--- /dev/null
+%%
+%%
+
+\chapter{Testing Your Tape Drive With Bacula}
+\label{TapeTestingChapter}
+\index[general]{Testing Your Tape Drive With Bacula}
+
+This chapter is concerned with testing and configuring your tape drive to make
+sure that it will work properly with Bacula using the {\bf btape} program.
+\label{summary}
+
+\section{Get Your Tape Drive Working}
+
+In general, you should follow the following steps to get your tape drive to
+work with Bacula. Start with a tape mounted in your drive. If you have an
+autochanger, load a tape into the drive. We use {\bf /dev/nst0} as the tape
+drive name, you will need to adapt it according to your system.
+
+Do not proceed to the next item until you have succeeded with the previous
+one.
+
+\begin{enumerate}
+\item Make sure that Bacula (the Storage daemon) is not running
+ or that you have {\bf unmount}ed the drive you will use
+ for testing.
+
+\item Use tar to write to, then read from your drive:
+
+ \footnotesize
+\begin{verbatim}
+ mt -f /dev/nst0 rewind
+ tar cvf /dev/nst0 .
+ mt -f /dev/nst0 rewind
+ tar tvf /dev/nst0
+
+\end{verbatim}
+\normalsize
+
+\item Make sure you have a valid and correct Device resource corresponding
+ to your drive. For Linux users, generally, the default one works. For
+ FreeBSD users, there are two possible Device configurations (see below).
+ For other drives and/or OSes, you will need to first ensure that your
+ system tape modes are properly setup (see below), then possibly modify
+ you Device resource depending on the output from the btape program (next
+ item). When doing this, you should consult the \ilink{Storage Daemon
+ Configuration}{StoredConfChapter} of this manual.
+
+\item If you are using a Fibre Channel to connect your tape drive to
+ Bacula, please be sure to disable any caching in the NSR (network
+ storage router, which is a Fibre Channel to SCSI converter).
+
+\item Run the btape {\bf test} command:
+
+ \footnotesize
+\begin{verbatim}
+ ./btape -c bacula-sd.conf /dev/nst0
+ test
+
+\end{verbatim}
+\normalsize
+
+ It isn't necessary to run the autochanger part of the test at this time,
+ but do not go past this point until the basic test succeeds. If you do
+ have an autochanger, please be sure to read the \ilink{Autochanger
+ chapter}{AutochangersChapter} of this manual.
+
+\item Run the btape {\bf fill} command, preferably with two volumes. This
+ can take a long time. If you have an autochanger and it is configured, Bacula
+ will automatically use it. If you do not have it configured, you can manually
+ issue the appropriate {\bf mtx} command, or press the autochanger buttons to
+ change the tape when requested to do so.
+
+\item FreeBSD users, if you have a pre-5.0 system run the {\bf tapetest}
+ program, and make sure your system is patched if necessary. The tapetest
+ program can be found in the platform/freebsd directory. The instructions
+ for its use are at the top of the file.
+
+\item Run Bacula, and backup a reasonably small directory, say 60
+ Megabytes. Do three successive backups of this directory.
+
+\item Stop Bacula, then restart it. Do another full backup of the same
+ directory. Then stop and restart Bacula.
+
+\item Do a restore of the directory backed up, by entering the following
+ restore command, being careful to restore it to an alternate location:
+
+
+\footnotesize
+\begin{verbatim}
+ restore select all done
+ yes
+
+\end{verbatim}
+\normalsize
+
+ Do a {\bf diff} on the restored directory to ensure it is identical to the
+ original directory. If you are going to backup multiple different systems
+ (Linux, Windows, Mac, Solaris, FreeBSD, ...), be sure you test the restore
+ on each system type.
+
+\item If you have an autochanger, you should now go back to the btape program
+ and run the autochanger test:
+
+\footnotesize
+\begin{verbatim}
+ ./btape -c bacula-sd.conf /dev/nst0
+ auto
+
+\end{verbatim}
+\normalsize
+
+ Adjust your autochanger as necessary to ensure that it works correctly. See
+ the Autochanger chapter of this manual for a complete discussion of testing
+ your autochanger.
+
+\item We strongly recommend that you use a dedicated SCSI
+ controller for your tape drives. Scanners are known to induce
+ serious problems with the SCSI bus, causing it to reset. If the
+ SCSI bus is reset while Bacula has the tape drive open, it will
+ most likely be fatal to your tape since the drive will rewind.
+ These kinds of problems show up in the system log. For example,
+ the following was most likely caused by a scanner:
+
+\footnotesize
+\begin{verbatim}
+Feb 14 17:29:55 epohost kernel: (scsi0:A:2:0): No or incomplete CDB sent to device.
+Feb 14 17:29:55 epohost kernel: scsi0: Issued Channel A Bus Reset. 1 SCBs aborted
+\end{verbatim}
+\normalsize
+
+\end{enumerate}
+
+If you have reached this point, you stand a good chance of having everything
+work. If you get into trouble at any point, {\bf carefully} read the
+documentation given below. If you cannot get past some point, ask the {\bf
+bacula-users} email list, but specify which of the steps you have successfully
+completed. In particular, you may want to look at the
+\ilink{ Tips for Resolving Problems}{problems1} section below.
+
+
+\label{NoTapeInDrive}
+\subsection{Problems When no Tape in Drive}
+\index[general]{Problems When no Tape in Drive}
+When Bacula was first written the Linux 2.4 kernel permitted opening the
+drive whether or not there was a tape in the drive. Thus the Bacula code is
+based on the concept that if the drive cannot be opened, there is a serious
+problem, and the job is failed.
+
+With version 2.6 of the Linux kernel, if there is no tape in the drive, the
+OS will wait two minutes (default) and then return a failure, and consequently,
+Bacula version 1.36 and below will fail the job. This is important to keep
+in mind, because if you use an option such as {\bf Offline on Unmount =
+yes}, there will be a point when there is no tape in the drive, and if
+another job starts or if Bacula asks the operator to mount a tape, when
+Bacula attempts to open the drive (about a 20 minute delay), it will fail
+and Bacula will fail the job.
+
+In version 1.38.x, the Bacula code partially gets around this problem -- at
+least in the initial open of the drive. However, functions like Polling
+the drive do not work correctly if there is no tape in the drive.
+Providing you do not use {\bf Offline on Unmount = yes}, you should not
+experience job failures as mentioned above. If you do experience such
+failures, you can also increase the {\bf Maximum Open Wait} time interval,
+which will give you more time to mount the next tape before the job is
+failed.
+
+\subsection{Specifying the Configuration File}
+\index[general]{File!Specifying the Configuration}
+\index[general]{Specifying the Configuration File}
+
+Starting with version 1.27, each of the tape utility programs including the
+{\bf btape} program requires a valid Storage daemon configuration file
+(actually, the only part of the configuration file that {\bf btape} needs is
+the {\bf Device} resource definitions). This permits {\bf btape} to find the
+configuration parameters for your archive device (generally a tape drive).
