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Why ILM is so difficult
ILM is more than simply moving data to another type of disk within the array or to a different storage subsystem or tape. "Tiered storage is not ILM, although it is a piece of ILM," says Michael Peterson, program director for the Storage Networking Industry Association's (SNIA's) Data Management Forum (DMF). Rather, "ILM is an information-based management practice that uses information about the data as a central actor for setting policies about what to do with the data," he explains. Those policies can specify performance requirements, retention periods, security needs, service levels and more. Seen in this light, "ILM transcends storage," he says.
In short, ILM describes a management process for moving data based on its value to the organization and its need for protection, availability, speed of access and other services. "ILM is a conceptual state in which data is stored in accordance with its changing business value," says Stephen Foskett, director of strategy services, GlassHouse Technologies Inc., Framingham, MA.
To do this, you need to know the data's value, which isn't as simple as you might think. It requires sophisticated metrics that go beyond aging or frequency of access. "You have to take into account the relevance of the data to the core business and the risk of the data not being available," explains Foskett. Determining the relevance of the data to the business may be the hardest part, and it's a task IT can't
Bill Rhyme is manager of support services at a major transportation company. His firm embarked on an ILM initiative six months ago and is still struggling with determining its data's value. "We have the data classified into various categories, but even that doesn't tell us what it is. We're surprised at how much effort even this takes," says Rhyme. The company hopes to have an ILM strategy by the end of the year and to begin implementing pieces of it next year.
For ILM to work across the entire data center, companies need systems that store data based on a unique, meaningful name and meta data stored separately from the data's storage address. That way, data can move to any storage address and the applications can still find it. "Today, we store and access data according to its address and expect it to be there," says Foskett. "If the data is moved, the applications can't find it."
This was first published in July 2006