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Automatic Volume RecyclingNormally, 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 recycling volumes, we mean that Bacula can write over the previous contents of a volume. Thus all previous data will be lost.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 Manually Recycling Volumes below in this chapter. 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. By properly defining your Volume Pools with appropriate Retention periods, Bacula can manage the recycling (such as defined above) automatically. Automatic recycling of Volumes is controlled by three
records in the Pool resource definition in the Director's
configuration file. These three records are:
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 "force" Bacula to use
a purged Volume, you must first ensure that no other Volume in the
Pool is marked Append. If necessary, you can manually set a volume
to Full. 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.
Bacula's process for removing entries from the catalog is called Pruning. The default is Automatic Pruning, which means that once an entry reaches a certain age (e.g. 30 days old) it is removed from the catalog. Once a job has been pruned, you can still restore it from the backup tape, but one additional step is required: scanning the volume with bscan. The alternative to Automatic Pruning is Manual Pruning, in which you explicitly tell Bacula to erase the catalog entries for a volume. You'd usually do this when you want to reuse a Bacula volume, because there's no point in keeping a list of files that USED TO BE on a tape. Or, if the catalog is starting to get too big, you could prune the oldest jobs to save space. Manual pruning is done with the prune command in the console. (thanks to Bryce Denney for the above explanation). Prunning DirectivesThere are three pruning durations. All apply to catalog database records and not to the actual data in a Volume. The pruning (or retention) durations are for: Volumes (Media records), Jobs (Job records), and Files (File records). The durations inter-depend a bit because if Bacula prunes a Volume, it automatically removes all the Job records, and all the File records. Also when a Job record is pruned, all the File records for that Job are also pruned (deleted) from the catalog.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. 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. 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. By setting AutoPrune to yes you will permit Bacula 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 Append available, Bacula will begin volume pruning. This means that all Jobs that are older than the VolumeRetention period will be pruned from every Volume that has Volume Status Full or Used and has Recycle set to yes. 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 Purged implying that no Jobs remain on the volume. The Pool records that control the pruning are described below.
Recycling AlgorithmAfter 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 Recycle flag is on (Recycle=yes) for that Volume, Bacula will relabel it and write new data on it.The full recycling algorithm that Bacula uses when it needs a new Volume is:
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 Recycle Current Volume = yes 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 Accept Any Volume = yes in the Pool. The recycling algorithm in this case is:
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. Recycle StatusEach 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 list volumes:+----------+-------+--------+---------+------------+--------+-----+ | 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 | +----------+-------+--------+---------+------------+--------+-----+all the volumes are marked as recyclable, and the last Volume, File0007 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 File0007 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 Recycle, the data on the Volume will be recoverable. The data is lost only when the Volume is re-labeled and re-written.
To modify Volume File0001 so that it cannot be recycled, you
use the update volume pool=File command in the console program,
or simply update and Bacula will prompt you for the information.
Making Bacula Use a Single TapeMost 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 UseVolumeOnce = yes. 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 Full after each use, and the next time Bacula runs, it will recycle the tape.An example Pool resource that does this is: Pool { Name = DDS-4 Use Volume Once = yes Pool Type = Backup AutoPrune = yes VolumeRetention = 12h # expire after 12 hours Recycle = yes } A Daily, Weekly, Monthly Tape Usage ExampleThis 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.We start with the following assumptions:
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. 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. What would the Bacula configuration look like to implement such a scheme? 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 } Automatic Pruning and Recycling ExamplePerhaps 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: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 = "File" AutoPrune = yes VolumeRetention = 4h Maximum Volumes = 12 Recycle = yes }Where you will need to replace the ffffffffff'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 Bacula will cycle through. In addition, you will need to add the following to your Storage daemon's configuration file: Device { Name = FileStorage Media Type = File Archive Device = /tmp LabelMedia = yes; Random Access = Yes; AutomaticMount = yes; RemovableMedia = no; AlwaysOpen = no; } 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. To turn it off, either delete all the resources you've added, or simply comment out the Schedule record in the Job resource. Manually Recycling VolumesAlthough automatic recycling of Volumes is implemented in version 1.20 and later (see the Automatic Recycling of Volumes chapter of this manual), you may want to manually force reuse (recycling) of a Volume.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:
If you wish to reuse the tape by giving it a new name, follow the following steps:
For Bacula versions prior to 1.30 or to manually relabel the Volume, use the instructions below:
Please be aware that the delete command can be dangerous. Once it is done, to recover the File records, you must either restore your database as it was before the delete command, or use the bscan utility program to scan the tape and recreate the database entries.
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