The big switch
SOME CONCEPTS ABOUT managing storage quickly capture our attention before making a fast fade in the light of harsh reality. A year or so ago, the idea of creating a utility storage environment was a hot topic, but it seems to have been relegated to the back burner after an onslaught of catchier acronyms and technologies.
Most of the big storage vendors jumped into the utility fray with a variety of offerings that expanded on the original definition of utility storage. But oversimplification may have had more to do with the fleeting interest in the concept than the concept itself. Vendors made utility storage sound great--dial in the capacity when you need it and flip off the switch when you don't.
Storage that flows like water or electricity, and a big on/off switch to control it all, is an appealing notion. But the idea of utility storage isn't all that analogous to the public utilities we're familiar with. Water and electricity flow into and out of our homes and offices as needed, but that's where the similarities end. You have little control over those utilities--you can start and stop them, and draw a little or a lot off the grid.
Unfortunately, storage isn't that easy. Tapping into more or less capacity is fine, and can help some shops stabilize storage costs over the long haul, but most companies need more than just a volume control. The type and quality of the storage is also likely to be a factor, including its performance and reliability.
Even the term "utility" needs some qualification. There are two types of utility storage: internal utilities that mete out already installed capacity, and external services that more closely resemble the public utility model. On the service side, perhaps the most successful utility-oriented vendors are those that provide offsite backup storage and related services. Sun Microsystems touts its Sun Grid, which offers pay-as-you-go computing at a fixed rate of $1 per CPU hour, which includes 10GB of what Sun calls "high-performance storage."
Other vendors, such as Hewlett-Packard and IBM, have long offered on-demand utility storage. In an on-demand scenario, the vendor installs an array with a well-stocked supply of disk and the user can "turn on" additional capacity as needed. Vendors monitor usage and charge accordingly; in some cases, storage that's been used can later be turned off and the charges reduced. We've also seen one-off deals from vendors that don't publicly market utility options. But the hook here is that fees are often based on the price of the fully installed storage, so while pay-per-use pricing can spread out the cost, it may not reduce the total tab in the end.
There are a few reasons why the idea of utility storage hasn't taken off. To effectively use it, a company has to do a lot of legwork. Utility models are based on service-level agreements (SLAs)--to accurately apportion storage and ensure that you're not paying too much for it, you have to have a good idea of the specific needs of the business units and apps that will use the utility. Many companies today work with SLAs to establish and meet the expectations of internal users, but SLAs for utility storage add another dimension that can profoundly effect how much a company spends on storage. An internal storage utility requires some degree of virtualization and is ultimately just a better method of managing SLAs and charging back for consumption.
When the storage utility is a service that provides offsite storage, data security concerns may also undermine the utility concept. It takes a significant leap of faith to trust a vendor with your company's crown jewels.
But the biggest barrier to utility storage is the same thing that makes storage vendors prosper: spiraling storage growth and its relentless demands on capacity. There hardly seems to be a need for an on/off switch when a shop's storage switch is permanently stuck in the "on" position.