
#include "bacula_template.inc" title="Recycling Volumes" num=11

<h1>Automatic Volume Recycling</h1>
Normally, Bacula will write on a volume, and once the
tape is written, it can append to the volume, but it will 
never overwrite the data thus destroying it. When we
speak of <b>recycling</b> volumes, we mean that <b>Bacula</b>
can write over the previous contents of a volume. Thus all
previous data will be lost.   
<p>
If you are like me, you may not want Bacula to automatically
recycle (reuse) tapes. This requires a large number of tapes, and
when I need  a tape, I manually recycle it. For more on 
manual recycling, see the section entitled 
<a href="recycling.html#manualrecycling">
Manually Recycling Volumes</a> below in this chapter.
<p>
Most people prefer to have a Pool
of tapes that are used for daily backups and recycled once a week,
another Pool of tapes that are used for Full backups once a week
and recycled monthly, and finally a Pool of tapes that are used
once a month and recycled after a year or two. With a scheme
like this, your pool of tapes remains constant.      
<p>By properly defining your Volume Pools with appropriate Retention
periods, Bacula can manage the recycling (such as defined 
above) automatically.
<p>Automatic recycling of Volumes is controlled by three
records in the <b>Pool</b> resource definition in the Director's
configuration file. These three records are:
<b>
<ul type="disc">
<li>AutoPrune = yes</li>
<li>VolumeRetention = &lt;time&gt;</li>
<li>Recycle = yes</li>
</ul>
</b>
Automatic recycling of Volumes is performed by Bacula only when
it wants a new Volume and no appendable Volumes are available in the
Pool. It will then search the Pool for any Volumes with the
<b>Recycle</b> flag set and whose Volume Status is <b>Full</b>.  At that
point, the recycling occurs in two steps.  The first is that a Volume
must be purged of all Jobs and Files, and the second step is the actual
recycling of the Volume. The Volume will be purged if the VolumeRetention
period has expired.  If no volumes can be recycled for any of the reasons
stated above, Bacula will request operator intervention (i.e.
it will ask you to label a new volume).
<p>
A key point mentioned above that can be a source of frustration is that
Bacula will only recycle purged Volumes if there is no other appendable
Volume available. So, if you wish to &quot;force&quot; Bacula to use
a purged Volume, you must first ensure that no other Volume in the
Pool is marked <b>Append</b>.  If necessary, you can manually set a volume
to <b>Full</b>.  The reason for this is that Bacula wants to preserve the
data on your old tapes (even though purged from the catalog) as long
as absolutely possible before overwriting it.

