4 \section*{Testing Your Tape Drive With Bacula}
5 \label{_ChapterStart27}
6 \index[general]{Testing Your Tape Drive With Bacula}
7 \addcontentsline{toc}{section}{Testing Your Tape Drive With Bacula}
9 This chapter is concerned with testing and configuring your tape drive to make
10 sure that it will work properly with Bacula using the {\bf btape} program.
13 \subsection*{Summary of Steps to Take to Get Your Tape Drive Working}
14 \index[general]{Working!Summary of Steps to Take to Get Your Tape Drive}
15 \index[general]{Summary of Steps to Take to Get Your Tape Drive Working}
16 \addcontentsline{toc}{subsection}{Summary of Steps to Take to Get Your Tape
19 In general, you should follow the following steps to get your tape drive to
20 work with Bacula. Start with a tape mounted in your drive. If you have an
21 autochanger, load a tape into the drive. We use {\bf /dev/nst0} as the tape
22 drive name, you will need to adapt it according to your system.
24 Do not proceed to the next item until you have succeeded with the previous
28 \item Use tar to write to, then read from your drive:
32 mt -f /dev/nst0 rewind
34 mt -f /dev/nst0 rewind
40 \item Make sure you have a valid and correct Device resource corresponding to
41 your drive. For Linux users, generally, the default one works. For FreeBSD
42 users, there are two possible Device configurations (see below).
43 \item Run the btape {\bf test} command:
47 ./btape -c bacula-sd.conf /dev/nst0
53 It isn't necessary to run the autochanger part of the test at this time, but
54 do not go past this point until the basic test succeeds. If you do have
55 an autochanger, please be sure to read the
56 \ilink{Autochanger chapter}{_ChapterStart18} of this manual.
58 \item Run the btape {\bf fill} command, preferably with two volumes. This
59 can take a long time. If you have an autochanger and it is configured, Bacula
60 will automatically use it. If you do not have it configured, you can manually
61 issue the appopriate {\bf mtx} command, or press the autochanger buttons to
62 change the tape when requested to do so.
63 \item FreeBSD users, if you have a pre-5.0 system run the {\bf tapetest}
64 program, and make sure your system is patched if necessary. The tapetest
65 program can be found in the platform/freebsd directory. The instructions
66 for its use are at the top of the file.
67 \item Run Bacula, and backup a reasonably small directory, say 60 Megabytes.
68 Do three successive backups of this directory.
69 \item Stop Bacula, then restart it. Do another full backup of the same
70 directory. Then stop and restart Bacula.
71 \item Do a restore of the directory backed up, by entering the following
72 restore command, being careful to restore it to an alternate location:
76 restore select all done
82 Do a {\bf diff} on the restored directory to ensure it is identical to the
84 \item If you have an autochanger, you should now go back to the btape program
85 and run the autochanger test:
89 ./btape -c bacula-sd.conf /dev/nst0
95 Adjust your autochanger as necessary to ensure that it works correctly. See
96 the Autochanger chapter of this manual for a complete discussion of testing
100 If you have reached this point, you stand a good chance of having everything
101 work. If you get into trouble at any point, {\bf carefully} read the
102 documentation given below. If you cannot get past some point, ask the {\bf
103 bacula-users} email list, but specify which of the steps you have successfully
104 completed. In particular, you may want to look at the
105 \ilink{ Tips for Resolving Problems}{problems1} section below.
107 \label{NoTapeInDrive}
108 \subsubsection*{Problems When no Tape in Drive}
109 \index[general]{Problems When no Tape in Drive}
110 \addcontentsline{toc}{subsubsection}{Problems When no Tape in Drive}
111 When Bacula was first written the Linux 2.4 kernel permitted opening the
112 drive whether or not there was a tape in the drive. Thus the Bacula code is
113 based on the concept that if the drive cannot be opened, there is a serious
114 problem, and the job is failed.
116 With version 2.6 of the Linux kernel, if there is no tape in the drive, the
117 OS will wait 2 minutes (default) then return a failure, and consequently,
118 Bacula version 1.36 and below will fail the job. This is important to keep
119 in mind, because if you use and option such as {\bf Offline on Unmount =
120 yes}, there will be a point when there is no tape in the drive, and if
121 another job starts or if Bacula asks the operator to mount a tape, when
122 Bacula attempts to open the drive (about a 20 minute delay), it will fail
123 and Bacula will fail the job.
125 In version 1.38.x, the Bacula code partially gets around this problem -- at
126 least in the initial open of the drive. However, functions like Polling
127 the drive do not work correctly if there is no tape in the drive.
128 Providing you do not use {\bf Offline on Unmount = yes}, you should not
129 experience job failures as mentioned above. If you do experience such
130 failures, you can also increase the {\bf Maximum Open Wait} time interval,
131 which will give you more time to mount the next tape before the job is
134 \subsubsection*{Specifying the Configuration File}
135 \index[general]{File!Specifying the Configuration}
136 \index[general]{Specifying the Configuration File}
137 \addcontentsline{toc}{subsubsection}{Specifying the Configuration File}
139 Starting with version 1.27, each of the tape utility programs including the
140 {\bf btape} program requires a valid Storage daemon configuration file
141 (actually, the only part of the configuration file that {\bf btape} needs is
142 the {\bf Device} resource definitions). This permits {\bf btape} to find the
143 configuration parameters for your archive device (generally a tape drive).
