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).