+Without those parameters, the testing and utility programs do not know how to
+properly read and write your drive. By default, they use {\bf bacula-sd.conf}
+in the current directory, but you may specify a different configuration file
+using the {\bf -c} option.
+
+\subsection{Specifying a Device Name For a Tape}
+\index[general]{Tape!Specifying a Device Name For a}
+\index[general]{Specifying a Device Name For a Tape}
+
+{\bf btape} {\bf device-name} where the Volume can be found. In the case of a
+tape, this is the physical device name such as {\bf /dev/nst0} or {\bf
+/dev/rmt/0ubn} depending on your system that you specify on the Archive Device
+directive. For the program to work, it must find the identical name in the
+Device resource of the configuration file. If the name is not found in the
+list of physical names, the utility program will compare the name you entered
+to the Device names (rather than the Archive device names).
+
+When specifying a tape device, it is preferable that the "non-rewind"
+variant of the device file name be given. In addition, on systems such as
+Sun, which have multiple tape access methods, you must be sure to specify
+to use Berkeley I/O conventions with the device. The
+{\bf b} in the Solaris (Sun) archive specification {\bf /dev/rmt/0mbn} is
+what is needed in this case. Bacula does not support SysV tape drive
+behavior.
+
+See below for specifying Volume names.
+
+\subsection{Specifying a Device Name For a File}
+\index[general]{File!Specifying a Device Name For a}
+\index[general]{Specifying a Device Name For a File}
+
+If you are attempting to read or write an archive file rather than a tape, the
+{\bf device-name} should be the full path to the archive location including
+the filename. The filename (last part of the specification) will be stripped
+and used as the Volume name, and the path (first part before the filename)
+must have the same entry in the configuration file. So, the path is equivalent
+to the archive device name, and the filename is equivalent to the volume name.
+
+
+\section{btape}
+\label{btape1}
+\index[general]{Btape}
+
+This program permits a number of elementary tape operations via a tty command
+interface. The {\bf test} command, described below, can be very useful for
+testing tape drive compatibility problems. Aside from initial testing of tape
+drive compatibility with {\bf Bacula}, {\bf btape} will be mostly used by
+developers writing new tape drivers.
+
+{\bf btape} can be dangerous to use with existing {\bf Bacula} tapes because
+it will relabel a tape or write on the tape if so requested regardless of
+whether or not the tape contains valuable data, so please be careful and use
+it only on blank tapes.
+
+To work properly, {\bf btape} needs to read the Storage daemon's configuration
+file. As a default, it will look for {\bf bacula-sd.conf} in the current
+directory. If your configuration file is elsewhere, please use the {\bf -c}
+option to specify where.
+
+The physical device name or the Device resource name must be specified on the
+command line, and this same device name must be present in the Storage
+daemon's configuration file read by {\bf btape}
+
+\footnotesize
+\begin{verbatim}
+Usage: btape [options] device_name
+ -b <file> specify bootstrap file
+ -c <file> set configuration file to file
+ -d <nn> set debug level to nn
+ -p proceed inspite of I/O errors
+ -s turn off signals
+ -v be verbose
+ -? print this message.
+\end{verbatim}
+\normalsize
+
+\subsection{Using btape to Verify your Tape Drive}
+\index[general]{Using btape to Verify your Tape Drive}
+\index[general]{Drive!Using btape to Verify your Tape}
+
+An important reason for this program is to ensure that a Storage daemon
+configuration file is defined so that Bacula will correctly read and write
+tapes.
+
+It is highly recommended that you run the {\bf test} command before running
+your first Bacula job to ensure that the parameters you have defined for your
+storage device (tape drive) will permit {\bf Bacula} to function properly. You
+only need to mount a blank tape, enter the command, and the output should be
+reasonably self explanatory. For example:
+
+\footnotesize
+\begin{verbatim}
+(ensure that Bacula is not running)
+./btape -c /usr/bin/bacula/bacula-sd.conf /dev/nst0
+\end{verbatim}
+\normalsize
+
+The output will be:
+
+\footnotesize
+\begin{verbatim}
+Tape block granularity is 1024 bytes.
+btape: btape.c:376 Using device: /dev/nst0
+*
+\end{verbatim}
+\normalsize
+
+Enter the test command:
+
+\footnotesize
+\begin{verbatim}
+test
+\end{verbatim}
+\normalsize
+
+The output produced should be something similar to the following: I've cut the
+listing short because it is frequently updated to have new tests.
+
+\footnotesize
+\begin{verbatim}
+=== Append files test ===
+This test is essential to Bacula.
+I'm going to write one record in file 0,
+ two records in file 1,
+ and three records in file 2
+btape: btape.c:387 Rewound /dev/nst0
+btape: btape.c:855 Wrote one record of 64412 bytes.
+btape: btape.c:857 Wrote block to device.
+btape: btape.c:410 Wrote EOF to /dev/nst0
+btape: btape.c:855 Wrote one record of 64412 bytes.
+btape: btape.c:857 Wrote block to device.
+btape: btape.c:855 Wrote one record of 64412 bytes.
+btape: btape.c:857 Wrote block to device.
+btape: btape.c:410 Wrote EOF to /dev/nst0
+btape: btape.c:855 Wrote one record of 64412 bytes.
+btape: btape.c:857 Wrote block to device.
+btape: btape.c:855 Wrote one record of 64412 bytes.
+btape: btape.c:857 Wrote block to device.
+btape: btape.c:855 Wrote one record of 64412 bytes.
+btape: btape.c:857 Wrote block to device.
+btape: btape.c:410 Wrote EOF to /dev/nst0
+btape: btape.c:387 Rewound /dev/nst0
+btape: btape.c:693 Now moving to end of media.
+btape: btape.c:427 Moved to end of media
+We should be in file 3. I am at file 3. This is correct!
+Now the important part, I am going to attempt to append to the tape.
+...
+=== End Append files test ===
+\end{verbatim}
+\normalsize
+
+If you do not successfully complete the above test, please resolve the
+problem(s) before attempting to use {\bf Bacula}. Depending on your tape
+drive, the test may recommend that you add certain records to your
+configuration. We strongly recommend that you do so and then re-run the above
+test to insure it works the first time.
+
+Some of the suggestions it provides for resolving the problems may or may not
+be useful. If at all possible avoid using fixed blocking. If the test suddenly
+starts to print a long series of:
+
+\footnotesize
+\begin{verbatim}
+Got EOF on tape.
+Got EOF on tape.
+...
+\end{verbatim}
+\normalsize
+
+then almost certainly, you are running your drive in fixed block mode rather
+than variable block mode. See below for more help of resolving fix
+versus variable block problems.
+
+It is also possible that you have your drive
+set in SysV tape drive mode. The drive must use BSD tape conventions.
+See the section above on setting your {\bf Archive device} correctly.
+
+For FreeBSD users, please see the notes below for doing further testing of
+your tape drive.