144 Without those parameters, the testing and utility programs do not know how to
145 properly read and write your drive. By default, they use {\bf bacula-sd.conf}
146 in the current directory, but you may specify a different configuration file
147 using the {\bf -c} option.
149 \subsubsection*{Specifying a Device Name For a Tape}
150 \index[general]{Tape!Specifying a Device Name For a}
151 \index[general]{Specifying a Device Name For a Tape}
152 \addcontentsline{toc}{subsubsection}{Specifying a Device Name For a Tape}
154 {\bf btape} {\bf device-name} where the Volume can be found. In the case of a
155 tape, this is the physical device name such as {\bf /dev/nst0} or {\bf
156 /dev/rmt/0ubn} depending on your system that you specify on the Archive Device
157 directive. For the program to work, it must find the identical name in the
158 Device resource of the configuration file. If the name is not found in the
159 list of phsical names, the utility program will compare the name you entered
160 to the Device names (rather than the Archive device names).
162 When specifying a tape device, it is preferable that the "non-rewind"
163 variant of the device file name be given. In addition, on systems such as
164 Sun, which have multiple tape access methods, you must be sure to specify
165 to use Berkeley I/O conventions with the device. The
166 {\bf b} in the Solaris (Sun) archive specification {\bf /dev/rmt/0mbn} is
167 what is needed in this case. Bacula does not support SysV tape drive
170 See below for specifying Volume names.
172 \subsubsection*{Specifying a Device Name For a File}
173 \index[general]{File!Specifying a Device Name For a}
174 \index[general]{Specifying a Device Name For a File}
175 \addcontentsline{toc}{subsubsection}{Specifying a Device Name For a File}
177 If you are attempting to read or write an archive file rather than a tape, the
178 {\bf device-name} should be the full path to the archive location including
179 the filename. The filename (last part of the specification) will be stripped
180 and used as the Volume name, and the path (first part before the filename)
181 must have the same entry in the configuration file. So, the path is equivalent
182 to the archive device name, and the filename is equivalent to the volume name.
187 \index[general]{Btape}
188 \addcontentsline{toc}{subsection}{btape}
190 This program permits a number of elementary tape operations via a tty command
191 interface. The {\bf test} command, described below, can be very useful for
192 testing tape drive compatibility problems. Aside from initial testing of tape
193 drive compatibility with {\bf Bacula}, {\bf btape} will be mostly used by
194 developers writing new tape drivers.
196 {\bf btape} can be dangerous to use with existing {\bf Bacula} tapes because
197 it will relabel a tape or write on the tape if so requested regardless of
198 whether or not the tape contains valuable data, so please be careful and use
199 it only on blank tapes.
201 To work properly, {\bf btape} needs to read the Storage daemon's configuration
202 file. As a default, it will look for {\bf bacula-sd.conf} in the current
203 directory. If your configuration file is elsewhere, please use the {\bf -c}
204 option to specify where.
206 The physical device name or the Device resource name must be specified on the
207 command line, and this same device name must be present in the Storage
208 daemon's configuration file read by {\bf btape}
212 Usage: btape [options] device_name
213 -b <file> specify bootstrap file
214 -c <file> set configuration file to file
215 -d <nn> set debug level to nn
216 -p proceed inspite of I/O errors
219 -? print this message.
223 \subsubsection*{Using btape to Verify your Tape Drive}
224 \index[general]{Using btape to Verify your Tape Drive}
225 \index[general]{Drive!Using btape to Verify your Tape}
226 \addcontentsline{toc}{subsubsection}{Using btape to Verify your Tape Drive}
228 An important reason for this program is to ensure that a Storage daemon
229 configuration file is defined so that Bacula will correctly read and write
232 It is highly recommended that you run the {\bf test} command before running
233 your first Bacula job to ensure that the parameters you have defined for your
234 storage device (tape drive) will permit {\bf Bacula} to function properly. You
235 only need to mount a blank tape, enter the command, and the output should be
236 reasonably self explanatory. For example:
240 (ensure that Bacula is not running)
241 ./btape -c /usr/bin/bacula/bacula-sd.conf /dev/nst0
249 Tape block granularity is 1024 bytes.
250 btape: btape.c:376 Using device: /dev/nst0
255 Enter the test command:
263 The output produced should be something similar to the following: I've cut the
264 listing short because it is frequently updated to have new tests.
268 === Append files test ===
269 This test is essential to Bacula.
270 I'm going to write one record in file 0,
271 two records in file 1,
272 and three records in file 2
273 btape: btape.c:387 Rewound /dev/nst0
274 btape: btape.c:855 Wrote one record of 64412 bytes.
275 btape: btape.c:857 Wrote block to device.
276 btape: btape.c:410 Wrote EOF to /dev/nst0
277 btape: btape.c:855 Wrote one record of 64412 bytes.
278 btape: btape.c:857 Wrote block to device.
279 btape: btape.c:855 Wrote one record of 64412 bytes.
280 btape: btape.c:857 Wrote block to device.
281 btape: btape.c:410 Wrote EOF to /dev/nst0
282 btape: btape.c:855 Wrote one record of 64412 bytes.
283 btape: btape.c:857 Wrote block to device.
284 btape: btape.c:855 Wrote one record of 64412 bytes.
285 btape: btape.c:857 Wrote block to device.
286 btape: btape.c:855 Wrote one record of 64412 bytes.
287 btape: btape.c:857 Wrote block to device.
288 btape: btape.c:410 Wrote EOF to /dev/nst0
289 btape: btape.c:387 Rewound /dev/nst0
290 btape: btape.c:693 Now moving to end of media.
