Forum Discussion

Tabriz's avatar
Tabriz
Level 5
4 years ago

the differention between The Policy and SLP

Hi,

l confuse one thing.For example l make a policy for backup. Therefore l need special storage for backup files.Then l make a SLP and l need seperate tape (volume pool). for deduplication l need one more tape pool.after retention in which volume pool the data expire.How going on this procedure generally

Thanks

  • Short answer, data never exists in a volume pool, and so isn't deleted from a volume pool.

    Long answer ...

    Backup policy contains a Storage Unit (tape or disk) and the policy also has a retention period - how long to keep the data on the disk or tape - if tape, you also set the volume pool to use, where the volume pool is just a 'group of tapes'.

    When using an SLP, you specify the SLP name in the backup policy, in place of the storage unit name.

    The SLP itself contains the different storage units and retention periods you wish to use for the backup and duplication. So it's really no different to how a backup works, just that there are multiple copies.

    Typically, data is written to disk and kept for say 1 week, or a month.  The duplicated copy usually goes to tape and is kept for a longer period of time.

    Data never exists in a volume pool as such, it exists only on tape, but the tapes are grouped in a volume pool.

    The tape volume pool is just to group tapes for a particular use, for example file system backup, oracle backups, catalog backups would be different pools.  The volume pool isn't even referenced for a restore, we only need the mediaID (be it disk or tape).   When an image expires it is deleted from the catalog and when all the images expire from a tape, the tape is available for re-use, and they will then be overwritten.  Once a tape 'expires' it willl either stay in the same volume pool, or be moved back to scratch pool if that is set up.  (There is an exception that if the tape was manually put into a volume pool, it will stay there, and not revert back to the scratch pool.)

    If an image that expires is on disk, the same happens, it is deleted from the catalog but the difference compared to tape, is that it is almost instantly deleted from the disk.    As tape is sequential, this is not possible, hence the images stay on the tape, until it is overwritten (bonus of this means you have a higher chance or importing an image from tape that was accidently expired).

  • X2's avatar
    X2
    Moderator

    Backup policy is just what it says - how, when, who, what to backup.

    SLP = how the backup images are managed till they expire. You need to have a plan wherein you can say something simple like:

    • Do a backup of a client on STU1 (copy1). ret=2weeks
      •      Then duplicate the backup image to STU2 (copy2), ret type: exipre after copy
        •      Then duplicate to tape - STU1 -> Tape1 (copy3) ret=3months; make primary, expire copy1
        •      and STU2 -> tape2 (offsite) (copy4) ret=3months, expire copy2

    Identation shows hierarchy of operations in the SLP. So, second operation starts only after first is successfully completed. Then 3rd and 4th start at same time. The complexity depends on how many copies are needed, on which storage and what is your retention criteria. Once it is set, you can use the SLP as Policy storage in your backup policy.

    I normally start without NetBackup terminology i.e. in plain words and sentences. Once that is hashed out, then it becomes simple enough to create the SLP as per the requirement. SLPs are well worth the time to spend creating properly. They are like shut it and forget it type operation. Start reading the SLP section in the Admin guide.

     

     

  • What X2 said :-)

    In general keep the number of tape pool down to the minimum. A pool contain diffrent retentios, keep the number of retentions as low as possible.

    Too many diffrent tape pools and too many  retention will kill tape effeincy.

     

    • Tabriz's avatar
      Tabriz
      Level 5

      on SLP configuration we need  storage for backup (disk pool or other advancedDisk) and for the duplication we need volume pool(from tape library).That is okay.But l confuse this procedure after retention expire the data is deleted from disk pool but is not deleted from wolume pool ?in our company there is such strategy every week we change tapes (in one week we use for example 86 100) another week we use (42 24) and t continues like this with the same tapes.if so, where the data is collected and stored

      Thanks

      • mph999's avatar
        mph999
        Level 6

        Short answer, data never exists in a volume pool, and so isn't deleted from a volume pool.

        Long answer ...

        Backup policy contains a Storage Unit (tape or disk) and the policy also has a retention period - how long to keep the data on the disk or tape - if tape, you also set the volume pool to use, where the volume pool is just a 'group of tapes'.

        When using an SLP, you specify the SLP name in the backup policy, in place of the storage unit name.

        The SLP itself contains the different storage units and retention periods you wish to use for the backup and duplication. So it's really no different to how a backup works, just that there are multiple copies.

        Typically, data is written to disk and kept for say 1 week, or a month.  The duplicated copy usually goes to tape and is kept for a longer period of time.

        Data never exists in a volume pool as such, it exists only on tape, but the tapes are grouped in a volume pool.

        The tape volume pool is just to group tapes for a particular use, for example file system backup, oracle backups, catalog backups would be different pools.  The volume pool isn't even referenced for a restore, we only need the mediaID (be it disk or tape).   When an image expires it is deleted from the catalog and when all the images expire from a tape, the tape is available for re-use, and they will then be overwritten.  Once a tape 'expires' it willl either stay in the same volume pool, or be moved back to scratch pool if that is set up.  (There is an exception that if the tape was manually put into a volume pool, it will stay there, and not revert back to the scratch pool.)

        If an image that expires is on disk, the same happens, it is deleted from the catalog but the difference compared to tape, is that it is almost instantly deleted from the disk.    As tape is sequential, this is not possible, hence the images stay on the tape, until it is overwritten (bonus of this means you have a higher chance or importing an image from tape that was accidently expired).