+
+\subsection{Testing tape drive speed}
+\label{sec:btapespeed}
+
+To determine the best configuration of your tape drive, you can run the
+\texttt{speed} command available in the \texttt{btape} program.
+
+This command can have the following arguments:
+\begin{itemize}
+\item[\texttt{file\_size=n}] Specify the Maximum File Size for this test
+ (between 1 and 5GB). This counter is in GB.
+\item[\texttt{nb\_file=n}] Specify the number of file to be written. The amount
+ of data should be greater than your memory ($file\_size*nb\_file$).
+\item[\texttt{skip\_zero}] This flag permits to skip tests with constant
+ data.
+\item[\texttt{skip\_random}] This flag permits to skip tests with random
+ data.
+\item[\texttt{skip\_raw}] This flag permits to skip tests with raw access.
+\item[\texttt{skip\_block}] This flag permits to skip tests with Bacula block
+ access.
+\end{itemize}
+
+\begin{verbatim}
+*speed file_size=3 skip_raw
+btape.c:1078 Test with zero data and bacula block structure.
+btape.c:956 Begin writing 3 files of 3.221 GB with blocks of 129024 bytes.
+++++++++++++++++++++++++++++++++++++++++++
+btape.c:604 Wrote 1 EOF to "Drive-0" (/dev/nst0)
+btape.c:406 Volume bytes=3.221 GB. Write rate = 44.128 MB/s
+...
+btape.c:383 Total Volume bytes=9.664 GB. Total Write rate = 43.531 MB/s
+
+btape.c:1090 Test with random data, should give the minimum throughput.
+btape.c:956 Begin writing 3 files of 3.221 GB with blocks of 129024 bytes.
++++++++++++++++++++++++++++++++++++++++++++
+btape.c:604 Wrote 1 EOF to "Drive-0" (/dev/nst0)
+btape.c:406 Volume bytes=3.221 GB. Write rate = 7.271 MB/s
++++++++++++++++++++++++++++++++++++++++++++
+...
+btape.c:383 Total Volume bytes=9.664 GB. Total Write rate = 7.365 MB/s
+
+\end{verbatim}
+
+When using compression, the random test will give your the minimum throughput
+of your drive . The test using constant string will give you the maximum speed
+of your hardware chain. (cpu, memory, scsi card, cable, drive, tape).
+
+You can change the block size in the Storage Daemon configuration file.
+
+\label{SCSITricks}
+\subsection{Linux SCSI Tricks}
+\index[general]{Tricks!Linux SCSI}
+\index[general]{Linux SCSI Tricks}
+
+You can find out what SCSI devices you have by doing:
+
+\footnotesize
+\begin{verbatim}
+lsscsi
+\end{verbatim}
+\normalsize
+
+Typical output is:
+
+\footnotesize
+\begin{verbatim}
+[0:0:0:0] disk ATA ST3160812AS 3.AD /dev/sda
+[2:0:4:0] tape HP Ultrium 2-SCSI F6CH /dev/st0
+[2:0:5:0] tape HP Ultrium 2-SCSI F6CH /dev/st1
+[2:0:6:0] mediumx OVERLAND LXB 0107 -
+[2:0:9:0] tape HP Ultrium 1-SCSI E50H /dev/st2
+[2:0:10:0] mediumx OVERLAND LXB 0107 -
+\end{verbatim}
+\normalsize
+
+There are two drives in one autochanger: /dev/st0 and /dev/st1
+and a third tape drive at /dev/st2. For using them with Bacula, one
+would normally reference them as /dev/nst0 ... /dev/nst2. Not also,
+there are two different autochangers identified as "mediumx OVERLAND LXB".
+They can be addressed via their /dev/sgN designation, which can be
+obtained by counting from the beginning as 0 to each changer. In the
+above case, the two changers are located on /dev/sg3 and /dev/sg5. The one
+at /dev/sg3, controls drives /dev/nst0 and /dev/nst1; and the one at
+/dev/sg5 controles drive /dev/nst2.
+
+If you do not have the {\bf lsscsi} command, you can obtain the same
+information as follows:
+
+\footnotesize
+\begin{verbatim}
+cat /proc/scsi/scsi
+\end{verbatim}
+\normalsize
+
+For the above example with the three drives and two autochangers,
+I get:
+
+\footnotesize
+\begin{verbatim}
+Attached devices:
+Host: scsi0 Channel: 00 Id: 00 Lun: 00
+ Vendor: ATA Model: ST3160812AS Rev: 3.AD
+ Type: Direct-Access ANSI SCSI revision: 05
+Host: scsi2 Channel: 00 Id: 04 Lun: 00
+ Vendor: HP Model: Ultrium 2-SCSI Rev: F6CH
+ Type: Sequential-Access ANSI SCSI revision: 03
+Host: scsi2 Channel: 00 Id: 05 Lun: 00
+ Vendor: HP Model: Ultrium 2-SCSI Rev: F6CH
+ Type: Sequential-Access ANSI SCSI revision: 03
+Host: scsi2 Channel: 00 Id: 06 Lun: 00
+ Vendor: OVERLAND Model: LXB Rev: 0107
+ Type: Medium Changer ANSI SCSI revision: 02
+Host: scsi2 Channel: 00 Id: 09 Lun: 00
+ Vendor: HP Model: Ultrium 1-SCSI Rev: E50H
+ Type: Sequential-Access ANSI SCSI revision: 03
+Host: scsi2 Channel: 00 Id: 10 Lun: 00
+ Vendor: OVERLAND Model: LXB Rev: 0107
+ Type: Medium Changer ANSI SCSI revision: 02
+\end{verbatim}
+\normalsize
+
+
+As an additional example, I get the following (on a different machine from the
+above example):
+
+\footnotesize
+\begin{verbatim}
+Attached devices:
+Host: scsi2 Channel: 00 Id: 01 Lun: 00
+ Vendor: HP Model: C5713A Rev: H107
+ Type: Sequential-Access ANSI SCSI revision: 02
+Host: scsi2 Channel: 00 Id: 04 Lun: 00
+ Vendor: SONY Model: SDT-10000 Rev: 0110
+ Type: Sequential-Access ANSI SCSI revision: 02
+\end{verbatim}
+\normalsize
+
+The above represents first an autochanger and second a simple
+tape drive. The HP changer (the first entry) uses the same SCSI channel
+for data and for control, so in Bacula, you would use:
+\footnotesize
+\begin{verbatim}
+Archive Device = /dev/nst0
+Changer Device = /dev/sg0
+\end{verbatim}
+\normalsize
+
+If you want to remove the SDT-10000 device, you can do so as root with:
+
+\footnotesize
+\begin{verbatim}
+echo "scsi remove-single-device 2 0 4 0">/proc/scsi/scsi
+\end{verbatim}
+\normalsize
+
+and you can put add it back with:
+
+\footnotesize
+\begin{verbatim}
+echo "scsi add-single-device 2 0 4 0">/proc/scsi/scsi
+\end{verbatim}
+\normalsize
+
+where the 2 0 4 0 are the Host, Channel, Id, and Lun as seen on the output
+from {\bf cat /proc/scsi/scsi}. Note, the Channel must be specified as
+numeric.