291 btape: btape.c:427 Moved to end of media
292 We should be in file 3. I am at file 3. This is correct!
293 Now the important part, I am going to attempt to append to the tape.
295 === End Append files test ===
299 If you do not successfully complete the above test, please resolve the
300 problem(s) before attempting to use {\bf Bacula}. Depending on your tape
301 drive, the test may recommend that you add certain records to your
302 configuration. We strongly recommend that you do so and then re-run the above
303 test to insure it works the first time.
305 Some of the suggestions it provides for resolving the problems may or may not
306 be useful. If at all possible avoid using fixed blocking. If the test suddenly
307 starts to print a long series of:
317 then almost certainly, you are running your drive in fixed block mode rather
318 than variable block mode. See below for more help of resolving fix
319 versus variable block problems.
321 It is also possible that you have your drive
322 set in SysV tape drive mode. The drive must use BSD tape conventions.
323 See the section above on setting your {\bf Archive device} correctly.
325 For FreeBSD users, please see the notes below for doing further testing of
328 \subsubsection*{Linux SCSI Tricks}
329 \index[general]{Tricks!Linux SCSI}
330 \index[general]{Linux SCSI Tricks}
331 \addcontentsline{toc}{subsubsection}{Linux SCSI Tricks}
333 You can find out what SCSI devices you have by doing:
341 For example, I get the following:
346 Host: scsi2 Channel: 00 Id: 01 Lun: 00
347 Vendor: HP Model: C5713A Rev: H107
348 Type: Sequential-Access ANSI SCSI revision: 02
349 Host: scsi2 Channel: 00 Id: 04 Lun: 00
350 Vendor: SONY Model: SDT-10000 Rev: 0110
351 Type: Sequential-Access ANSI SCSI revision: 02
355 The above represents first an autochanger and second a simple
356 tape drive. The HP changer (the first entry) uses the same SCSI channel
357 for data and for control, so in Bacula, you would use:
360 Archive Device = /dev/nst0
361 Changer Device = /dev/sg0
365 If you want to remove the SDT-10000 device, you can do so as root with:
369 echo "scsi remove-single-device 2 0 4 0">/proc/scsi/scsi
373 and you can put add it back with:
377 echo "scsi add-single-device 2 0 4 0">/proc/scsi/scsi
381 where the 2 0 4 0 are the Host, Channel, Id, and Lun as seen on the output
382 from {\bf cat /proc/scsi/scsi}. Note, the Channel must be specified as
385 Below is a slightly more complicated output, which is a single autochanger
386 with two drives, and which operates the changer on a different channel
387 from from the drives:
392 Host: scsi0 Channel: 00 Id: 00 Lun: 00
393 Vendor: ATA Model: WDC WD1600JD-75H Rev: 08.0
394 Type: Direct-Access ANSI SCSI revision: 05
395 Host: scsi2 Channel: 00 Id: 04 Lun: 00
396 Vendor: HP Model: Ultrium 2-SCSI Rev: F6CH
397 Type: Sequential-Access ANSI SCSI revision: 03
398 Host: scsi2 Channel: 00 Id: 05 Lun: 00
399 Vendor: HP Model: Ultrium 2-SCSI Rev: F6CH
400 Type: Sequential-Access ANSI SCSI revision: 03
401 Host: scsi2 Channel: 00 Id: 06 Lun: 00
402 Vendor: OVERLAND Model: LXB Rev: 0106
403 Type: Medium Changer ANSI SCSI revision: 02
407 The above tape drives are accessed on /dev/nst0 and /dev/nst1, while
408 the control channel for those two drives is /dev/sg3.
413 \subsection*{Tips for Resolving Problems}
414 \index[general]{Problems!Tips for Resolving}
415 \index[general]{Tips for Resolving Problems}
416 \addcontentsline{toc}{subsection}{Tips for Resolving Problems}
418 \label{CannotRestore}
419 \subsubsection*{Bacula Saves But Cannot Restore Files}
420 \index[general]{Files!Bacula Saves But Cannot Restore}
421 \index[general]{Bacula Saves But Cannot Restore Files}
422 \addcontentsline{toc}{subsubsection}{Bacula Saves But Cannot Restore Files}
424 If you are getting error messages such as:
428 Volume data error at 0:1! Wanted block-id: "BB02", got "". Buffer discarded
432 It is very likely that Bacula has tried to do block positioning and ended up
433 at an invalid block. This can happen if your tape drive is in fixed block mode
434 while Bacula's default is variable blocks. Note that in such cases, Bacula is
435 perfectly able to write to your Volumes (tapes), but cannot position to read
438 There are two possible solutions.
441 \item The first and best is to always ensure that your drive is in variable
442 block mode. Note, it can switch back to fixed block mode on a reboot or if
443 another program uses the drive. So on such systems you need to modify the
444 Bacula startup files to explicitly set:
448 mt -f /dev/nst0 defblksize 0
452 or whatever is appropriate on your system.
453 \item The second possibility, especially, if Bacula wrote while the drive was
454 in fixed block mode, is to turn off block positioning in Bacula. This is done
459 Block Positioning = no
463 to the Device resource. This is not the recommended procedure because it can
464 enormously slow down recovery of files, but it may help where all else
465 fails. This directive is available in version 1.35.5 or later (and not yet
469 If you are getting error messages such as:
472 Volume data error at 0:0!
473 Block checksum mismatch in block=0 len=32625 calc=345678 blk=123456
477 You are getting tape read errors, and this is most likely due to
478 one of the following things:
480 \item An old or bad tape.
