RAID Arrays

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A further complexity in the optimization picture comes in the form of hardware and software RAID. Although they make use of multiple physical disks, volume sets and stripe sets appear to the operating system as a single logical drive. Again, it becomes extremely difficult to predict the exact location of the center or outside edge of RAID arrays. While RAID employs as many as five platters, a highly simplified example of a two-spindle disk (Exhibit 5) is used here. The cluster numbers are shown, extending from 0 to 23 on disk 1 and then continuing from 24 to 47 on disk 2. With only two disks, the concept of a physical beginning, middle, and end begins to look questionable. Now add three more disks, and the concept becomes almost absurd. In the words of my Microsoft contact, you may be playing probabilities and perhaps you should think twice before gambling with user data and system performance.

Exhibit 5: Two-Spindle Disk

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