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Thin Provisioning and Reclamation, Veritas Storage Foundation/ETERNUS DX

February 2, 2010

The Thin Provisioning functions of ETERNUS disk storage systems allow more efficient use of storage capacity by virtualizing the storage space.

Thin Provisioning allocates space virtually rather than physically, based on the demands of users. The resulting virtual volumes are logically independent of the physical storage and so the physical storage does not need to be fully allocated initially.
Physical storage is only allocated to the virtual volumes when they actually require an increase in physical data capacity.
This means Thin Provisioning allows disk drives to be more efficiently and dynamically added to the storage system. Plus the expansion of physical capacity is more gradual and consolidated across the requirements of all virtual volumes rather than separately for each volume.
For further details on Thin Provisioning, see "Storage capacity virtualization "Thin Provisioning""

To further reduce the use of physical storage capacity, Veritas File System (VxFS), a part of Veritas Storage Foundation, is used with ETERNUS DX to allow physical capacity, no longer needed by the virtual volumes due to data deletion, to be dynamically retrieved.

Veritas File System (VxFS) has the largest share of the global dynamic physical disk reduction market.

If enough available capacity is created by deleting or compressing data using ETERNUS Thin Provisioning and Veritas Storage Foundation, disk use efficiency can be further increased by returning the available spare capacity to the shared disk pool.

The following figure shows an example of dynamic physical disk reduction.
In this example, it is assumed that a 10TB virtual volume was user allocated but only 2TB of physical disk has so far been required.
The spare capacity of the allocated 2TB physical disk is returned to the shared disk pool by deleting File-A and File-C.

veritas storage foundation

The following figure shows the difference in required physical disk storage capacity between where dynamic physical disk reduction is supported and where it is not.
The capacity required by Systems A and B change over time, both increasing and decreasing. When dynamic physical disk reduction is not supported, it is necessary to secure physical disk with a total capacity equal to the maximum capacity so far required by both systems. But when dynamic physical disk reduction is supported, it is only necessary to secure physical disk with a capacity equal to the current total capacities of both systems.
This can significantly reduce the requirement for physical disks.


- Reduced business investment by more efficient control and use of physical disk space.
- No need for special operations to expand or reduce storage capacity (automatically reflected)
- Reduced physical disk addition from improved usage efficiency by reuse of existing physical disks

Product Requirements

Storage System ETERNUS DX80 S2/DX90 S2
ETERNUS DX400/DX400 S2 series
ETERNUS DX8000 series/DX8700 S2
Software Veritas Storage Foundation
Threshold monitoring ETERNUS SF Storage Cruiser or ETERNUSmgr