1. Thin Conversion. Slims down “stout” storage volumes as they are moved to a thin environment.
2. Thin Copy Reclamation. Reclaims unused space from snapshot or replicated volumes.
3. Thin Reclamation for Veritas Storage Foundation. Integrates with VxVM to release deleted data from the array.
4. Thin Persistence. Dynamically releases deleted data from active volumes.

Now I thought InServ arrays already had this functionality but maybe I was jumping the gun when I mentioned thin support in recent posts.  However, that said, the ability to thin-on-the-fly is undoubtably a good one.  ZPR from Hitachi/HP requires the “offline” collection of freed blocks.

What interests me most is the detail around Thin Persistence.  The description in the  flyer for the feature makes the following claim:

“Thin Persistence achieves [the thinning of volumes] by using the built-in zero detection capability embedded in the 3Par Gen3 ASIC to reclaim unused space associated with deleted data within the InServ storage volumes”

Now correct me if I’m wrong but I thought most data deletions were done at a logical level, releasing only pointers in the appropriate file system tables.  If this is so, how does the system identify this space as reclaimable?  Is there a new “super-delete” facility that writes binary zeros over deleted files?  Alternatively I guess we could write a “block-scrubber” which allocates free space into a psuedo-file, writes zeros over it and releases it.  Of course the ultimate place for this kind of feature is the defragmenter.  As blocks are re-organised, overwrite free space with binary zeros the first time they are moved  That way the problem is solved.

Can anyone from 3Par shed light on my mis-understanding of the above?