1036 OnStream kernel osst driver version 0.9.14 or above. Osst is available from:
1037 \elink{http://sourceforge.net/projects/osst/}
1038 {http://sourceforge.net/projects/osst/}.
1040 To make Bacula work you must first load the new driver then, as root, do:
1044 mt -f /dev/nosst0 defblksize 32768
1048 Also you must add the following to your Device resource in your Storage
1053 Minimum Block Size = 32768
1054 Maximum Block Size = 32768
1058 Here is a Device specification provided by Michel Meyers that is known to
1064 Name = "Onstream DI-30"
1065 Media Type = "ADR-30"
1066 Archive Device = /dev/nosst0
1067 Minimum Block Size = 32768
1068 Maximum Block Size = 32768
1069 Hardware End of Medium = yes
1071 Backward Space File = yes
1072 Fast Forward Space File = yes
1074 AutomaticMount = yes
1076 Removable Media = yes
1081 \section{Hardware Compression on EXB-8900}
1082 \index[general]{Hardware Compression on EXB-8900}
1083 \index[general]{EXB-8900!Hardware Compression}
1085 To active, check, or disable the hardware compression feature
1086 on an EXB-8900, use the exabyte MammothTool. You can get it here:
1087 \elink{http://www.exabyte.com/support/online/downloads/index.cfm}
1088 {http://www.exabyte.com/support/online/downloads/index.cfm}.
1089 There is a Solaris version of this tool. With option -C 0 or 1 you
1090 can disable or activate compression. Start this tool without any
1091 options for a small reference.
1094 \subsection{Using btape to Simulate Filling a Tape}
1095 \index[general]{Using btape to Simulate Filling a Tape}
1096 \index[general]{Tape!Using btape to Simulate Filling}
1098 Because there are often problems with certain tape drives or systems when end
1099 of tape conditions occur, {\bf btape} has a special command {\bf fill} that
1100 causes it to write random data to a tape until the tape fills. It then writes
1101 at least one more Bacula block to a second tape. Finally, it reads back both
1102 tapes to ensure that the data has been written in a way that Bacula can
1103 recover it. Note, there is also a single tape option as noted below, which you
1104 should use rather than the two tape test. See below for more details.
1106 This can be an extremely time consuming process (here it is about 6 hours) to
1107 fill a full tape. Note, that btape writes random data to the tape when it is
1108 filling it. This has two consequences: 1. it takes a bit longer to generate
1109 the data, especially on slow CPUs. 2. the total amount of data is
1110 approximately the real physical capacity of your tape, regardless of whether
1111 or not the tape drive compression is on or off. This is because random data
1112 does not compress very much.
1114 To begin this test, you enter the {\bf fill} command and follow the
1115 instructions. There are two options: the simple single tape option and the
1116 multiple tape option. Please use only the simple single tape option because
1117 the multiple tape option still doesn't work totally correctly. If the single
1118 tape option does not succeed, you should correct the problem before using
1120 \label{RecoveringFiles}
1122 \section{Recovering Files Written With Fixed Block Sizes}
1123 \index[general]{Recovering Files Written With Fixed Block Sizes}
1125 If you have been previously running your tape drive in fixed block mode
1126 (default 512) and Bacula with variable blocks (default), then in version
1127 1.32f-x and 1.34 and above, Bacula will fail to recover files because it does
1128 block spacing, and because the block sizes don't agree between your tape drive
1129 and Bacula it will not work.
1131 The long term solution is to run your drive in variable block mode as
1132 described above. However, if you have written tapes using fixed block sizes,
1133 this can be a bit of a pain. The solution to the problem is: while you are
1134 doing a restore command using a tape written in fixed block size, ensure that
1135 your drive is set to the fixed block size used while the tape was written.
1136 Then when doing the {\bf restore} command in the Console program, do not
1137 answer the prompt {\bf yes/mod/no}. Instead, edit the bootstrap file (the
1138 location is listed in the prompt) using any ASCII editor. Remove all {\bf
1139 VolBlock} lines in the file. When the file is re-written, answer the question,
1140 and Bacula will run without using block positioning, and it should recover
1144 \section{Tape Blocking Modes}
1145 \index[general]{Modes!Tape Blocking}
1146 \index[general]{Tape Blocking Modes}
1148 SCSI tapes may either be written in {\bf variable} or {\bf fixed} block sizes.
1149 Newer drives support both modes, but some drives such as the QIC devices
1150 always use fixed block sizes. Bacula attempts to fill and write complete
1151 blocks (default 65K), so that in normal mode (variable block size), Bacula
1152 will always write blocks of the same size except the last block of a Job. If
1153 Bacula is configured to write fixed block sizes, it will pad the last block of
1154 the Job to the correct size. Bacula expects variable tape block size drives to
1155 behave as follows: Each write to the drive results in a single record being
1156 written to the tape. Each read returns a single record. If you request less
1157 bytes than are in the record, only those number of bytes will be returned, but
1158 the entire logical record will have been read (the next read will retrieve the
1159 next record). Thus data from a single write is always returned in a single
1160 read, and sequentially written records are returned by sequential reads.
1162 Bacula expects fixed block size tape drives to behave as follows: If a write
1163 length is greater than the physical block size of the drive, the write will be
1164 written as two blocks each of the fixed physical size. This single write may
1165 become multiple physical records on the tape. (This is not a good situation).
1166 According to the documentation, one may never write an amount of data that is
1167 not the exact multiple of the blocksize (it is not specified if an error
1168 occurs or if the the last record is padded). When reading, it is my
1169 understanding that each read request reads one physical record from the tape.
