Storage Utilization

I am frequently asked about the utilization of storage, and it seems that when there are more than three people in the room, it can become a highly confusing subject. Depending on the perspective, it can be difficult to agree on exactly what utilization is being measured. While the storage administrators will declare a utilization number, procurement management will profess another, and an outside consulting company might state yet a different utilization number. This all leads to executive management being confused. Why isn't everyone on the same page?

Storage utilization is represented as a percentage of the whole of something. The fundamental issue is that there are many different terms used for the different stages of storage. Basically, the stages of storage and high-level definitions are:

1.Raw the physical disk purchased

2.Configured – RAID is applied

3.Allocated – provisioned to the hosts4.Claimed – received by the host

5.Assigned – presented to the end user as a filesystem or raw disk for a database

6.Used – data written to disk by the end user or an application

As disks are prepared for the end user's purpose they pass through the stages listed above.

Of course, many different terms are used for each of these stages. For example, allocated is sometimes referred as provisioned; configured is sometimes called usable; provisioned is sometimes referred to as used; and so on. You can appreciate how confusing this can be. To provide clarity, I recommend agreeing on what word will be used to define a particular stage within the organization. The words that are applied to the definition are likely to be different from organization to organization but the stages do not change.Because the stages of storage are defined, the utilization of storage can now be clearly measured based on what stage is being referenced. Instead of just asking about the utilization of storage, the utilization of a stage of storage over stage of storage (as a percentage) can be understood because of the common reference. Now when the storage administrator (interested in utilization of allocated over configured), the procurement management (interested in utilization of configured over raw), the outside consulting company (perhaps interested in utilization of used over raw) and executive management discuss "storage utilization" there exists a common reference as to the perspective. Now everyone in the room can be on the same page.