Expiring backup data when destination has been moved to new location (backup to disk)
I have a question regarding freeing up my current disk backup space as the data protection of backup jobs expires.
As i understand Data Protector's expiring and deleting of old backup content off of disk when protection has expired, this happens the next time the backup job runs. My question is, if I modify the destination to another backup to disk location, how will the old backup content be expired and deleted if it no longer writes to the same location?
I hope my question is understood.
The medium information in DP Media Management Database contains information about its physical location. Expiration process uses this physical location to delete the underlying storage file. Physical location of existing media does not change if you modify the library to use a different destination for new backups. This allows the expiration to delete old backup content even if you change the library to use different destination.
there are a multitude of options in DP subsumed under the "Backup to Disk" moniker, you have to be more specific. Everything based on B2D devices (e.g. StoreOnce Software or Catalyst) will use a dedicated scheduled purge of expired media that doesn't depend on any backups running to a given store, so it's not a problem here. What you describe applies to File Libraries, though (both classic and DFMF). Expired media would be purged as a first step of every session writing towards a File Library device, so moving all backup or copy sessions away from said FL (leaving it only for restore purposes) would just cause the data to linger there forever. I used to schedule an unprotected dummy backup towards such FLs if cleaning them up timely was necessary, as in FL-to-SOS migration scenarios involving the same destination file systems.
Yet another B2D scenario is when using a VTL, and that one really can get complicated. The only way to "free" expired media in a VTL (in the sense of telling the VTL it's now gone and can be deleted) is by overwriting the media, which naturally doesn't happen when no more sessions are running against it - it already starts to become a problem when the traffic towards a VTL dwindles and the backlog of expired-but-not-yet-overwritten media grows. There's usually not much you can do here except manual intervention (removing media in the VTL and replacing it by blank media). If the VTL pool is non-appendable (which it should be, at least for StoreOnce) a dummy backup writing roughly the right number of media as before might do the trick, as VTapes will be protected, but essentially empty with dedup doing the rest.