1170 Due to the complications of fixed block size tape drives, you should avoid
1171 them if possible with Bacula, or you must be ABSOLUTELY certain that you use
1172 fixed block sizes within Bacula that correspond to the physical block size of
1173 the tape drive. This will ensure that Bacula has a one to one correspondence
1174 between what it writes and the physical record on the tape.
1176 Please note that Bacula will not function correctly if it writes a block and
1177 that block is split into two or more physical records on the tape. Bacula
1178 assumes that each write causes a single record to be written, and that it can
1179 sequentially recover each of the blocks it has written by using the same
1180 number of sequential reads as it had written.
1182 \section{Details of Tape Modes}
1183 \index[general]{Modes!Details}
1184 \index[general]{Details of Tape Modes}
1185 Rudolf Cejka has provided the following information concerning
1186 certain tape modes and MTEOM.
1190 It is always possible to position filemarks or blocks, whereas
1191 positioning to the end-of-data is only optional feature, however it is
1192 implemented very often. SCSI specification also talks about optional
1193 sequential filemarks, setmarks and sequential setmarks, but these are not
1194 implemented so often. Modern tape drives keep track of file positions in
1195 built-in chip (AIT, LTO) or at the beginning of the tape (SDLT), so there
1196 is not any speed difference, if end-of-data or filemarks is used (I have
1197 heard, that LTO-1 from all 3 manufacturers do not use its chip for file
1198 locations, but a tape as in SDLT case, and I'm not sure about LTO-2 and
1199 LTO-3 case). However there is a big difference, that end-of-data ignores
1200 file position, whereas filemarks returns the real number of skipped
1201 files, so OS can track current file number just in filemarks case.
1204 Solaris does use just SCSI SPACE Filemarks, it does not support SCSI
1205 SPACE End-of-data. When MTEOM is called, Solaris does use SCSI SPACE
1206 Filemarks with count = 1048576 for fast mode, and combination of SCSI
1207 SPACE Filemarks with count = 1 with SCSI SPACE Blocks with count = 1 for
1208 slow mode, so EOD mark on the tape on some older tape drives is not
1209 skipped. File number is always tracked for MTEOM.
1211 Linux does support both SCSI SPACE Filemarks and End-of-data: When MTEOM
1212 is called in MT\_ST\_FAST\_MTEOM mode, SCSI SPACE End-of-data is used.
1213 In the other case, SCSI SPACE Filemarks with count =
1215 There is no real slow mode like in Solaris - I just expect, that for
1216 older tape drives Filemarks may be slower than End-of-data, but not so
1217 much as in Solaris slow mode. File number is tracked for MTEOM just
1218 without MT\_ST\_FAST\_MTEOM - when MT\_ST\_FAST\_MTEOM is used, it is not.
1220 FreeBSD does support both SCSI SPACE Filemarks and End-of-data, but when
1221 MTEOD (MTEOM) is called, SCSI SPACE End-of-data is always used. FreeBSD
1222 never use SCSI SPACE Filemarks for MTEOD. File number is never tracked
1226 When {\bf Hardware End of Medium = Yes} is used, MTEOM is called, but it
1227 does not mean, that hardware End-of-data must be used. When Hardware End
1228 of Medium = No, if Fast Forward Space File = Yes, MTFSF with count =
1229 32767 is used, else Block Read with count = 1 with Forward Space File
1230 with count = 1 is used, which is really very slow.
1232 \item [Hardware End of Medium = Yes|No]
1233 The name of this option is misleading and is the source of confusion,
1234 because it is not the hardware EOM, what is really switched here.
1236 If I use Yes, OS must not use SCSI SPACE End-of-data, because Bacula
1237 expects, that there is tracked file number, which is not supported by
1238 SCSI specification. Instead, the OS have to use SCSI SPACE Filemarks.
1240 If I use No, an action depends on Fast Forward Space File.
1242 When I set {\bf Hardware End of Medium = no}
1243 and {\bf Fast Forward Space File = no}
1244 file positioning was very slow
1245 on my LTO-3 (about ten to 100 minutes), but
1247 with {\bf Hardware End of Medium = no} and
1248 {\bf Fast Forward Space File = yes}, the time is ten to
1249 100 times faster (about one to two minutes).
1253 \section{Autochanger Errors}
1254 \index[general]{Errors!Autochanger}
1255 \index[general]{Autochanger Errors}
1257 If you are getting errors such as:
1261 3992 Bad autochanger "load slot 1, drive 1": ERR=Child exited with code 1.
1265 and you are running your Storage daemon as non-root, then most likely
1266 you are having permissions problems with the control channel. Running
1267 as root, set permissions on /dev/sgX so that the userid and group of
1268 your Storage daemon can access the device. You need to ensure that you
1269 all access to the proper control device, and if you don't have any
1270 SCSI disk drives (including SATA drives), you might want to change
1271 the permissions on /dev/sg*.
1273 \section{Syslog Errors}
1274 \index[general]{Errors!Syslog}
1275 \index[general]{Syslog Errors}
1277 If you are getting errors such as:
1281 : kernel: st0: MTSETDRVBUFFER only allowed for root
1285 you are most likely running your Storage daemon as non-root, and
1286 Bacula is attempting to set the correct OS buffering to correspond
1287 to your Device resource. Most OSes allow only root to issue this
1288 ioctl command. In general, the message can be ignored providing
1289 you are sure that your OS parameters are properly configured as
1290 described earlier in this manual. If you are running your Storage daemon
1291 as root, you should not be getting these system log messages, and if
1292 you are, something is probably wrong.