\begin{itemize}
\item A script that actually controls the autochanger according to commands
sent by Bacula. We furnish such a script that works with {\bf mtx} found in
- the {\bf depkgs} distribution. This script works only with single drive
- autochangers.
+ the {\bf depkgs} distribution.
\item That each Volume (tape) to be used must be defined in the Catalog and
have a Slot number assigned to it so that Bacula knows where the Volume is in
- the autochanger. This is generally done with the {\bf label} command. See
+ the autochanger. This is generally done with the {\bf label} command,
+ but can also done after the tape is labeled using the {\bf update slots}
+ command. See
below for more details. You must pre-label the tapes manually before
- using them.
+ using them.
\item Modifications to your Storage daemon's Device configuration resource to
identify that the device is a changer, as well as a few other parameters.
In version 1.37 and later, there is a new \ilink{Autochanger
resource}{AutochangerRes} that permits you to group Device resources thus
creating a multi-drive autochanger. If you have an autochanger,
-you must use this new resource.
+you {\bf must} use this new resource.
Bacula uses its own {\bf mtx-changer} script to interface with a program
that actually does the tape changing. Thus in principle, {\bf mtx-changer}
Support" section below.
Current Bacula autochanger support does not include cleaning, stackers, or
-silos. However, under certain conditions, you may be able to make Bacula
-work with stackers (gravity feed and such). Support for multi-drive
+silos. Stackers and silos are not supported because Bacula expects to
+be able to access the Slots randomly.
+However, if you are very careful to setup Bacula to access the Volumes
+in the autochanger sequentially, you may be able to make Bacula
+work with stackers (gravity feed and such).
+
+Support for multi-drive
autochangers requires the \ilink{Autochanger resource}{AutochangerRes}
introduced in version 1.37. This resource is also recommended for single
drive autochangers.
The home page for the {\bf mtx} project can be found at:
\elink{http://mtx.opensource-sw.net/}{http://mtx.opensource-sw.net/}.
+Note, we have feedback from some users that there are certain
+incompatibilities between the Linux kernel and mtx. For example between
+kernel 2.6.18-8.1.8.el5 of CentOS and RedHat and version 1.3.10 and 1.3.11
+of mtx. This was fixed by upgrading to a version 2.6.22 kernel.
+
+In addition, apparently certain versions of mtx, for example, version
+1.3.11 limit the number of slots to a maximum of 64. The solution was to
+use version 1.3.10.
+
If you are having troubles, please use the {\bf auto} command in the {\bf
btape} program to test the functioning of your autochanger with Bacula. When
Bacula is running, please remember that for many distributions (e.g. FreeBSD,
root.root}, so you will need to ensure that the Storage daemon has sufficient
permissions to access the autochanger.
+Some users have reported that the the Storage daemon blocks under certain
+circumstances in trying to mount a volume on a drive that has a different
+volume loaded. As best we can determine, this is simply a matter of
+waiting a bit. The drive was previously in use writing a Volume, and
+sometimes the drive will remain BLOCKED for a good deal of time (up to 7
+minutes on a slow drive) waiting for the cassette to rewind and to unload
+before the drive can be used with a different Volume.
+
\label{SCSI devices}
\section{Knowing What SCSI Devices You Have}
\index[general]{Have!Knowing What SCSI Devices You }
Bacula will not automatically use a Volume in your autochanger unless it is
labeled and the slot number is stored in the catalog and the Volume is marked
-as InChanger. For each Volume in your
+as InChanger. This is because it must know where each volume is (slot) to
+be able to load the volume.
+For each Volume in your
changer, you will, using the Console program, assign a slot. This information
is kept in {\bf Bacula's} catalog database along with the other data for the
volume. If no slot is given, or the slot is set to zero, Bacula will not
attempt to use the autochanger even if all the necessary configuration records
-are present. In addition, the console {\bf mount} command does not cause
-Bacula to operate the autochanger, it only tells Bacula to read any tape that
-may be in the drive.
+are present. When doing a {\bf mount} command on an autochanger, you must
+specify which slot you want mounted. If the drive is loaded with a tape
+from another slot, it will unload it and load the correct tape, but
+normally, no tape will be loaded because an {\bf unmount} command causes
+Bacula to unload the tape in the drive.
+
You can check if the Slot number and InChanger flag are set by doing a:
\begin{verbatim}
the number should be terminated by a colon ({\bf :}). If your changer has
barcodes, the barcode will follow the colon. If an error message is printed,
you must resolve the problem (e.g. try a different SCSI control device name
-if {\bf /dev/sg0} is incorrect. For example, on FreeBSD systems, the
+if {\bf /dev/sg0} is incorrect). For example, on FreeBSD systems, the
autochanger SCSI control device is generally {\bf /dev/pass2}.
\item [/etc/bacula/mtx-changer \ /dev/sg0 \ slots ]
\index[general]{Bacula Autochanger Interface }
Bacula calls the autochanger script that you specify on the {\bf Changer
-Device} statement. Normally this script will be the {\bf mtx-changer} script
-that we can provide, but it can in fact be any program. The only requirements
-are that the "commands" that Bacula uses are {\bf loaded}, {\bf load}, {\bf
+Command} statement. Normally this script will be the {\bf mtx-changer} script
+that we provide, but it can in fact be any program. The only requirement
+for the script is that it must understand the commands that
+Bacula uses, which are {\bf loaded}, {\bf load}, {\bf
unload}, {\bf list}, and {\bf slots}. In addition,
each of those commands must return the information in the precise format as
specified below:
\normalsize
Bacula checks the exit status of the program called, and if it is zero, the
-data is accepted. If the exit status is non-zero, Bacula ignores any
-information returned and treats the drive as if it is not an autochanger.
+data is accepted. If the exit status is non-zero, Bacula will print an
+error message and request the tape be manually mounted on the drive.
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