<a name="AutoPruning">
<h2>Automatic Pruning</h2></a>
There are three pruning durations.  All apply to catalog database
records and not to the actual data in a Volume.As you note, the
pruning (or retention) durations are for: Volumes (Media records),
Jobs (Job records), andFiles (File records).  They are they
inter-depend a bitin the sense that if Bacula prunes a Volume, it
automatically removes all the Job records, and all the File
records,and if a Job record is pruned, all the File records
for that Job are also pruned (deleted).
<p>
Having the File records in the database means that
you can examine all the files backed up for a particular
Job. They take the most space in the catalog (probably 90-95% 
of the total). When the File records are pruned,the Job records 
can remain, and you can still examine what
Jobs ran, but not the details of the Files backed up. In
addition, without the File records, you cannot use the Console
restore command to restore the files.
<p>
When a Job record is pruned, the Volume (Media record)
for that Job can still remain in the database, and if you
do a "list volumes", you will see the volume information, but
the Job records (and its File records) will no longer be available.
<p>
In each case, pruning removes information about where older
files are, but it also prevents the catalog from growing to
be too large.  You choose the retention periods in function
of how many files you are backing up and the time periods
you want to keep those records online, and the size of the
database.You can always re-insert the records (with 98% of the original
data) by using "bscan" to scan in a whole Volume or any
part of the volume that you want.
<p>
By setting <b>AutoPrune</b> to <b>yes</b> you will permit <b>Bacula</b>
to automatically prune all Volumes in the Pool when a Job needs   
another Volume. Volume pruning means removing records from the catalog.
It does not shrink the size of the Volume or effect the Volume
data until the Volume gets overwritten.
When a Job requests another volume and
there are no Volumes with Volume Status
<b>Append</b> available, Bacula will begin volume
pruning. This means that all Jobs that
are older than the <b>VolumeRetention</b> period will be pruned from
every Volume that has Volume Status <b>Full</b> or <b>Used</b>
and has Recycle set to <b>yes</b>. Pruning consists of deleting
the corresponding Job, File, and JobMedia records from the
catalog database. No change to the physical data on the Volume
occurs during the pruning process.
When all files are pruned from a Volume (i.e. no records
in the catalog), the Volume will be marked
as <b>Purged</b> implying that no Jobs remain on the volume.
The Pool records that control the pruning are described below.
<dl>
   <dt>AutoPrune = &lt;yes/no&gt;</dt><dd>If AutoPrune is set to
       <b>yes</b> (default), Bacula (version 1.20 or greater) will
       automatically apply the Volume retention period when running a Job
       and it needs a new Volume but no appendable volumes are available.
       At that point, Bacula will prune all Volumes that can be pruned
       (i.e. AutoPrune set) in an attempt to find a usable volume. If
       during the autoprune, all files are pruned from the Volume, it
       will be marked with VolStatus <b>Purged</b>.
       The default is <b>yes</b>.</dd>

   <dt>Volume Retention = &lt;time-period-specification&gt;</dt><dd>The
       Volume Retention record defines the length of time that
       Bacula will guarantee that the Volume is not reused counting
       from the time the last job stored on the Volume terminated.
       <p>
       When this time period expires, and if <b>AutoPrune</b> is set to
       <b>yes</b>, and a new Volume is needed, but no appendable Volume
       is available, Bacula will prune (remove) Job records that
       are older than the specified Volume Retention period. 
       <p>The Volume Retention period takes precedence 
       over any Job Retention period you have specified in the
       Client resource. It should also be noted, that the Volume
       Retention period is obtained by reading the Catalog Database Media
       record rather than the Pool resource record. This means that
       if you change the VolumeRetention in the Pool resource record,
       you must ensure that the corresponding change is made in the
       catalog by using the <b>update pool</b> command. Doing so
       will insure that any new Volumes will be created with the 
       changed Volume Retention period. Any existing Volumes will
       have their own copy of the Volume Retention period that can
       only be changed on a Volume by Volume basis using the
       <b>update volume</b> command.
       <p>When all file catalog entries are removed from the volume, 
       its VolStatus is set to <b>Purged</b>. The files remain physically
       on the Volume until the volume is overwritten.
       <p>Retention periods are specified in seconds,
       minutes, hours, days, weeks, months,
       quarters, or years on the record.  See the 
       <a href="configure.html#Time">Configuration chapter</a> of this
       manual for additional details of time specification.  
       <p>The default is 1 year.  </dd>

   <dt>Recycle = &lt;yes/no&gt;</dt><dd>This statement tells Bacula
       whether or not the particular Volume can be recycled (i.e.
       rewritten). If Recycle is set to <b>no</b>
       (the default), then even if Bacula prunes all the Jobs
       on the volume and it is marked <b>Purged</b>, it will not
       consider the tape for recycling.  If Recycle is set to <b>yes</b>
       and all Jobs have been pruned, the volume status will be set to
       <b>Purged</b> and the volume may then be reused when another
       volume is needed.  If the volume is reused, it is relabeled with
       the same Volume Name, however all previous data will be lost.</dd>
</dl>
Note, it is also possible to &quot;force&quot; pruning of all
Volumes in the Pool associated with a Job by adding <b>Prune Files = yes</b>
to the Job resource. 

