Looking for disk in all the wrong places


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It's all about efficiency
Rather than utilization per se, we should focus on storage efficiency; each transformation level represents an important component of an overall efficiency metric. Efficiency targets should be established at each level to ensure these goals are met. The goal is to minimize the light-colored parts of the bars on the chart wherever possible.

This chart highlights the primary responsibilities at each stage of storage allocation:

Source: GlassHouse Technologies

The capacity reduction resulting from data protection policies (physical to logical) is owned primarily by the storage architect, who must translate business data protection requirements into standard storage configurations that support those policies.

The storage admin is responsible for allocating storage based on user requests, while the system admin assigns and makes storage available to applications. Unclaimed storage is a handoff issue between storage and system admins, and each must bear some responsibility in the process. Finally, file-system and database utilization may be the shared responsibility of the application owner and the system admin depending on the environment. These responsibilities can vary greatly from one organization to another.

Other functional areas can play a significant role, too. For example, the speed of the purchasing group's acquisition process directly impacts the reserve of allocated

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storage maintained by a storage administrator, so purchasing should share some of the responsibility for meeting target levels. What are the appropriate target levels for each category? Unfortunately, the classic consultant's answer, "It depends," applies. However, this graph shows some sample targets:

Source: GlassHouse Technologies

Clearly the physical-to-logical gap is policy based, and will have different values depending on the storage tiering structure. The allocated-to-claimed ratio should be close to zero in most cases. The remaining areas depend on organizational variables and the time impact of things like the change management and purchasing processes.

Assigned vs. written represents traditional file-system utilization, which brings us back to where we started--the basis for the initial storage request. The more accurate the size estimates here, the lower the overall multiple.

Gathering and reporting the efficiency information is also a challenge. The data is typically dispersed throughout the organization and no single tool currently provides it all. Developing a mechanism for collecting these metrics will likely require a cross-functional effort. It may not be easy, but it's essential to tame the storage consumption monster.

This was first published in July 2006

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