481 \item A dirty drive that needs cleaning (particularly for DDS drives).
482 \item A loose SCSI cable.
483 \item Old firmware in your drive. Make sure you have the latest firmware
485 \item Computer memory errors.
486 \item Over-clocking your CPU.
487 \item A bad SCSI card.
492 \subsubsection*{Bacula Cannot Open the Device}
493 \index[general]{Device!Bacula Cannot Open the}
494 \index[general]{Bacula Cannot Open the Device}
495 \addcontentsline{toc}{subsubsection}{Bacula Cannot Open the Device}
497 If you get an error message such as:
501 dev open failed: dev.c:265 stored: unable to open
502 device /dev/nst0:> ERR=No such device or address
506 the first time you run a job, it is most likely due to the fact that you
507 specified the incorrect device name on your {\bf Archive Device}.
509 If Bacula works fine with your drive, then all off a sudden you get error
510 messages similar to the one shown above, it is quite possible that your driver
511 module is being removed because the kernel deems it idle. This is done via
512 {\bf crontab} with the use of {\bf rmmod -a}. To fix the problem, you can
513 remove this entry from {\bf crontab}, or you can manually {\bf modprob} your
514 driver module (or add it to the local startup script). Thanks to Alan Brown
516 \label{IncorrectFiles}
518 \subsubsection*{Incorrect File Number}
519 \index[general]{Number!Incorrect File}
520 \index[general]{Incorrect File Number}
521 \addcontentsline{toc}{subsubsection}{Incorrect File Number}
523 When Bacula moves to the end of the medium, it normally uses the {\bf
524 ioctl(MTEOM)} function. Then Bacula uses the {\bf ioctl(MTIOCGET)} function to
525 retrieve the current file position from the {\bf mt\_fileno} field. Some SCSI
526 tape drivers will use a fast means of seeking to the end of the medium and in
527 doing so, they will not know the current file position and hence return a {\bf
528 -1}. As a consequence, if you get {\bf "This is NOT correct!"} in the
529 positioning tests, this may be the cause. You must correct this condition in
530 order for Bacula to work.
532 There are two possible solutions to the above problem of incorrect file
536 \item Figure out how to configure your SCSI driver to keep track of the file
537 position during the MTEOM request. This is the preferred solution.
538 \item Modify the {\bf Device} resource of your {\bf bacula-sd.conf} file to
543 Hardware End of File = no
547 This will cause Bacula to use the MTFSF request to seek to the end of the
548 medium, and Bacula will keep track of the file number itself.
551 \label{IncorrectBlocks}
552 \subsubsection*{Incorrect Number of Blocks or Positioning Errors during btape
554 \index[general]{Testing!Incorrect Number of Blocks or Positioning Errors
556 \index[general]{Incorrect Number of Blocks or Positioning Errors during btape
558 \addcontentsline{toc}{subsubsection}{Incorrect Number of Blocks or Positioning
559 Errors during btape Testing}
561 {\bf Bacula's} preferred method of working with tape drives (sequential
562 devices) is to run in variable block mode, and this is what is set by default.
563 You should first ensure that your tape drive is set for variable block mode
566 If your tape drive is in fixed block mode and you have told Bacula to use
567 different fixed block sizes or variable block sizes (default), you will get
568 errors when Bacula attempts to forward space to the correct block (the kernel
569 driver's idea of tape blocks will not correspond to Bacula's).
571 All modern tape drives support variable tape blocks, but some older drives (in
572 particular the QIC drives) as well as the ATAPI ide-scsi driver run only in
573 fixed block mode. The Travan tape drives also apparently must run in fixed
574 block mode (to be confirmed).
576 Even in variable block mode, with the exception of the first record on the
577 second or subsequent volume of a multi-volume backup, Bacula will write blocks
578 of a fixed size. However, in reading a tape, Bacula will assume that for each
579 read request, exactly one block from the tape will be transferred. This the
580 most common way that tape drives work and is well supported by {\bf Bacula}.
582 Drives that run in fixed block mode can cause serious problems for Bacula if
583 the drive's block size does not correspond exactly to {\bf Bacula's} block
584 size. In fixed block size mode, drivers may transmit a partial block or
585 multiple blocks for a single read request. From {\bf Bacula's} point of view,
586 this destroys the concept of tape blocks. It is much better to run in variable
587 block mode, and almost all modern drives (the OnStream is an exception) run in
588 variable block mode. In order for Bacula to run in fixed block mode, you must
589 include the following records in the Storage daemon's Device resource
594 Minimum Block Size = nnn
595 Maximum Block Size = nnn
599 where {\bf nnn} must be the same for both records and must be identical to the
600 driver's fixed block size.
602 We recommend that you avoid this configuration if at all possible by using
603 variable block sizes.
605 If you must run with fixed size blocks, make sure they are not 512 bytes. This
606 is too small and the overhead that Bacula has with each record will become
607 excessive. If at all possible set any fixed block size to something like
608 64,512 bytes or possibly 32,768 if 64,512 is too large for your drive. See
609 below for the details on checking and setting the default drive block size.
