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The Storage Diet

Thin provisioning works wonders for ensuring every application gets a healthy portion of disk space.

Storage administrators know the drill: Someone in the organization needs extra capacity allocated to a new application. How much is enough? Most end up overallocating to cover both current and estimated future needs, resulting in wasted capacity that’s seldom used.

Enter thin provisioning, a software technology built into storage hardware from manufacturers such as EMC, Hewlett-Packard, IBM, LeftHand Networks and NetApp. Known also as dynamic provisioning and flexible volumes, thin provisioning allows administrators to initially allocate a large amount of virtual storage to an application while reserving only a fraction of actual disk space. Designed to either increase the physical capacity automatically as the need increases or notify the administrator of the need for more physical disk space, thin provisioning stretches storage and extends the life of existing storage systems.

“Storage thin provisioning is such a valid concept because it allows users to properly utilize their storage resources,” says Deni Connor, principal analyst at Storage Strategies Now. “Customers don’t have to go out and buy more storage when they see they are running out, and the [database administrator] comes to them and says, ‘I need another terabyte of storage.’”

That scenario rings true for Raymond Meyers, a network administrator at the Wilmington-based Delaware Division of Revenue. Meyers has too many memories of adding Microsoft Windows servers on the fly to meet pressing storage demands. He now takes advantage of thin provisioning to dole out smaller slices of his LeftHand SAN for everything from Oracle database development to data growth stemming from the division’s now-public tax database.

Meyers reckons thin provisioning has allowed him to defer the purchase of more storage capacity by more than a year, leaving funds to purchase a new rack of switches instead. “It also literally granted me the ability and the budget to pull off other projects rather than investing in hardware,” he says. “Some projects are directly possible due to the SAN and thin provisioning, such as creating test databases, test environments and purchasing virtual servers without ever having to buy a new server.”

Storage-related activities such as provisioning, backup and moving data account for 20 percent of IT labor costs, according to a report from F5 Networks.

Heading off additional infrastructure purchases also prompted Gaston County, N.C., to tap thin provisioning. Chief Information Officer Brandon Jackson’s SAN supports data-intensive applications such as a geographic information system, an SQL Server database and an Exchange mail server. “Thin provisioning allows us to allocate a minimal amount of space, but grow space dynamically whenever and however we need to,” he says.

Pairing thin provisioning with storage and server virtualization amounts to significant savings for the county. “We’re saving about $78,000 a year in server infrastructure procurement and support,” says Jackson. “That doesn’t seem like a lot of money, but it translates into 20 percent of our server and storage budget.”

Under the Hood

To achieve optimal performance, pay attention to these details:

  • Software specifics. Determine how your applications treat thinly provisioned storage. A few apps could consume the entire virtually allocated space at once, negating potential savings.
  • How big or small? Consider the maximum size of the logical unit number (LUN) that can be provisioned. Also, determine the smallest data block you can start with or add later.
  • Check the ratios. Different storage architectures follow certain thin-provisioning ratios. SAN or NAS environments might employ a 3-1 ratio (three times the storage capacity provided to an application while only one-third is thin provisioned). Direct-attached storage (DAS) might follow a 2-1 ratio.
  • Location matters. Check where thin-provisioned data is located. Placement on outer disk spindles can improve data access speed. Placement on different storage tiers can also affect performance.
Sep 30 2008