+
+Below is a slightly more complicated output, which is a single autochanger
+with two drives, and which operates the changer on a different channel
+from from the drives:
+
+\footnotesize
+\begin{verbatim}
+Attached devices:
+Host: scsi0 Channel: 00 Id: 00 Lun: 00
+ Vendor: ATA Model: WDC WD1600JD-75H Rev: 08.0
+ Type: Direct-Access ANSI SCSI revision: 05
+Host: scsi2 Channel: 00 Id: 04 Lun: 00
+ Vendor: HP Model: Ultrium 2-SCSI Rev: F6CH
+ Type: Sequential-Access ANSI SCSI revision: 03
+Host: scsi2 Channel: 00 Id: 05 Lun: 00
+ Vendor: HP Model: Ultrium 2-SCSI Rev: F6CH
+ Type: Sequential-Access ANSI SCSI revision: 03
+Host: scsi2 Channel: 00 Id: 06 Lun: 00
+ Vendor: OVERLAND Model: LXB Rev: 0106
+ Type: Medium Changer ANSI SCSI revision: 02
+\end{verbatim}
+\normalsize
+
+The above tape drives are accessed on /dev/nst0 and /dev/nst1, while
+the control channel for those two drives is /dev/sg3.
+
+
+
+\label{problems1}
+\section{Tips for Resolving Problems}
+\index[general]{Problems!Tips for Resolving}
+\index[general]{Tips for Resolving Problems}
+
+\label{CannotRestore}
+\subsection{Bacula Saves But Cannot Restore Files}
+\index[general]{Files!Bacula Saves But Cannot Restore}
+\index[general]{Bacula Saves But Cannot Restore Files}
+
+If you are getting error messages such as:
+
+\footnotesize
+\begin{verbatim}
+Volume data error at 0:1! Wanted block-id: "BB02", got "". Buffer discarded
+\end{verbatim}
+\normalsize
+
+It is very likely that Bacula has tried to do block positioning and ended up
+at an invalid block. This can happen if your tape drive is in fixed block mode
+while Bacula's default is variable blocks. Note that in such cases, Bacula is
+perfectly able to write to your Volumes (tapes), but cannot position to read
+them.
+
+There are two possible solutions.
+
+\begin{enumerate}
+\item The first and best is to always ensure that your drive is in variable
+ block mode. Note, it can switch back to fixed block mode on a reboot or if
+ another program uses the drive. So on such systems you need to modify the
+ Bacula startup files to explicitly set:
+
+\footnotesize
+\begin{verbatim}
+mt -f /dev/nst0 defblksize 0
+\end{verbatim}
+\normalsize
+
+or whatever is appropriate on your system. Note, if you are running a Linux
+system, and the above command does not work, it is most likely because you
+have not loaded the appropriate {\bf mt} package, which is often called
+{\bf mt\_st}, but may differ according to your distribution.
+
+\item The second possibility, especially, if Bacula wrote while the drive was
+ in fixed block mode, is to turn off block positioning in Bacula. This is done
+ by adding:
+
+\footnotesize
+\begin{verbatim}
+Block Positioning = no
+\end{verbatim}
+\normalsize
+
+to the Device resource. This is not the recommended procedure because it can
+enormously slow down recovery of files, but it may help where all else
+fails. This directive is available in version 1.35.5 or later (and not yet
+tested).
+\end{enumerate}
+
+If you are getting error messages such as:
+\footnotesize
+\begin{verbatim}
+Volume data error at 0:0!
+Block checksum mismatch in block=0 len=32625 calc=345678 blk=123456
+\end{verbatim}
+\normalsize
+
+You are getting tape read errors, and this is most likely due to
+one of the following things:
+\begin{enumerate}
+\item An old or bad tape.
+\item A dirty drive that needs cleaning (particularly for DDS drives).
+\item A loose SCSI cable.
+\item Old firmware in your drive. Make sure you have the latest firmware
+ loaded.
+\item Computer memory errors.
+\item Over-clocking your CPU.
+\item A bad SCSI card.
+\end{enumerate}
+
+
+\label{opendevice}
+\subsection{Bacula Cannot Open the Device}
+\index[general]{Device!Bacula Cannot Open the}
+\index[general]{Bacula Cannot Open the Device}
+
+If you get an error message such as:
+
+\footnotesize
+\begin{verbatim}
+dev open failed: dev.c:265 stored: unable to open
+device /dev/nst0:> ERR=No such device or address
+\end{verbatim}
+\normalsize
+
+the first time you run a job, it is most likely due to the fact that you
+specified the incorrect device name on your {\bf Archive Device}.
+
+If Bacula works fine with your drive, then all off a sudden you get error
+messages similar to the one shown above, it is quite possible that your driver
+module is being removed because the kernel deems it idle. This is done via
+{\bf crontab} with the use of {\bf rmmod -a}. To fix the problem, you can
+remove this entry from {\bf crontab}, or you can manually {\bf modprob} your
+driver module (or add it to the local startup script). Thanks to Alan Brown
+for this tip.
+\label{IncorrectFiles}
+
+\subsection{Incorrect File Number}
+\index[general]{Number!Incorrect File}
+\index[general]{Incorrect File Number}
+
+When Bacula moves to the end of the medium, it normally uses the {\bf
+ioctl(MTEOM)} function. Then Bacula uses the {\bf ioctl(MTIOCGET)} function to
+retrieve the current file position from the {\bf mt\_fileno} field. Some SCSI
+tape drivers will use a fast means of seeking to the end of the medium and in
+doing so, they will not know the current file position and hence return a {\bf
+-1}. As a consequence, if you get {\bf "This is NOT correct!"} in the
+positioning tests, this may be the cause. You must correct this condition in
+order for Bacula to work.
+
+There are two possible solutions to the above problem of incorrect file
+number:
+
+\begin{itemize}
+\item Figure out how to configure your SCSI driver to keep track of the file
+ position during the MTEOM request. This is the preferred solution.
+\item Modify the {\bf Device} resource of your {\bf bacula-sd.conf} file to
+ include:
+
+\footnotesize
+\begin{verbatim}
+Hardware End of File = no
+\end{verbatim}
+\normalsize
+
+This will cause Bacula to use the MTFSF request to seek to the end of the
+medium, and Bacula will keep track of the file number itself.
+\end{itemize}
+
+\label{IncorrectBlocks}
+\subsection{Incorrect Number of Blocks or Positioning Errors}
+\index[general]{Testing!Incorrect Number of Blocks or Positioning Errors}
+\index[general]{Incorrect Number of Blocks or Positioning Errors}
+
+{\bf Bacula's} preferred method of working with tape drives (sequential
+devices) is to run in variable block mode, and this is what is set by default.
+You should first ensure that your tape drive is set for variable block mode
+(see below).