611 To recover files from tapes written in fixed block mode, see below.
614 \subsubsection*{Ensuring that the Tape Modes Are Properly Set -- {\bf Linux
616 \index[general]{Ensuring that the Tape Modes Are Properly Set -- Linux Only}
617 \index[general]{Only!Ensuring that the Tape Modes Are Properly Set -- Linux}
618 \addcontentsline{toc}{subsubsection}{Ensuring that the Tape Modes Are Properly
621 If you have a modern SCSI tape drive and you are having problems with the {\bf
622 test} command as noted above, it may be that some program has set one or more
623 of your SCSI driver's options to non-default values. For example, if your
624 driver is set to work in SysV manner, Bacula will not work correctly because
625 it expects BSD behavior. To reset your tape drive to the default values, you
626 can try the following, but {\bf ONLY} if you have a SCSI tape drive on a {\bf
632 mt -f /dev/nst0 rewind
633 mt -f /dev/nst0 stoptions buffer-writes async-writes read-ahead
637 The above commands will clear all options and then set those specified. None
638 of the specified options are required by Bacula, but a number of other options
639 such as SysV behavior must not be set. Bacula does not support SysV tape
640 behavior. On systems other than Linux, you will need to consult your {\bf mt}
641 man pages or documentation to figure out how to do the same thing. This should
642 not really be necessary though -- for example, on both Linux and Solaris
643 systems, the default tape driver options are compatible with Bacula.
644 On Solaris systems, you must take care to specify the correct device
645 name on the {\bf Archive device} directive. See above for more details.
647 You may also want to ensure that no prior program has set the default block
648 size, as happened to one user, by explicitly turning it off with:
652 mt -f /dev/nst0 defblksize 0
656 If you would like to know what options you have set before making any of the
657 changes noted above, you can now view them on Linux systems, thanks to a tip
658 provided by Willem Riede. Do the following:
663 mt -f /dev/nst0 stsetoptions 0
664 grep st0 /var/log/messages
668 and you will get output that looks something like the following:
672 kernel: st0: Mode 0 options: buffer writes: 1, async writes: 1, read ahead: 1
673 kernel: st0: can bsr: 0, two FMs: 0, fast mteom: 0, auto lock: 0,
674 kernel: st0: defs for wr: 0, no block limits: 0, partitions: 0, s2 log: 0
675 kernel: st0: sysv: 0 nowait: 0
679 Note, I have chopped off the beginning of the line with the date and machine
680 name for presentation purposes.
682 Some people find that the above settings only last until the next reboot, so
683 please check this otherwise you may have unexpected problems.
685 Beginning with Bacula version 1.35.8, if Bacula detects that you are running
686 in variable block mode, it will attempt to set your drive appropriately. All
687 OSes permit setting variable block mode, but some OSes do not permit setting
688 the other modes that Bacula needs to function properly.
691 \subsubsection*{Checking and Setting Tape Hardware Compression and Blocking
693 \index[general]{Checking and Setting Tape Hardware Compression and Blocking
695 \index[general]{Size!Checking and Setting Tape Hardware Compression and
697 \addcontentsline{toc}{subsubsection}{Checking and Setting Tape Hardware
698 Compression and Blocking Size}
700 As far as I can tell, there is no way with the {\bf mt} program to check if
701 your tape hardware compression is turned on or off. You can, however, turn it
702 on by using (on Linux):
707 mt -f /dev/nst0 defcompression 1
711 and of course, if you use a zero instead of the one at the end, you will turn
714 If you have built the {\bf mtx} program in the {\bf depkgs} package, you can
715 use tapeinfo to get quite a bit of information about your tape drive even if
716 it is not an autochanger. This program is called using the SCSI control
717 device. On Linux for tape drive /dev/nst0, this is usually /dev/sg0, while on
718 FreeBSD for /dev/nsa0, the control device is often /dev/pass2. For example on
719 my DDS-4 drive (/dev/nst0), I get the following:
724 Product Type: Tape Drive
726 Product ID: 'C5713A '
735 Medium Type: Not Loaded
741 where the {\bf DataCompEnabled: yes} means that tape hardware compression is
742 turned on. You can turn it on and off (yes|no) by using the {\bf mt}
743 commands given above. Also, this output will tell you if the {\bf BlockSize}
744 is non-zero and hence set for a particular block size. Bacula is not likely to
745 work in such a situation because it will normally attempt to write blocks of
746 64,512 bytes, except the last block of the job which will generally be
747 shorter. The first thing to try is setting the default block size to zero
748 using the {\bf mt -f /dev/nst0 defblksize 0} command as shown above.
749 On FreeBSD, this would be something like: {\bf mt -f /dev/nsa0 blocksize 0}.
751 On some operating systems with some tape drives, the amount of data that
752 can be written to the tape and whether or not compression is enabled is
753 determined by the density usually the {\bf mt -f /dev/nst0 setdensity xxx} command.
754 Often {\bf mt -f /dev/nst0 status} will print out the current
755 density code that is used with the drive. Most systems, but unfortunately
756 not all, set the density to the maximum by default. On some systems, you
757 can also get a list of all available density codes with:
758 {\bf mt -f /dev/nst0 densities} or a similar {\bf mt} command.
