Thin Provisioning Space Reclamation — Avoiding SDelete

Thin provisioning can be a great thing. You get the effect of using more physical resources than are actually available, yet you use less physical storage and spend less money on storage. It’s pretty easy to see the benefits. Often associated with large disk storage systems such as SANs and storage virtualization systems, thin provisioning allows enough space to be easily allocated to servers when that space is needed. So organizations can be smarter about hardware purchases and often defer disk storage purchases. This is a typical scenario when reclaiming thin-provisioned space at the storage level (for example, with HP 3PAR systems).

Over allocation of storage in a thin provisioning environment allows a server to view more storage capacity than has actually been physically reserved for the server. The storage gets used only when needed by an application. This over-allocation is a key benefit of thin provisioning.

But often, data is written on a thin-provisioned drive and then deleted. This can happen at the Windows OS level, rather than at the hardware level. This occurs with thin-provisioned virtual disk drives. And in this situation, there’s a good chance you want that space back. But you typically can’t get the space back — it’s not available to use because the blocks that were previously written need to be zeroed out first. While there are ways to do this, it’s not easy. Probably the most popular method is Microsoft’s SDelete command-line utility.

But SDelete can be slow. Very slow. And cumbersome. It is, after all, a manual, command-line utility that by its very nature (manual) is prone to error. In speaking with many organizations, we’ve actually found that many storage and system administrators eschew even attempting to use SDelete, feeling it’s just not worth the aggravation. So what do they do instead? They may end up buying more storage, offsetting some of the benefits they were striving for with thin provisioning.

Others have turned to PerfectDisk’s Zero Fill feature to automate the reclamation of free space in a thin provisioned environment. With PerfectDisk’s Zero Fill, you can easily zero-fill free clusters on a drive manually with just one click or on a scheduled basis.

But it gets better.

Better would be automatic detection of free clusters via a pre-determined schedule or via a certain percentage of free clusters on a thin provisioned drive that have not been zero-filled. And then have zeros written to those free clusters, or automatically issue the SCSI Unmap command to accomplish the task, if your hardware supports SCSI Unmap. Better would be never having to think or worry about SDelete again.

Help for thin provisioning space reclamation is here today with PerfectDisk’s Zero Fill.

And even more help is on its way.

Arriving in 2013.

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