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\chapter{Data Spooling}
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\label{SpoolingChapter}
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\index[general]{Data Spooling }
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\index[general]{Spooling!Data }
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Bacula allows you to specify that you want the Storage daemon to initially
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write your data to disk and then subsequently to tape. This serves several
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\item It takes a long time for data to come in from the File daemon during
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an Incremental backup. If it is directly written to tape, the tape will
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start and stop or shoe-shine as it is often called causing tape wear.
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By first writing the data to disk, then writing it to tape, the tape can
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be kept in continual motion.
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\item While the spooled data is being written to the tape, the despooling
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process has exclusive use of the tape. This means that you can spool
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multiple simultaneous jobs to disk, then have them very efficiently
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despooled one at a time without having the data blocks from several jobs
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intermingled, thus substantially improving the time needed to restore
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files. While despooling, all jobs spooling continue running.
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\item Writing to a tape can be slow. By first spooling your data to disk,
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you can often reduce the time the File daemon is running on a system,
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thus reducing downtime, and/or interference with users. Of course, if
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your spool device is not large enough to hold all the data from your
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File daemon, you may actually slow down the overall backup.
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Data spooling is exactly that "spooling". It is not a way to first write a
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"backup" to a disk file and then to a tape. When the backup has only been
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spooled to disk, it is not complete yet and cannot be restored until it is
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Bacula version 1.39.x and later supports writing a backup
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to disk then later {\bf Migrating} or moving it to a tape (or any
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details on this, please see the \ilink{Migration}{MigrationChapter} chapter
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of this manual for more details.
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The remainder of this chapter explains the various directives that you can use
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in the spooling process.
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\section{Data Spooling Directives}
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\index[general]{Directives!Data Spooling }
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\index[general]{Data Spooling Directives }
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The following directives can be used to control data spooling.
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\item To turn data spooling on/off at the Job level in the Job resource in
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the Director's conf file (default {\bf no}).
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{\bf SpoolData = yes\vb{}no}
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\item To override the Job specification in a Schedule Run directive in the
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{\bf SpoolData = yes\vb{}no}
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\item To override the Job specification in a bconsole session using the \texttt{run}
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command. Please note that this does {\bf not } refer to a configuration
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statement, but to an argument for the run command.
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{\bf SpoolData=yes\vb{}no}
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\item To limit the the maximum spool file size for a particular job in the Job
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{\bf Spool Size = size}
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Where size is a the maximum spool size for this job specified in bytes.
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\item To limit the maximum total size of the spooled data for a particular
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device. Specified in the Device resource of the Storage daemon's conf file
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{\bf Maximum Spool Size = size}
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Where size is a the maximum spool size for all jobs specified in bytes.
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\item To limit the maximum total size of the spooled data for a particular
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device for a single job. Specified in the Device Resource of the Storage
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daemon's conf file (default unlimited).
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{\bf Maximum Job Spool Size = size}
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Where size is the maximum spool file size for a single job specified in
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\item To specify the spool directory for a particular device. Specified in
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the Device Resource of the Storage daemon's conf file (default, the working
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{\bf Spool Directory = directory}
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% TODO: fix this section name
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\section{!!! MAJOR WARNING !!!}
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\index[general]{WARNING! MAJOR }
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\index[general]{ MAJOR WARNING }
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Please be very careful to exclude the spool directory from any backup,
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otherwise, your job will write enormous amounts of data to the Volume, and
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most probably terminate in error. This is because in attempting to backup the
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spool file, the backup data will be written a second time to the spool file,
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and so on ad infinitum.
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Another advice is to always specify the maximum spool size so that your disk
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doesn't completely fill up. In principle, data spooling will properly detect a
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full disk, and despool data allowing the job to continue. However, attribute
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spooling is not so kind to the user. If the disk on which attributes are being
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spooled fills, the job will be canceled. In addition, if your working
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directory is on the same partition as the spool directory, then Bacula jobs
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will fail possibly in bizarre ways when the spool fills.
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\section{Other Points}
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\index[general]{Points!Other }
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\index[general]{Other Points }
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\item When data spooling is enabled, Bacula automatically turns on attribute
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spooling. In other words, it also spools the catalog entries to disk. This is
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done so that in case the job fails, there will be no catalog entries
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pointing to non-existent tape backups.
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\item Attribute despooling occurs near the end of a job. The Storage daemon
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accumulates file attributes during the backup and sends them to the
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Director at the end of the job. The Director then inserts the file
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attributes into the catalog. During this insertion, the tape drive may
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be inactive. When the file attribute insertion is completed, the job
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\item Attribute spool files are always placed in the working directory of
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\item When Bacula begins despooling data spooled to disk, it takes exclusive
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use of the tape. This has the major advantage that in running multiple
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simultaneous jobs at the same time, the blocks of several jobs will not be
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\item It probably does not make a lot of sense to enable data spooling if you
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are writing to disk files.
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\item It is probably best to provide as large a spool file as possible to
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avoid repeatedly spooling/despooling. Also, while a job is despooling to
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tape, the File daemon must wait (i.e. spooling stops for the job while it is
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\item If you are running multiple simultaneous jobs, Bacula will continue
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spooling other jobs while one is despooling to tape, provided there is
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sufficient spool file space.
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