759 Note, for DLT and SDLT devices, no-compression versus compression is very
760 often controlled by the density code. On FreeBSD systems, the compression
761 mode is set using {\bf mt -f /dev/nsa0 comp xxx} where xxx is the
762 mode you want. In general, see {\bf man mt} for the options available on
765 Note, some of the above {\bf mt} commands may not be persistent depending
766 on your system configuration. That is they may be reset if a program
767 other than Bacula uses the drive or, as is frequently the case, on reboot
770 If your tape drive requires fixed block sizes (very unusual), you can use the
775 Minimum Block Size = nnn
776 Maximum Block Size = nnn
780 in your Storage daemon's Device resource to force Bacula to write fixed size
781 blocks (where you sent nnn to be the same for both of the above records). This
782 should be done only if your drive does not support variable block sizes, or
783 you have some other strong reasons for using fixed block sizes. As mentioned
784 above, a small fixed block size of 512 or 1024 bytes will be very inefficient.
785 Try to set any fixed block size to something like 64,512 bytes or larger if
786 your drive will support it.
788 Also, note that the {\bf Medium Type} field of the output of {\bf tapeinfo}
789 reports {\bf Not Loaded}, which is not correct. As a consequence, you should
790 ignore that field as well as the {\bf Attached Changer} field.
792 To recover files from tapes written in fixed block mode, see below.
795 \subsubsection*{Tape Modes on FreeBSD}
796 \index[general]{FreeBSD!Tape Modes on}
797 \index[general]{Tape Modes on FreeBSD}
798 \addcontentsline{toc}{subsubsection}{Tape Modes on FreeBSD}
800 On most FreeBSD systems such as 4.9 and most tape drives, Bacula should run
805 mt -f /dev/nsa0 seteotmodel 2
806 mt -f /dev/nsa0 blocksize 0
807 mt -f /dev/nsa0 comp enable
811 You might want to put those commands in a startup script to make sure your
812 tape driver is properly initialized before running Bacula, because
813 depending on your system configuration, these modes may be reset if a
814 program other than Bacula uses the drive or when your system is rebooted.
816 Then according to what the {\bf btape test} command returns, you will probably
817 need to set the following (see below for an alternative):
821 Hardware End of Medium = no
823 Backward Space Record = no
824 Backward Space File = no
825 Fast Forward Space File = no
830 Then be sure to run some append tests with Bacula where you start and stop
831 Bacula between appending to the tape, or use {\bf btape} version 1.35.1 or
832 greater, which includes simulation of stopping/restarting Bacula.
834 Please see the file {\bf platforms/freebsd/pthreads-fix.txt} in the main
835 Bacula directory concerning {\bf important} information concerning
836 compatibility of Bacula and your system. A much more optimal Device
837 configuration is shown below, but does not work with all tape drives. Please
838 test carefully before putting either into production.
840 Note, for FreeBSD 4.10-RELEASE, using a Sony TSL11000 L100 DDS4 with an
841 autochanger set to variable block size and DCLZ compression, Brian McDonald
842 reports that to get Bacula to append correctly between Bacula executions,
843 the correct values to use are:
847 mt -f /dev/nsa0 seteotmodel 1
848 mt -f /dev/nsa0 blocksize 0
849 mt -f /dev/nsa0 comp enable
857 Hardware End of Medium = no
859 Backward Space Record = no
860 Backward Space File = no
861 Fast Forward Space File = yes
866 This has been confirmed by several other people using different hardware. This
867 configuration is the preferred one because it uses one EOF and no backspacing
868 at the end of the tape, which works much more efficiently and reliably with
871 Finally, here is a Device configuration that Danny Butroyd reports to work
872 correctly with the Overland Powerloader tape library using LT0-2 and
877 # Overland Powerloader LT02 - 17 slots single drive
881 Archive Device = /dev/nsa0
882 AutomaticMount = yes;
884 RemovableMedia = yes;
886 Changer Command = "/usr/local/sbin/mtx-changer %c %o %S %a %d"
887 Changer Device = /dev/pass2
889 Alert Command = "sh -c 'tapeinfo -f %c |grep TapeAlert|cat'"
891 # FreeBSD Specific Settings
892 Offline On Unmount = no
893 Hardware End of Medium = no
895 Backward Space Record = no
896 Fast Forward Space File = no
903 \subsubsection*{Determining What Tape Drives and Autochangers You Have on
905 \index[general]{FreeBSD!Determining What Tape Drives and Autochangers You Have
907 \index[general]{Determining What Tape Drives and Autochangers You Have on
909 \addcontentsline{toc}{subsubsection}{Determining What Tape Drives and
910 Autochangers You Have on FreeBSD}
912 On FreeBSD, you can do a {\bf camcontrol devlist} as root to determine what
913 drives and autochangers you have. For example,
917 undef# camcontrol devlist
918 at scbus0 target 2 lun 0 (pass0,sa0)
919 at scbus0 target 4 lun 0 (pass1,sa1)
920 at scbus0 target 4 lun 1 (pass2)
924 from the above, you can determine that there is a tape drive on {\bf /dev/sa0}
925 and another on {\bf /dev/sa1} in addition since there is a second line for the
926 drive on {\bf /dev/sa1}, you know can assume that it is the control device for
927 the autochanger (i.e. {\bf /dev/pass2}). It is also the control device name to
928 use when invoking the tapeinfo program. E.g.
932 tapeinfo -f /dev/pass2
938 \subsubsection*{Using the OnStream driver on Linux Systems}
939 \index[general]{Using the OnStream driver on Linux Systems}
940 \index[general]{Systems!Using the OnStream driver on Linux}
941 \addcontentsline{toc}{subsubsection}{Using the OnStream driver on Linux
944 Bacula version 1.33 (not 1.32x) is now working and ready for testing with the
945 OnStream kernel osst driver version 0.9.14 or above. Osst is available from:
946 \elink{http://sourceforge.net/projects/osst/}
947 {http://sourceforge.net/projects/osst/}.