<a name="Recycling">
<h2>Recycling Algorithm</h2></a>
After all Volumes of a Pool have been pruned (as mentioned above, this
happens when a Job needs a new Volume and no appendable Volumes are
available), Bacula will look for the oldest Volume that is
Purged (all Jobs and Files expired), and if the <b>Recycle</b> flag
is on (Recycle=yes) for that Volume, Bacula will relabel it
and write new data on it.
<p>
The full recycling algorithm that Bacula uses when it needs a new
Volume is:
<ul>
 <li>Search the Pool for a Volume with VolStatus=Append (if there is
    more than one, the Volume with the oldest date last written is
    chosen. If two have the same date then the one with
    the lowest MediaId is chosen).</li>
 <li>Search the Pool for a Volume with VolStatus=Recycle (if there is
    more than one, the Volume with the oldest date last written is
    chosen. If two have the same date then the one with
    the lowest MediaId is chosen).</li>
 <li>Prune volumes applying Volume retention period (Volumes with VolStatus
    Full, Used, or Append are pruned).</li>
 <li>Search the Pool for a Volume with VolStatus=Purged</li>
 <li>Attempt to create a new Volume if automatic labeling enabled</li>
 <li>Prune the oldest Volume if RecycleOldestVolume=yes (the Volume
     with the oldest LastWritten date and VolStatus equal to 
     Full, Recycle, Purged, Used, or Append is chosen). This
     record ensures that all retention periods are properly
     respected.
 <li>Purge the oldest Volume if PurgeOldestVolume=yes (the Volume
     with the oldest LastWritten date and VolStatus equal to 
     Full, Recycle, Purged, Used, or Append is chosen). We strongly
     recommend against the use of <b>PurgeOldestVolume</b> as it
     can quite easily lead to loss of current backup data.</li>
 <li>Give up and ask operator.</li>
</ul>
The above occurs when Bacula has finished writing a Volume or 
when no Volume is present in the drive.  
<p>
On the other hand, if you have inserted 
a different Volume after the last job, and Bacula recognizes
the Volume as valid, it will request authorization from the
Director to use this Volume.  In this case, if you have
set <b>Recycle Current Volume = yes</b> and the Volume is
marked as Used or Full, Bacula will prune the volume and
if all jobs were removed during the pruning (respecting the
retention periods), the Volume will be recycled and used.
For this to work, you must have <b>Accept Any Volume = yes</b>
in the Pool.  The recycling algorithm in this case is:
<ul>
  <li>If the VolStatus is <b>Append</b> or <b>Recycle</b>
      and <b>Accept Any Volume</b> is set, the volume
      will be used.</li>
  <li>If <b>Recycle Current Volume</b> is set and the
      volume is marked <b>Full</b> or <b>Used</b>, Bacula
      will prune the volume (applying the retention period).
      If all Jobs are pruned from the volume, it will be
      recycled.</li>
</ul>
      
<p>This permits users to manually change the Volume every day
and load tapes in an order different from what is in the 
catalog, and if the volume does not contain a current
copy of your backup data, it will be used.


