Deduplicatation operates by working out if a chunk that is part of a backup is already stored in deduplication
If a match is found we incrementa a count against the chunk and a reference to the backup set, where each backup set has an expiry time for when it wil be reclaimed (deleted)
As the backup sets are reclaimed each chunk that makes up the set will have the reference remevd and the count decremeted by 1
A chunk can only be deleted once it has a count of 0 (and I think may take 24 hours to be deleted unless manual action is taken due to how teh garnage collection operates)
As can be seen there is no guaranee that expiring the sets will get back the equivalent amount of disk space (as a chunk might be needed by another set) and the above process has nothing to do with the disk space reserve setting (all this setting does is set a threshold for alerting against and/orblocking further use of the deduplication folder.
If you want to get back space you therefor have to
- Expire any sets that you no longer need (this is the Backup Exec 2012 and later replacement for step 1 in the below document which was written for Backup Exec 2010 and earlier)
- Follow Step 2 and onwards in http://www.veritas.com/docs/000007234