+
+If your tape drive is in fixed block mode and you have told Bacula to use
+different fixed block sizes or variable block sizes (default), you will get
+errors when Bacula attempts to forward space to the correct block (the kernel
+driver's idea of tape blocks will not correspond to Bacula's).
+
+All modern tape drives support variable tape blocks, but some older drives (in
+particular the QIC drives) as well as the ATAPI ide-scsi driver run only in
+fixed block mode. The Travan tape drives also apparently must run in fixed
+block mode (to be confirmed).
+
+Even in variable block mode, with the exception of the first record on the
+second or subsequent volume of a multi-volume backup, Bacula will write blocks
+of a fixed size. However, in reading a tape, Bacula will assume that for each
+read request, exactly one block from the tape will be transferred. This the
+most common way that tape drives work and is well supported by {\bf Bacula}.
+
+Drives that run in fixed block mode can cause serious problems for Bacula if
+the drive's block size does not correspond exactly to {\bf Bacula's} block
+size. In fixed block size mode, drivers may transmit a partial block or
+multiple blocks for a single read request. From {\bf Bacula's} point of view,
+this destroys the concept of tape blocks. It is much better to run in variable
+block mode, and almost all modern drives (the OnStream is an exception) run in
+variable block mode. In order for Bacula to run in fixed block mode, you must
+include the following records in the Storage daemon's Device resource
+definition:
+
+\footnotesize
+\begin{verbatim}
+Minimum Block Size = nnn
+Maximum Block Size = nnn
+\end{verbatim}
+\normalsize
+
+where {\bf nnn} must be the same for both records and must be identical to the
+driver's fixed block size.
+
+We recommend that you avoid this configuration if at all possible by using
+variable block sizes.
+
+If you must run with fixed size blocks, make sure they are not 512 bytes. This
+is too small and the overhead that Bacula has with each record will become
+excessive. If at all possible set any fixed block size to something like
+64,512 bytes or possibly 32,768 if 64,512 is too large for your drive. See
+below for the details on checking and setting the default drive block size.
+
+To recover files from tapes written in fixed block mode, see below.
+
+\label{TapeModes}
+\subsection{Ensuring that the Tape Modes Are Properly Set -- {\bf Linux
+Only}}
+\index[general]{Ensuring that the Tape Modes Are Properly Set -- Linux Only}
+
+If you have a modern SCSI tape drive and you are having problems with the {\bf
+test} command as noted above, it may be that some program has set one or more
+of your SCSI driver's options to non-default values. For example, if your
+driver is set to work in SysV manner, Bacula will not work correctly because
+it expects BSD behavior. To reset your tape drive to the default values, you
+can try the following, but {\bf ONLY} if you have a SCSI tape drive on a {\bf
+Linux} system:
+
+\footnotesize
+\begin{verbatim}
+become super user
+mt -f /dev/nst0 rewind
+mt -f /dev/nst0 stoptions buffer-writes async-writes read-ahead
+\end{verbatim}
+\normalsize
+
+The above commands will clear all options and then set those specified. None
+of the specified options are required by Bacula, but a number of other options
+such as SysV behavior must not be set. Bacula does not support SysV tape
+behavior. On systems other than Linux, you will need to consult your {\bf mt}
+man pages or documentation to figure out how to do the same thing. This should
+not really be necessary though -- for example, on both Linux and Solaris
+systems, the default tape driver options are compatible with Bacula.
+On Solaris systems, you must take care to specify the correct device
+name on the {\bf Archive device} directive. See above for more details.
+
+You may also want to ensure that no prior program has set the default block
+size, as happened to one user, by explicitly turning it off with:
+
+\footnotesize
+\begin{verbatim}
+mt -f /dev/nst0 defblksize 0
+\end{verbatim}
+\normalsize
+
+If you are running a Linux
+system, and the above command does not work, it is most likely because you
+have not loaded the appropriate {\bf mt} package, which is often called
+{\bf mt\_st}, but may differ according to your distribution.
+
+If you would like to know what options you have set before making any of the
+changes noted above, you can now view them on Linux systems, thanks to a tip
+provided by Willem Riede. Do the following:
+
+\footnotesize
+\begin{verbatim}
+become super user
+mt -f /dev/nst0 stsetoptions 0
+grep st0 /var/log/messages
+\end{verbatim}
+\normalsize
+
+and you will get output that looks something like the following:
+
+\footnotesize
+\begin{verbatim}
+kernel: st0: Mode 0 options: buffer writes: 1, async writes: 1, read ahead: 1
+kernel: st0: can bsr: 0, two FMs: 0, fast mteom: 0, auto lock: 0,
+kernel: st0: defs for wr: 0, no block limits: 0, partitions: 0, s2 log: 0
+kernel: st0: sysv: 0 nowait: 0
+\end{verbatim}
+\normalsize
+
+Note, I have chopped off the beginning of the line with the date and machine
+name for presentation purposes.
+
+Some people find that the above settings only last until the next reboot, so
+please check this otherwise you may have unexpected problems.
+
+Beginning with Bacula version 1.35.8, if Bacula detects that you are running
+in variable block mode, it will attempt to set your drive appropriately. All
+OSes permit setting variable block mode, but some OSes do not permit setting
+the other modes that Bacula needs to function properly.
+
+\label{compression}
+\subsection{Tape Hardware Compression and Blocking Size}
+\index[general]{Tape Hardware Compression and Blocking Size}
+\index[general]{Size!Tape Hardware Compression and Blocking Size}
+
+You should be able to verify the tape compression status with sysfs on Linux.
+\begin{verbatim}
+cat /sys/class/scsi_tape/nst0/default_compression
+\end{verbatim}
+
+You can, turn it on by using (on Linux):
+
+\footnotesize
+\begin{verbatim}
+become super user
+mt -f /dev/nst0 defcompression 1
+\end{verbatim}
+\normalsize
+
+and of course, if you use a zero instead of the one at the end, you will turn
+it off.
+
+If you have built the {\bf mtx} program in the {\bf depkgs} package, you can
+use tapeinfo to get quite a bit of information about your tape drive even if
+it is not an autochanger. This program is called using the SCSI control
+device. On Linux for tape drive /dev/nst0, this is usually /dev/sg0, while on
+FreeBSD for /dev/nsa0, the control device is often /dev/pass2. For example on
+my DDS-4 drive (/dev/nst0), I get the following:
+
+\footnotesize
+\begin{verbatim}
+tapeinfo -f /dev/sg0
+Product Type: Tape Drive
+Vendor ID: 'HP '
+Product ID: 'C5713A '
+Revision: 'H107'
+Attached Changer: No
+MinBlock:1
+MaxBlock:16777215
+SCSI ID: 5
+SCSI LUN: 0
+Ready: yes
+BufferedMode: yes
+Medium Type: Not Loaded
+Density Code: 0x26
+BlockSize: 0
+\end{verbatim}
+\normalsize
+
+where the {\bf DataCompEnabled: yes} means that tape hardware compression is
+turned on. You can turn it on and off (yes|no) by using the {\bf mt}
+commands given above. Also, this output will tell you if the {\bf BlockSize}
+is non-zero and hence set for a particular block size. Bacula is not likely to
+work in such a situation because it will normally attempt to write blocks of
+64,512 bytes, except the last block of the job which will generally be
+shorter. The first thing to try is setting the default block size to zero
+using the {\bf mt -f /dev/nst0 defblksize 0} command as shown above.