<h2>Recycle Status</h2>
Each Volume inherits the Recycle status (yes or no) from the
Pool resource record when the Media
record is created (normally when the Volume is labeled). This
Recycle status is stored in the Media record of the Catalog.
Using the the Console program, you 
may subsequently change the Recycle status for each Volume.
For example in the following output from <b>list volumes</b>:
<font size=-2>
<pre>
+----------+-------+--------+---------+------------+--------+-----+
| VolumeNa | Media | VolSta | VolByte | LastWritte | VolRet | Rec |
+----------+-------+--------+---------+------------+--------+-----+
| File0001 | File  | Full   | 4190055 | 2002-05-25 | 14400  | 1   |
| File0002 | File  | Full   | 1896460 | 2002-05-26 | 14400  | 1   |
| File0003 | File  | Full   | 1896460 | 2002-05-26 | 14400  | 1   |
| File0004 | File  | Full   | 1896460 | 2002-05-26 | 14400  | 1   |
| File0005 | File  | Full   | 1896460 | 2002-05-26 | 14400  | 1   |
| File0006 | File  | Full   | 1896460 | 2002-05-26 | 14400  | 1   |
| File0007 | File  | Purged | 1896466 | 2002-05-26 | 14400  | 1   |
+----------+-------+--------+---------+------------+--------+-----+
</pre></font>
all the volumes are marked as recyclable, and the last Volume, <b>File0007</b>
has been purged, so it may be immediately recycled. The other volumes are all 
marked recyclable and when their Volume Retention period (14400 seconds or 4 hours)
expires, they will be eligible for pruning, and possible recycling.
Even though Volume <b>File0007</b> has been purged, all the data on the
Volume is still recoverable. A purged Volume simply means that there are
no entries in the Catalog. Even if the Volume Status is changed to 
<b>Recycle</b>, the data on the Volume will be recoverable. The data
is lost only when the Volume is re-labeled and re-written.
<p>
To modify Volume <b>File0001</b> so that it cannot be recycled, you
use the <b>update volume pool=File</b> command in the console program,
or simply <b>update</b> and Bacula will prompt you for the information.
<font size=-2>
<pre>
+----------+------+-------+---------+-------------+-------+-----+
| VolumeNa | Media| VolSta| VolByte | LastWritten | VolRet| Rec |
+----------+------+-------+---------+-------------+-------+-----+
| File0001 | File | Full  | 4190055 | 2002-05-25  | 14400 | 0   |
| File0002 | File | Full  | 1897236 | 2002-05-26  | 14400 | 1   |
| File0003 | File | Full  | 1896460 | 2002-05-26  | 14400 | 1   |
| File0004 | File | Full  | 1896460 | 2002-05-26  | 14400 | 1   |
| File0005 | File | Full  | 1896460 | 2002-05-26  | 14400 | 1   |
| File0006 | File | Full  | 1896460 | 2002-05-26  | 14400 | 1   |
| File0007 | File | Purged| 1896466 | 2002-05-26  | 14400 | 1   |
+----------+------+-------+---------+-------------+-------+-----+
</pre> </font>
In this case, <b>File0001</b> will never be automatically recycled. The
same effect can be achieved by setting the Volume Status to Read-Only.

<h2><a name="singletape">Making Bacula Use a Single Tape</a></h2>
Most people will want Bacula to fill a tape and when
it is full, a new tape will be mounted, and so on.  However, as
an extreme example, it is possible for Bacula to write
on a single tape, and every night to rewrite it. To get this
to work, you must do two things: first, set the VolumeRetention
to less than your save period (one day), and the second item
is to make Bacula mark the tape as full after using
it once. This is done using <b>UseVolumeOnce = yes</b>. If
this latter record is not used and the tape is not full
after the first time it is written, Bacula will simply
append to the tape and eventually request another volume.
Using the tape only once, forces the tape to be marked
<b>Full</b> after each use, and the next time <b>Bacula</b>
runs, it will recycle the tape.
<p>An example Pool resource that does this is:
<pre>
Pool {
  Name = DDS-4
  Use Volume Once = yes
  Pool Type = Backup
  AutoPrune = yes
  VolumeRetention = 12h # expire after 12 hours
  Recycle = yes
}
</pre>

