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