949 To make Bacula work you must first load the new driver then, as root, do:
953 mt -f /dev/nosst0 defblksize 32768
957 Also you must add the following to your Device resource in your Storage
962 Minimum Block Size = 32768
963 Maximum Block Size = 32768
967 Here is a Device specification provided by Michel Meyers that is known to
973 Name = "Onstream DI-30"
974 Media Type = "ADR-30"
975 Archive Device = /dev/nosst0
976 Minimum Block Size = 32768
977 Maximum Block Size = 32768
978 Hardware End of Medium = yes
980 Backward Space File = yes
981 Fast Forward Space File = yes
985 Removable Media = yes
990 \subsection*{Hardware Compresson on EXB-8900}
991 \index[general]{Hardware Compression on EXB-8900}
992 \index[general]{EXB-8900!Hardware Compression}
993 \addcontentsline{to}{subsection}{Hardware Compression on EXB-8900}
994 To active, check, or disable the hardware compression feature
995 on an EXB-8900, use the exabyte MammothTool. You can get it here:
996 \elink{http://www.exabyte.com/support/online/downloads/index.cfm}
997 {http://www.exabyte.com/support/online/downloads/index.cfm}.
998 There is a solaris version of this tool. With option -C 0 or 1 you
999 can disable or activate compression. Start this tool without any
1000 options for a small reference.
1003 \subsubsection*{Using btape to Simulate Filling a Tape}
1004 \index[general]{Using btape to Simulate Filling a Tape}
1005 \index[general]{Tape!Using btape to Simulate Filling a}
1006 \addcontentsline{toc}{subsubsection}{Using btape to Simulate Filling a
1009 Because there are often problems with certain tape drives or systems when end
1010 of tape conditions occur, {\bf btape} has a special command {\bf fill} that
1011 causes it to write random data to a tape until the tape fills. It then writes
1012 at least one more Bacula block to a second tape. Finally, it reads back both
1013 tapes to ensure that the data has been written in a way that Bacula can
1014 recover it. Note, there is also a single tape option as noted below, which you
1015 should use rather than the two tape test. See below for more details.
1017 This can be an extremely time consuming process (here it is about 6 hours) to
1018 fill a full tape. Note, that btape writes random data to the tape when it is
1019 filling it. This has two consequences: 1. it takes a bit longer to generate
1020 the data, especially on slow CPUs. 2. the total amount of data is
1021 approximately the real physical capacity of your tape, regardless of whether
1022 or not the tape drive compression is on or off. This is because random data
1023 does not compress very much.
1025 To begin this test, you enter the {\bf fill} command and follow the
1026 instructions. There are two options: the simple single tape option and the
1027 multiple tape option. Please use only the simple single tape option because
1028 the multiple tape option still doesn't work totally correctly. If the single
1029 tape option does not succeed, you should correct the problem before using
1031 \label{RecoveringFiles}
1033 \subsection*{Recovering Files Written to Tape With Fixed Block Sizes}
1034 \index[general]{Recovering Files Written to Tape With Fixed Block Sizes}
1035 \index[general]{Sizes!Recovering Files Written to Tape With Fixed Block}
1036 \addcontentsline{toc}{subsection}{Recovering Files Written to Tape With Fixed
1039 If you have been previously running your tape drive in fixed block mode
1040 (default 512) and Bacula with variable blocks (default), then in version
1041 1.32f-x and 1.34 and above, Bacula will fail to recover files because it does
1042 block spacing, and because the block sizes don't agree between your tape drive
1043 and Bacula it will not work.
1045 The long term solution is to run your drive in variable block mode as
1046 described above. However, if you have written tapes using fixed block sizes,
1047 this can be a bit of a pain. The solution to the problem is: while you are
1048 doing a restore command using a tape written in fixed block size, ensure that
1049 your drive is set to the fixed block size used while the tape was written.
1050 Then when doing the {\bf restore} command in the Console program, do not
1051 answer the prompt {\bf yes/mod/no}. Instead, edit the bootstrap file (the
1052 location is listed in the prompt) using any ASCII editor. Remove all {\bf
1053 VolBlock} lines in the file. When the file is re-written, answer the question,
1054 and Bacula will run without using block positioning, and it should recover
1058 \subsection*{Tape Blocking Modes}
1059 \index[general]{Modes!Tape Blocking}
1060 \index[general]{Tape Blocking Modes}
1061 \addcontentsline{toc}{subsection}{Tape Blocking Modes}
1063 SCSI tapes may either be written in {\bf variable} or {\bf fixed} block sizes.
1064 Newer drives support both modes, but some drives such as the QIC devices
1065 always use fixed block sizes. Bacula attempts to fill and write complete
1066 blocks (default 65K), so that in normal mode (variable block size), Bacula
1067 will always write blocks of the same size except the last block of a Job. If
1068 Bacula is configured to write fixed block sizes, it will pad the last block of
1069 the Job to the correct size. Bacula expects variable tape block size drives to
1070 behave as follows: Each write to the drive results in a single record being
1071 written to the tape. Each read returns a single record. If you request less
1072 bytes than are in the record, only those number of bytes will be returned, but
1073 the entire logical record will have been read (the next read will retrieve the
1074 next record). Thus data from a single write is always returned in a single
1075 read, and sequentially written records are returned by sequential reads.