+On FreeBSD, this would be something like: {\bf mt -f /dev/nsa0 blocksize 0}.
+
+On some operating systems with some tape drives, the amount of data that
+can be written to the tape and whether or not compression is enabled is
+determined by the density usually the {\bf mt -f /dev/nst0 setdensity xxx} command.
+Often {\bf mt -f /dev/nst0 status} will print out the current
+density code that is used with the drive. Most systems, but unfortunately
+not all, set the density to the maximum by default. On some systems, you
+can also get a list of all available density codes with:
+{\bf mt -f /dev/nst0 densities} or a similar {\bf mt} command.
+Note, for DLT and SDLT devices, no-compression versus compression is very
+often controlled by the density code. On FreeBSD systems, the compression
+mode is set using {\bf mt -f /dev/nsa0 comp xxx} where xxx is the
+mode you want. In general, see {\bf man mt} for the options available on
+your system.
+
+Note, some of the above {\bf mt} commands may not be persistent depending
+on your system configuration. That is they may be reset if a program
+other than Bacula uses the drive or, as is frequently the case, on reboot
+of your system.
+
+If your tape drive requires fixed block sizes (very unusual), you can use the
+following records:
+
+\footnotesize
+\begin{verbatim}
+Minimum Block Size = nnn
+Maximum Block Size = nnn
+\end{verbatim}
+\normalsize
+
+in your Storage daemon's Device resource to force Bacula to write fixed size
+blocks (where you sent nnn to be the same for both of the above records). This
+should be done only if your drive does not support variable block sizes, or
+you have some other strong reasons for using fixed block sizes. As mentioned
+above, a small fixed block size of 512 or 1024 bytes will be very inefficient.
+Try to set any fixed block size to something like 64,512 bytes or larger if
+your drive will support it.
+
+Also, note that the {\bf Medium Type} field of the output of {\bf tapeinfo}
+reports {\bf Not Loaded}, which is not correct. As a consequence, you should
+ignore that field as well as the {\bf Attached Changer} field.
+
+To recover files from tapes written in fixed block mode, see below.
+\label{FreeBSDTapes}
+
+\subsection{Tape Modes on FreeBSD}
+\index[general]{FreeBSD!Tape Modes on}
+\index[general]{Tape Modes on FreeBSD}
+
+On most FreeBSD systems such as 4.9 and most tape drives, Bacula should run
+with:
+
+\footnotesize
+\begin{verbatim}
+mt -f /dev/nsa0 seteotmodel 2
+mt -f /dev/nsa0 blocksize 0
+mt -f /dev/nsa0 comp enable
+\end{verbatim}
+\normalsize
+
+You might want to put those commands in a startup script to make sure your
+tape driver is properly initialized before running Bacula, because
+depending on your system configuration, these modes may be reset if a
+program other than Bacula uses the drive or when your system is rebooted.
+
+Then according to what the {\bf btape test} command returns, you will probably
+need to set the following (see below for an alternative):
+
+\footnotesize
+\begin{verbatim}
+ Hardware End of Medium = no
+ BSF at EOM = yes
+ Backward Space Record = no
+ Backward Space File = no
+ Fast Forward Space File = no
+ TWO EOF = yes
+\end{verbatim}
+\normalsize
+
+Then be sure to run some append tests with Bacula where you start and stop
+Bacula between appending to the tape, or use {\bf btape} version 1.35.1 or
+greater, which includes simulation of stopping/restarting Bacula.
+
+Please see the file {\bf platforms/freebsd/pthreads-fix.txt} in the main
+Bacula directory concerning {\bf important} information concerning
+compatibility of Bacula and your system. A much more optimal Device
+configuration is shown below, but does not work with all tape drives. Please
+test carefully before putting either into production.
+
+Note, for FreeBSD 4.10-RELEASE, using a Sony TSL11000 L100 DDS4 with an
+autochanger set to variable block size and DCLZ compression, Brian McDonald
+reports that to get Bacula to append correctly between Bacula executions,
+the correct values to use are:
+
+\footnotesize
+\begin{verbatim}
+mt -f /dev/nsa0 seteotmodel 1
+mt -f /dev/nsa0 blocksize 0
+mt -f /dev/nsa0 comp enable
+\end{verbatim}
+\normalsize
+
+and
+
+\footnotesize
+\begin{verbatim}
+ Hardware End of Medium = no
+ BSF at EOM = no
+ Backward Space Record = no
+ Backward Space File = no
+ Fast Forward Space File = yes
+ TWO EOF = no
+\end{verbatim}
+\normalsize
+
+This has been confirmed by several other people using different hardware. This
+configuration is the preferred one because it uses one EOF and no backspacing
+at the end of the tape, which works much more efficiently and reliably with
+modern tape drives.
+
+Finally, here is a Device configuration that Danny Butroyd reports to work
+correctly with the Overland Powerloader tape library using LT0-2 and
+FreeBSD 5.4-Stable:
+
+\footnotesize
+\begin{verbatim}
+# Overland Powerloader LT02 - 17 slots single drive
+Device {
+ Name = Powerloader
+ Media Type = LT0-2
+ Archive Device = /dev/nsa0
+ AutomaticMount = yes;
+ AlwaysOpen = yes;
+ RemovableMedia = yes;
+ RandomAccess = no;
+ Changer Command = "/usr/local/sbin/mtx-changer %c %o %S %a %d"
+ Changer Device = /dev/pass2
+ AutoChanger = yes
+ Alert Command = "sh -c 'tapeinfo -f %c |grep TapeAlert|cat'"
+
+ # FreeBSD Specific Settings
+ Offline On Unmount = no
+ Hardware End of Medium = no
+ BSF at EOM = yes
+ Backward Space Record = no
+ Fast Forward Space File = no
+ TWO EOF = yes
+}
+
+The following Device resource works fine with Dell PowerVault 110T and
+120T devices on both FreeBSD 5.3 and on NetBSD 3.0. It also works
+with Sony AIT-2 drives on FreeBSD.
+\footnotesize
+\begin{verbatim}
+Device {
+ ...
+ # FreeBSD/NetBSD Specific Settings
+ Hardware End of Medium = no
+ BSF at EOM = yes
+ Backward Space Record = no
+ Fast Forward Space File = yes
+ TWO EOF = yes
+}
+\end{verbatim}
+\normalsize
+
+On FreeBSD version 6.0, it is reported that you can even set
+Backward Space Record = yes.
