CHAPTER 22

The Cache Layer

The disk drive’s cache is a great equalizer of performance. It can reduce the net performance gap between two drives with a vast difference in raw performance capability such as seek time and rotational speed. Cases exist in which a mechanically slow desktop or even mobile drive whose caching strategy is better tuned for certain applications outperforms a much faster server drive whose cache is not designed to handle those applications. Caching is, therefore, a key factor in a disk drive’s performance, whose importance is equal to other basic drive attributes such as seek time, rotational speed, and data rate.

Because of its importance, this chapter is devoted to disk cache exclusively. There are two aspects to the ...

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