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Unfortunately, it isn't an ideal world. The SMI-S interoperability standard is a step in the right direction but in its present version "there appears to be more missing from SMI-S v.1 than [what] is in it," says Gartner's Passmore. "The value-added features unique to each storage device will always emerge in front of the standards. Managing these features will require non-SMI-S tools or nonstandard extensions to SMI-S," he notes.
Even storage virtualization doesn't eliminate vendor lock-in. "The hype suggests virtualization is great, but we haven't seen that," says Passmore. "The only way to avoid vendor lock-in today is to utilize lowest common denominator storage."
Theoretically, virtualization could help, but it comes with a lot of "ifs." In Gartner's mixed storage report, Passmore writes: "If the virtualization box replaces the value-added software in the back-end arrays, and contains its own cache, then having those features in the back-end arrays is a waste of money. And if the user is using a virtualization box to gather up existing arrays, then the investments already made would be lost for the remaining life of the box. This leads to a simple conclusion about the disk behind arrays--it should be basic RAID disk, without volume management, snapshots, replication, cache or any other features that would be duplicated in the higher-end array." And those basic disks should be put into the virtualizing array to avoid the added cost of another cabinet with
Virtualization ultimately negates the advantage of a multiple vendor strategy. "The variation in price between vendors offering comparably configured arrays is mostly found in the value-added software and services," Passmore notes. "This means that most of the cost advantage gained from multiple storage vendor deployments will disappear when the software is single-sourced in the virtualization box."
Savvis Communications, a Town & Country, MO-based IT infrastructure managed services provider, turned to what it refers to as virtualization to help lower its storage costs as part of an initiative to reduce overall infrastructure costs. "Virtualization lets us decouple a logical service like storage from the physical implementation," says Bryan Doerr, Savvis' CTO.
Doerr's approach puts all the storage capacity--220TB at last count--in a single pool and then uses thin provisioning, not virtualization, to allocate the storage as needed. Virtualization usually describes capabilities that mask the differences among various vendors' arrays, but Savvis is provisioning disk within a single vendor's--3PAR Inc.--array. Other vendors, such as Zetta Systems Inc. (acquired by Overland Storage Inc.) and Network Appliance Inc., with its FlexVol capabilities, offer thin provisioning.
"We can create logical volumes for a customer, but we only allocate actual disk to the customer as it's being written," Doerr explains. Customers pay only for the storage capacity they actually use. This lets Savvis avoid having to overprovision each customer's storage, which can save the company money.
This was first published in February 2006