![]() Space reclamation uses the 'write same' SCSI command and requires Version 5.0 MP3 of Veritas Storage Foundation and a 3PAR Thin Persistence license for the InServ Storage Server. This new software product from 3PAR is designed to enable InServ arrays to use granular file system-level information to autonomically reclaim unused space within thin InServ volumes so that they stay thin over time. When virtual, full or remote copy snapshots are deleted, freed contiguous 128MB blocks are reclaimed from the TPVV and returned automatically to the CPG for reuse by other volumes.ģPAR worked with Symantec on a Thin Reclamation API that allows a host file system to intelligently communicate with the InServ to reclaim space associated with file deletions. The difference from thin persistence is that space from retired or deleted snapshots can be deleted without the process of sweeping for zero-filled space. With Thin Copy Reclamation, the entire snapshot is returned to the common provisioning group (CPG). When virtual or remote copy snapshots are deleted, space is reclaimed from the TPVV and returned automatically to the array for reuse by other volumes. Thin Copy Reclamation allows free space to be regained when individual snapshots are deleted, thus reducing storage capacity costs by reclaiming storage capacity that is locked up in allocated snapshot space. ![]() Only deltas changes are created from the previous snapshot. By contrast, 3PAR's snapshot technology is reservationless and does not create duplicate copies of data. Multiple copies of the snapshot will exist and disk space consumed. Traditionally, snapshot space is reserved and when snapshots are taken they are duplicative. The significance of thin persistence is in not having to grow volumes to free up space.ģPAR's Thin Copy Reclamation feature of the InForm operating system operates much like thin persistence, except it is for snapshots rather than volumes. Thin Persistence can be used to reclaim this deleted space from the Thin Volumes. If another 20GB is written to the file system, the file system will consume 110GB, while the storage array unaware that data has been deleted, will show 120GB. If 10GB of data is deleted on the host file system, the array has no knowledge of the deletion. ![]() As data is written to the host file system it is also written to the InServ array. If, however, there are applications that continually write and then delete data, thin persistence works best.Ĭonsider this scenario: The host file system has 100GB of data written to it, an amount that is matched by the InServ volume. Typically, applications have storage capacity that grows exponentially – for those applications, thin provisioning works well. Thin persistence keeps a volume from growing when there are a large number of deletes and writes. Freed 16KB blocks are returned to the existing volume as free space. In thin persistence, standard file system tools reclaim allocated but deleted blocks in the user space and write zeros into the blocks. ![]() Thin persistence enables the detection of contiguous strings of zeros to re-thin already thinned volumes. Thin Persistence is 3PAR's ability to reduce the space consumption of a thin provisioned virtual volume (TPVV) in real-time, results in reduced storage costs by allowing thinly provisioned volumes to stay 'thin' – it's like putting your storage on a maintenance diet and not having to worry about what the array stores - the array will stay thin. This newsletter discusses Thin Persistance, Thin Copy Reclamation and Thin Copy Reclamation with Veritas Storage Foundation. 3PAR introduced its 'thin' strategy earlier this week at Storage Networking World. It's keeping storage volumes thin and being able to reclaim storage space. For 3PAR, staying thin is more than just thin provisioning.
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