By Sonia R. Lelii, Senior News Writer, SearchStorage.com | Jan 6, 2011
Thin provisioning still has its detractors, but the technology has made it into the mainstream and can play a prominent role as storage efficiency needs become more important. The technology is still evolving with recent advances around thin reclamation, and administrators say following best practices help avoid problems with under-provisioning.
Thin provisioning, pioneered by small vendors such as 3PAR (now part of Hewlett-Packard Co.) and Compellent Technologies (now part of Dell Inc.) that have been acquired by larger companies, is a method of allocating storage to servers on a just-enough and just-in-time basis.
According to the TheInfoPro's most recent 2010 end-user survey, approximately 51% of Fortune 1000 and midsized enterprise IT organizations use thin provisioning, with 25% piloting or planning to implement thin provisioning. Fewer than 25% say they don't plan to use it. Thin provisioning ranks as the number two technology behind Information Lifecycle Management (ILM) on the analyst firm's Heat Index, said Marco Coulter, TheInfoPro's managing director of storage.
"According to our Heat Index, a number of people are still exploring the technology, but this is where the profession is going," Coulter said.
As hot as thin provisioning is, Gestalt IT consultant Steve Foskett warns it's still not for everyone. Foskett admits there have been improvements to the technology in recent years around reclamation but said de-allocating storage can still be a problem.
"Hosts have no concept of thin provisioning," he said. "All they know is, 'This is my storage.' That's all the hosts have been able to know. People are tempted to use thin provisioning to overallocate storage. And once you have written data to disk, it's difficult to reclaim it. I'm not a fan of a capability that's not effective. If there's a way to allocate and not a way to de-allocate, then it's not effective. I'm concerned people would use it as a band aid for a business problem. People are tempted to use thin provisioning to overallocate storage. Once you've written data to a disk, it's difficult to reclaim it."
Symantec Corp., working with 3PAR and other vendors, in recent years has made improvements in the thin reclamation process. Dan Lamorena, director in Symantec's Storage and High Availability Group, said the software vendor can reclaim storage blocks not being used and put them back in the storage pool.
"We have thin reclamation because we have visibility into our file system," he said. "Reclamation is an issue, but it's not the issue. People worry they haven't provisioned enough storage. They honestly don't know how much storage is being consumed. They don't know how much the application is using."
HP's 3PAR, Compellent, EMC Corp., Hitachi Data Systems, IBM, NetApp and others support Symantec's Thin Reclamation API in their arrays. 3PAR also has what it calls an ASIC-based zero detection mechanism that essentially reclaims unused disk capacity. 3PAR made a thin conversion feature available in Sept. 2009 that makes fat volumes thin when migrated off a legacy array.
Administrators using thin provisioning say they take steps to make sure it remains effective over time. They often carefully track their storage usage, monitoring how much storage they have used over a period of a year or more. They project how much their storage will grow in the coming years, and give their systems a certain percentage of overallocated storage as a buffer to make sure they're not going to be caught underprovisioning.
Brandon Jackson, CIO of Gaston County in North Carolina, has used thin provisioning for five years now on his Compellent Technologies Storage Center system. He said he turned to thin provisioning when he first implemented a SAN because he knew Gaston County's storage needs would grow significantly but he didn't know by how much. Gaston County has two 70 TB Storage Center SANs.