<h2><a name="usageexample">A Daily, Weekly, Monthly Tape Usage Example</a></h2>
This example is meant to show you how one could define
a fixed set of volumes that Bacula will rotate through
on a regular schedule. There are an infinite number of such
schemes, all of which have various advantages and disadvantages.
<p>We start with the following assumptions:
<ul>
  <li>A single tape has more than enough capacity to do
      a full save.</li>
  <li>There are 10 tapes that are used on a daily basis
      for incremental backups. They are prelabeled Daily1 ...
      Daily10.
  <li>There are 4 tapes that are used on a weekly basis
      for full backups. They are labeled Week1 ... Week4.</li>
  <li>There are 12 tapes that are used on a monthly basis
      for full backups. They are numbered Month1 ... Month12</li>
  <li>A full backup is done every Saturday evening (tape inserted
      Friday evening before leaving work).</li>
  <li>No backups are done over the weekend (this is easy to
      change).</li>
  <li>The first Friday of each month, a Monthly tape is used for
      the Full backup.</li>
  <li>Incremental backups are done Monday - Friday (actually
      Tue-Fri mornings).
</ul>
We start the system by doing a Full save to one of the weekly volumes
or one of the monthly volumes.  The next morning, we remove the tape 
and insert a Daily tape. Friday evening, we remove the Daily tape
and insert the next tape in the Weekly series. Monday, we remove the
Weekly tape and re-insert the Daily tape.  On the first Friday of the
next month, we insert the next Monthly tape in the series rather than
a Weekly tape, then continue. When a Daily tape finally fills up,
<b>Bacula</b> will request the next one in the series, and the next
day when you notice the email message, you will mount it and <b>Bacula</b>
will finish the unfinished incremental backup.

<p>What does this give?  Well, at any point, you will have a 
the last complete Full save plus several Incremental saves. 
For any given file your want to recover (or your whole system), you
will have a copy of that file every day for at least the last 14 days.
For older versions, you will have at least 3 and probably 4 Friday
full saves of that file, and going back further, you will have a copy
of that file made on the beginning of the month for at least a year.
<p>So you have copies of any file (or your whole system) for at least
a year, but as you go back in time, the time between copies increases
from daily to weekly to monthly.
<p>What would the Bacula configuration look like to implement
such a scheme?
<pre>
Schedule {
  Name = "NightlySave"
  Run = Level=Full Pool=Monthly 1st sat at 03:05
  Run = Level=Full Pool=Weekly 2nd-5th sat at 03:05
  Run = Level=Incremental Pool=Daily tue-fri at 03:05
}

Job {
  Name = "NightlySave"
  Type = Backup
  Level = Full
  Client = LocalMachine
  FileSet = "File Set"
  Messages = Standard
  Storage = DDS-4
  Pool = Daily
  Schedule = "NightlySave"
}

\# Definition of file storage device
Storage {
  Name = DDS-4
  Address = localhost
  SDPort = 9103
  Password = XXXXXXXXXXXXX
  Device = FileStorage
  Media Type = 8mm
}

FileSet {
  Name = "File Set"
  Include = signature=MD5 { 
    fffffffffffffffff
  }
  Exclude = { *.o }
}

Pool {
  Name = Daily
  Pool Type = Backup
  AutoPrune = yes
  VolumeRetention = 10d   # recycle in 10 days
  Maximum Volumes = 10
  Recycle = yes
}

Pool {
  Name = Weekly
  Use Volume Once = yes
  Pool Type = Backup
  AutoPrune = yes
  VolumeRetention = 30d  # recycle in 30 days (default)
  Recycle = yes
}

Pool {
  Name = Monthly
  Use Volume Once = yes
  Pool Type = Backup
  AutoPrune = yes
  VolumeRetention = 365d  # recycle in 1 year
  Recycle = yes
}
</pre>

<h2><a name="PruningExample">
Automatic Pruning and Recycling Example</a></h2>  
Perhaps the best way to understand the various resource records
that come into play during automatic pruning and recycling is to
run a Job that goes through the whole cycle.  If you add the
following resources to your Director's configuration file:
<pre>
Schedule {
  Name = "30 minute cycle"
  Run = Level=Full Pool=File Messages=Standard Storage=File 
         hourly at 0:05
  Run = Level=Full Pool=File Messages=Standard Storage=File 
         hourly at 0:35
}

Job {
  Name = "Filetest"
  Type = Backup
  Level = Full
  Client=XXXXXXXXXX
  FileSet="Test Files"
  Messages = Standard
  Storage = File
  Pool = File
  Schedule = "30 minute cycle"
}

\# Definition of file storage device
Storage {
  Name = File
  Address = XXXXXXXXXXX
  SDPort = 9103
  Password = XXXXXXXXXXXXX
  Device = FileStorage
  Media Type = File
}