+
+
+
+\subsection{Finding your Tape Drives and Autochangers on FreeBSD}
+\index[general]{FreeBSD!Finding Tape Drives and Autochangers}
+\index[general]{Finding Tape Drives and Autochangers on FreeBSD}
+
+On FreeBSD, you can do a {\bf camcontrol devlist} as root to determine what
+drives and autochangers you have. For example,
+
+\footnotesize
+\begin{verbatim}
+undef# camcontrol devlist
+ at scbus0 target 2 lun 0 (pass0,sa0)
+ at scbus0 target 4 lun 0 (pass1,sa1)
+ at scbus0 target 4 lun 1 (pass2)
+\end{verbatim}
+\normalsize
+
+from the above, you can determine that there is a tape drive on {\bf /dev/sa0}
+and another on {\bf /dev/sa1} in addition since there is a second line for the
+drive on {\bf /dev/sa1}, you know can assume that it is the control device for
+the autochanger (i.e. {\bf /dev/pass2}). It is also the control device name to
+use when invoking the tapeinfo program. E.g.
+
+\footnotesize
+\begin{verbatim}
+tapeinfo -f /dev/pass2
+\end{verbatim}
+\normalsize
+
+\label{onstream}
+
+\subsection{Using the OnStream driver on Linux Systems}
+\index[general]{Using the OnStream driver on Linux Systems}
+\index[general]{Systems!Using the OnStream driver on Linux}
+
+Bacula version 1.33 (not 1.32x) is now working and ready for testing with the
+OnStream kernel osst driver version 0.9.14 or above. Osst is available from:
+\elink{http://sourceforge.net/projects/osst/}
+{http://sourceforge.net/projects/osst/}.
+
+To make Bacula work you must first load the new driver then, as root, do:
+
+\footnotesize
+\begin{verbatim}
+ mt -f /dev/nosst0 defblksize 32768
+\end{verbatim}
+\normalsize
+
+Also you must add the following to your Device resource in your Storage
+daemon's conf file:
+
+\footnotesize
+\begin{verbatim}
+ Minimum Block Size = 32768
+ Maximum Block Size = 32768
+\end{verbatim}
+\normalsize
+
+Here is a Device specification provided by Michel Meyers that is known to
+work:
+
+\footnotesize
+\begin{verbatim}
+Device {
+ Name = "Onstream DI-30"
+ Media Type = "ADR-30"
+ Archive Device = /dev/nosst0
+ Minimum Block Size = 32768
+ Maximum Block Size = 32768
+ Hardware End of Medium = yes
+ BSF at EOM = no
+ Backward Space File = yes
+ Fast Forward Space File = yes
+ Two EOF = no
+ AutomaticMount = yes
+ AlwaysOpen = yes
+ Removable Media = yes
+}
+\end{verbatim}
+\normalsize
+
+\section{Hardware Compression on EXB-8900}
+\index[general]{Hardware Compression on EXB-8900}
+\index[general]{EXB-8900!Hardware Compression}
+
+To active, check, or disable the hardware compression feature
+on an EXB-8900, use the exabyte MammothTool. You can get it here:
+\elink{http://www.exabyte.com/support/online/downloads/index.cfm}
+{http://www.exabyte.com/support/online/downloads/index.cfm}.
+There is a Solaris version of this tool. With option -C 0 or 1 you
+can disable or activate compression. Start this tool without any
+options for a small reference.
+
+\label{fill}
+\subsection{Using btape to Simulate Filling a Tape}
+\index[general]{Using btape to Simulate Filling a Tape}
+\index[general]{Tape!Using btape to Simulate Filling}
+
+Because there are often problems with certain tape drives or systems when end
+of tape conditions occur, {\bf btape} has a special command {\bf fill} that
+causes it to write random data to a tape until the tape fills. It then writes
+at least one more Bacula block to a second tape. Finally, it reads back both
+tapes to ensure that the data has been written in a way that Bacula can
+recover it. Note, there is also a single tape option as noted below, which you
+should use rather than the two tape test. See below for more details.
+
+This can be an extremely time consuming process (here it is about 6 hours) to
+fill a full tape. Note, that btape writes random data to the tape when it is
+filling it. This has two consequences: 1. it takes a bit longer to generate
+the data, especially on slow CPUs. 2. the total amount of data is
+approximately the real physical capacity of your tape, regardless of whether
+or not the tape drive compression is on or off. This is because random data
+does not compress very much.
+
+To begin this test, you enter the {\bf fill} command and follow the
+instructions. There are two options: the simple single tape option and the
+multiple tape option. Please use only the simple single tape option because
+the multiple tape option still doesn't work totally correctly. If the single
+tape option does not succeed, you should correct the problem before using
+Bacula.
+\label{RecoveringFiles}
+
+\section{Recovering Files Written With Fixed Block Sizes}
+\index[general]{Recovering Files Written With Fixed Block Sizes}
+
+If you have been previously running your tape drive in fixed block mode
+(default 512) and Bacula with variable blocks (default), then in version
+1.32f-x and 1.34 and above, Bacula will fail to recover files because it does
+block spacing, and because the block sizes don't agree between your tape drive
+and Bacula it will not work.
+
+The long term solution is to run your drive in variable block mode as
+described above. However, if you have written tapes using fixed block sizes,
+this can be a bit of a pain. The solution to the problem is: while you are
+doing a restore command using a tape written in fixed block size, ensure that
+your drive is set to the fixed block size used while the tape was written.
+Then when doing the {\bf restore} command in the Console program, do not
+answer the prompt {\bf yes/mod/no}. Instead, edit the bootstrap file (the
+location is listed in the prompt) using any ASCII editor. Remove all {\bf
+VolBlock} lines in the file. When the file is re-written, answer the question,
+and Bacula will run without using block positioning, and it should recover
+your files.
+
+\label{BlockModes}
+\section{Tape Blocking Modes}
+\index[general]{Modes!Tape Blocking}
+\index[general]{Tape Blocking Modes}
+
+SCSI tapes may either be written in {\bf variable} or {\bf fixed} block sizes.
+Newer drives support both modes, but some drives such as the QIC devices
+always use fixed block sizes. Bacula attempts to fill and write complete
+blocks (default 65K), so that in normal mode (variable block size), Bacula
+will always write blocks of the same size except the last block of a Job. If
+Bacula is configured to write fixed block sizes, it will pad the last block of
+the Job to the correct size. Bacula expects variable tape block size drives to
+behave as follows: Each write to the drive results in a single record being
+written to the tape. Each read returns a single record. If you request less
+bytes than are in the record, only those number of bytes will be returned, but
+the entire logical record will have been read (the next read will retrieve the
+next record). Thus data from a single write is always returned in a single
+read, and sequentially written records are returned by sequential reads.
+
+Bacula expects fixed block size tape drives to behave as follows: If a write
+length is greater than the physical block size of the drive, the write will be
+written as two blocks each of the fixed physical size. This single write may
+become multiple physical records on the tape. (This is not a good situation).
+According to the documentation, one may never write an amount of data that is
+not the exact multiple of the blocksize (it is not specified if an error
+occurs or if the the last record is padded). When reading, it is my
+understanding that each read request reads one physical record from the tape.