1077 Bacula expects fixed block size tape drives to behave as follows: If a write
1078 length is greater than the physical block size of the drive, the write will be
1079 written as two blocks each of the fixed physical size. This single write may
1080 become multiple physical records on the tape. (This is not a good situation).
1081 According to the documentation, one may never write an amount of data that is
1082 not the exact multiple of the blocksize (it is not specified if an error
1083 occurs or if the the last record is padded). When reading, it is my
1084 understanding that each read request reads one physical record from the tape.
1085 Due to the complications of fixed block size tape drives, you should avoid
1086 them if possible with Bacula, or you must be ABSOLUTELY certain that you use
1087 fixed block sizes within Bacula that correspond to the physical block size of
1088 the tape drive. This will ensure that Bacula has a one to one correspondence
1089 between what it writes and the physical record on the tape.
1091 Please note that Bacula will not function correctly if it writes a block and
1092 that block is split into two or more physical records on the tape. Bacula
1093 assumes that each write causes a single record to be written, and that it can
1094 sequentially recover each of the blocks it has written by using the same
1095 number of sequential reads as it had written.
1097 \subsection*{Details of Tape Modes}
1098 \index[general]{Modes!Details}
1099 \index[general]{Details of Tape Modes}
1100 \addcontentsline{toc}{subsection}{Details of Tape Modes}
1101 Rudolf Cejka has provided the following information concerning
1102 certain tape modes and MTEOM.
1106 It is always possible to position filemarks or blocks, whereas
1107 positioning to the end-of-data is only optional feature, however it is
1108 implemented very often. SCSI specification also talks about optional
1109 sequential filemarks, setmarks and sequential setmarks, but these are not
1110 implemented so often. Modern tape drives keep track of file positions in
1111 built-in chip (AIT, LTO) or at the beginning of the tape (SDLT), so there
1112 is not any speed difference, if end-of-data or filemarks is used (I have
1113 heard, that LTO-1 from all 3 manufacturers do not use its chip for file
1114 locations, but a tape as in SDLT case, and I'm not sure about LTO-2 and
1115 LTO-3 case). However there is a big difference, that end-of-data ignores
1116 file position, whereas filemarks returns the real number of skipped
1117 files, so OS can track current file number just in filemarks case.
1120 Solaris does use just SCSI SPACE Filemarks, it does not support SCSI
1121 SPACE End-of-data. When MTEOM is called, Solaris does use SCSI SPACE
1122 Filemarks with count = 1048576 for fast mode, and combination of SCSI
1123 SPACE Filemarks with count = 1 with SCSI SPACE Blocks with count = 1 for
1124 slow mode, so EOD mark on the tape on some older tape drives is not
1125 skipped. File number is always tracked for MTEOM.
1127 Linux does support both SCSI SPACE Filemarks and End-of-data: When MTEOM
1128 is called in MT_ST_FAST_MTEOM mode, SCSI SPACE End-of-data is used.
1129 In the other case, SCSI SPACE Filemarks with count =
1131 There is no real slow mode like in Solaris - I just expect, that for
1132 older tape drives Filemarks may be slower than End-of-data, but not so
1133 much as in Solaris slow mode. File number is tracked for MTEOM just
1134 without MT_ST_FAST_MTEOM - when MT_ST_FAST_MTEOM is used, it is not.
1136 FreeBSD does support both SCSI SPACE Filemarks and End-of-data, but when
1137 MTEOD (MTEOM) is called, SCSI SPACE End-of-data is always used. FreeBSD
1138 never use SCSI SPACE Filemarks for MTEOD. File number is never tracked
1142 When {\bf Hardware End of Medium = Yes} is used, MTEOM is called, but it
1143 does not mean, that hardware End-of-data must be used. When Hardware End
1144 of Medium = No, if Fast Forward Space File = Yes, MTFSF with count =
1145 32767 is used, else Block Read with count = 1 with Forward Space File
1146 with count = 1 is used, which is really very slow.
1148 \item [Hardware End of Medium = Yes|No]
1149 The name of this option is misleading and is the source of confusion,
1150 because it is not the hardware EOM, what is really switched here.
1152 If I use Yes, OS must not use SCSI SPACE End-of-data, because Bacula
1153 expects, that there is tracked file number, which is not supported by
1154 SCSI specification. Instead, the OS have to use SCSI SPACE Filemarks.
1156 If I use No, an action depends on Fast Forward Space File.
1158 When I set {\bf Hardware End of Medium = no}
1159 and {\bf Fast Forward Space File = no}
1160 file positioning was very slow
1161 on my LTO-3 (about 10 to 100 minutes), but
1163 with {\bf Hardware End of Medium = no} and
1164 {\bf Fast Forward Space File = yes}, the time is 10 to
1165 100 times faster (about 1 to 2 minutes).
1169 \subsection*{Autochanger Errors}
1170 \index[general]{Errors!Autochanger}
1171 \index[general]{Autochanger Errors}
1172 \addcontentsline{toc}{subsection}{Autochanger Errors}
1174 If you are getting errors such as:
1178 3992 Bad autochanger "load slot 1, drive 1": ERR=Child exited with code 1.
1182 and you are running your Storage daemon as non-root, then most likely
1183 you are having permissions problems with the control channel. Running
1184 as root, set permissions on /dev/sgX so that the userid and group of
1185 your Storage daemon can access the device. You need to ensure that you
1186 all access to the proper control device, and if you don't have any
1187 SCSI disk drives (including SATA drives), you might want to change
1188 the permissions on /dev/sg*.