May 07 2009

The Storage Diet

Thin provisioning works wonders for ensuring every app 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 over-allocating 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 lets administrators initially allocate a large amount of virtual storage to an app while reserving only a fraction of actual disk space. Designed to either increase the physical capacity automatically as need increases or notify the administrator of the need for more physical 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.’”

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.

The concept of storage virtualization is far from new. “That is what a logical volume manager has done for all OSes for 20 years or more: virtualized a physical disk into a logical disk,” says Richard Jones, vice president and service director for data center strategies at the Burton Group.

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 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 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.