+Due to the complications of fixed block size tape drives, you should avoid
+them if possible with Bacula, or you must be ABSOLUTELY certain that you use
+fixed block sizes within Bacula that correspond to the physical block size of
+the tape drive. This will ensure that Bacula has a one to one correspondence
+between what it writes and the physical record on the tape.
+
+Please note that Bacula will not function correctly if it writes a block and
+that block is split into two or more physical records on the tape. Bacula
+assumes that each write causes a single record to be written, and that it can
+sequentially recover each of the blocks it has written by using the same
+number of sequential reads as it had written.
+
+\section{Details of Tape Modes}
+\index[general]{Modes!Details}
+\index[general]{Details of Tape Modes}
+Rudolf Cejka has provided the following information concerning
+certain tape modes and MTEOM.
+
+\begin{description}
+\item[Tape level]
+ It is always possible to position filemarks or blocks, whereas
+ positioning to the end-of-data is only optional feature, however it is
+ implemented very often. SCSI specification also talks about optional
+ sequential filemarks, setmarks and sequential setmarks, but these are not
+ implemented so often. Modern tape drives keep track of file positions in
+ built-in chip (AIT, LTO) or at the beginning of the tape (SDLT), so there
+ is not any speed difference, if end-of-data or filemarks is used (I have
+ heard, that LTO-1 from all 3 manufacturers do not use its chip for file
+ locations, but a tape as in SDLT case, and I'm not sure about LTO-2 and
+ LTO-3 case). However there is a big difference, that end-of-data ignores
+ file position, whereas filemarks returns the real number of skipped
+ files, so OS can track current file number just in filemarks case.
+
+\item[OS level]
+ Solaris does use just SCSI SPACE Filemarks, it does not support SCSI
+ SPACE End-of-data. When MTEOM is called, Solaris does use SCSI SPACE
+ Filemarks with count = 1048576 for fast mode, and combination of SCSI
+ SPACE Filemarks with count = 1 with SCSI SPACE Blocks with count = 1 for
+ slow mode, so EOD mark on the tape on some older tape drives is not
+ skipped. File number is always tracked for MTEOM.
+
+ Linux does support both SCSI SPACE Filemarks and End-of-data: When MTEOM
+ is called in MT\_ST\_FAST\_MTEOM mode, SCSI SPACE End-of-data is used.
+ In the other case, SCSI SPACE Filemarks with count =
+ 8388607 is used.
+ There is no real slow mode like in Solaris - I just expect, that for
+ older tape drives Filemarks may be slower than End-of-data, but not so
+ much as in Solaris slow mode. File number is tracked for MTEOM just
+ without MT\_ST\_FAST\_MTEOM - when MT\_ST\_FAST\_MTEOM is used, it is not.
+
+ FreeBSD does support both SCSI SPACE Filemarks and End-of-data, but when
+ MTEOD (MTEOM) is called, SCSI SPACE End-of-data is always used. FreeBSD
+ never use SCSI SPACE Filemarks for MTEOD. File number is never tracked
+ for MTEOD.
+
+\item[Bacula level]
+ When {\bf Hardware End of Medium = Yes} is used, MTEOM is called, but it
+ does not mean, that hardware End-of-data must be used. When Hardware End
+ of Medium = No, if Fast Forward Space File = Yes, MTFSF with count =
+ 32767 is used, else Block Read with count = 1 with Forward Space File
+ with count = 1 is used, which is really very slow.
+
+\item [Hardware End of Medium = Yes|No]
+ The name of this option is misleading and is the source of confusion,
+ because it is not the hardware EOM, what is really switched here.
+
+ If I use Yes, OS must not use SCSI SPACE End-of-data, because Bacula
+ expects, that there is tracked file number, which is not supported by
+ SCSI specification. Instead, the OS have to use SCSI SPACE Filemarks.
+
+ If I use No, an action depends on Fast Forward Space File.
+
+ When I set {\bf Hardware End of Medium = no}
+ and {\bf Fast Forward Space File = no}
+ file positioning was very slow
+ on my LTO-3 (about ten to 100 minutes), but
+
+ with {\bf Hardware End of Medium = no} and
+{\bf Fast Forward Space File = yes}, the time is ten to
+100 times faster (about one to two minutes).
+
+\end{description}
+
+\section{Tape Performance Problems}
+\index[general]{Tape Performance}
+If you have LTO-3 or LTO-4 drives, you should be able to
+fairly good transfer rates; from 60 to 150 MB/second, providing
+you have fast disks; GigaBit Ethernet connections (probably 2); you are
+running multiple simultaneous jobs; you have Bacula data spooling
+enabled; your tape block size is set to 131072 or 262144; and
+you have set {\bf Maximum File Size = 5G}.
+
+If you are not getting good performance, consider some of the following
+suggestions from the Allen Balck on the Bacula Users email list:
+
+\begin{enumerate}
+\item You are using an old HBA (i.e. SCSI-1, which only does 5 MB/s)
+
+\item There are other, slower, devices on the SCSI bus. The HBA will
+ negotiate the speed of every device down to the speed of the
+ slowest.
+
+\item There is a termination problem on the bus (either too much or
+ too little termination). The HBA will drop the bus speed in an
+ attempt to increase the reliability of the bus.
+
+\item Loose or damaged cabling - this will probably make the HBA "think"
+ you have a termination problem and it will react as in 3 above.
+\end{enumerate}
+
+See if /var/adm/messages (or /var/log/messages) tells you what the sync
+rate of the SCSI devices/bus are. Also, the next time you reboot, the
+BIOS may be able to tell you what the rate of each device is.
+
+
+\section{Autochanger Errors}
+\index[general]{Errors!Autochanger}
+\index[general]{Autochanger Errors}
+
+If you are getting errors such as:
+
+\footnotesize
+\begin{verbatim}
+3992 Bad autochanger "load slot 1, drive 1": ERR=Child exited with code 1.
+\end{verbatim}
+\normalsize
+
+and you are running your Storage daemon as non-root, then most likely
+you are having permissions problems with the control channel. Running
+as root, set permissions on /dev/sgX so that the userid and group of
+your Storage daemon can access the device. You need to ensure that you
+all access to the proper control device, and if you don't have any
+SCSI disk drives (including SATA drives), you might want to change
+the permissions on /dev/sg*.
+
+\section{Syslog Errors}
+\index[general]{Errors!Syslog}
+\index[general]{Syslog Errors}
+
+If you are getting errors such as:
+
+\footnotesize
+\begin{verbatim}
+: kernel: st0: MTSETDRVBUFFER only allowed for root
+\end{verbatim}
+\normalsize
+
+you are most likely running your Storage daemon as non-root, and
+Bacula is attempting to set the correct OS buffering to correspond
+to your Device resource. Most OSes allow only root to issue this
+ioctl command. In general, the message can be ignored providing
+you are sure that your OS parameters are properly configured as
+described earlier in this manual. If you are running your Storage daemon
+as root, you should not be getting these system log messages, and if
+you are, something is probably wrong.
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