FileSet {
  Name = "Test Files"
  Include = signature=MD5 { 
    fffffffffffffffff
  }
  Exclude = { *.o }
}

Pool {
  Name = File
  Use Volume Once = yes
  Pool Type = Backup
  LabelFormat = &quot;File&quot;
  AutoPrune = yes
  VolumeRetention = 4h
  Maximum Volumes = 12
  Recycle = yes
}
</pre>
Where you will need to replace the <b>ffffffffff</b>'s by the 
appropriate files to be saved for your configuration. For the FileSet Include,
choose a directory that has one or two megabytes maximum since there
will probably be approximately 8 copies of the directory that
<b>Bacula</b> will cycle through.
<p>In addition, you will need to add the following to your
Storage daemon's configuration file:
<pre>
Device {
  Name = FileStorage
  Media Type = File
  Archive Device = /tmp
  LabelMedia = yes;  
  Random Access = Yes;
  AutomaticMount = yes;
  RemovableMedia = no;
  AlwaysOpen = no;
}
</pre>
<p>With the above resources, Bacula will start a Job every half 
hour that saves a copy of the directory you chose to /tmp/File0001 ...
/tmp/File0012. After 4 hours, Bacula will start recycling the backup
Volumes (/tmp/File0001 ...). You should see this happening in the 
output produced. Bacula will automatically create the Volumes (Files)
the first time it uses them.
<p>To turn it off, either delete all the resources you've added, or
simply comment out the <b>Schedule</b> record in the <b>Job</b>
resource.

<h2><a name="manualrecycling">Manually Recycling Volumes</h2>
Although automatic recycling of Volumes is implemented
in version 1.20 and later (see the <a href="recycling.html">Automatic
Recycling of Volumes</a> chapter of this manual),
you may want to manually force reuse (recycling) of a Volume.

<p>Assuming that you want to keep the Volume name, but
you simply want to write new data on the tape, the steps to
take are:
<ul>
  <li>Use the <b>update volume</b> command in the Console to   
      ensure that the <b>Recycle</b> field is set to <b>1</b></li>
  <li>Use the <b>purge jobs volume</b> command in the Console
      to mark the Volume as <b>Purged</b>.  Check by using
      <b>list volumes</b>.</li>
</ul>
Once the Volume is marked Purged, it will be recycled the
next time a Volume is needed.

<p>If you wish to reuse the tape by giving it a new name,
follow the following steps:  
<ul>
  <li>Use the <b>purge jobs volume</b> command in the Console
      to mark the Volume as <b>Purged</b>.  Check by using
      b>list volumes</b>.</li>
  <li>In Bacula version 1.30 or greater, use the Console
      <b>relabel</b> command to relabel the Volume.</li>
</ul>
Please note that the relabel command applies only to
tape Volumes.
<p>
For Bacula versions prior to 1.30 or to manually relabel the
Volume, use the instructions below:   
<ul>
  <li>Use the <b>delete volume</b> command in the Console
      to delete the Volume from the Catalog.</li>
  <li>If the a different tape is mounted, use the <b>unmount</b>
      command, remove the tape, and insert the tape to be
      renamed.</b>
  <li>Write an EOF mark in the tape using the following 
      commands:
<pre>
  mt -f /dev/nst0 rewind
  mt -f /dev/nst0 weof
</pre>
      where you replace <b>/dev/nst0</b> with the appropriate
      device name on your system.</li>
   <li>Use the <b>label</b> command to write a new label to
       the tape and to enter it in the catalog.</li>
</ul>
<p>
Please be aware that the <b>delete</b> command can be dangerous.
Once it is done, to recover the File records, you must either
restore your database as it was before the <b>delete</b> command,
or use the <b>bscan</b> utility program to scan the tape and
recreate the database entries.

<page_prev name="Catalog Maintenance" url="catmaintenance.html">
<page_next name="Backing Up to Disk Volumes" url="disk.html">
