Storage costs are rising dramatically. That’s especially true for enterprises using Oracle’s performance and capacity-hungry databases. Cash-strapped IT organizations often resort to thin provisioning to squeeze extra capacity from their storage systems.
However, thin provisioning, alone, is inadequate: It can’t free space that’s been de-allocated, or otherwise deleted at the application level. And over time, capacity is eroded. To maintain those space savings, Oracle has added a new capability to its Automated Storage Management (ASM) feature. But not all storage vendors have found an elegant solution to this tricky problem.
It used to be that if a tablespace shrank – or if an entire database was removed from an Oracle ASM disk group – the freed up capacity could not be reclaimed and then reallocated. Oracle’s new Storage Reclamation Utility – ASRU for short – was built to free up space from an Oracle ASM disk group.
But, storage arrays were not designed to detect when ASRU has freed up space. To do that, storage vendors had to add a “reclaim” operation to their systems. With reclaim, a new SCSI command tells the array which regions on a LUN (logical unit number) have been de-allocated after an application deletes file space, allowing the space to be re-used. Oracle ASRU frees up space by writing in “zeros;” however reclaim requires an additional process to find that additional capacity.
Thin Provisioning: The Nimble Approach
Nimble Storage thin provisioning and Oracle ASRU offer an elegant approach to space reclamation. That’s because Nimble opted for a different approach to reducing storage erosion called “zero detection.” Using zero detection, Nimble’s firmware automatically classifies blocks written with zeros as de-allocated.
As a result, database administrators don’t have to run SCSI reclamation to de-allocate blocks when tablespace shrinks, or an entire database is removed. Without any additional work, Nimble allows IT professional to capitalize on the capacity savings achieved through its version of thin provisioning. Nimble works with Oracle’s ASM to claim unused (but allocated) disk space automatically and non-disruptively.
Nimble Storage thin provisioning is supported, and has been validated for both Oracle’s Database 11g Release 2 and 12c Release 1.