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Spindle Speed

The drive's spindle speed is not a performance measure per se, but it is a characteristic of the drive that is very important in determining how well the drive will perform. In fact, it is one of the better "single numbers" in terms of its reliability in being an indicator of overall hard disk performance: in virtually every case a hard disk that runs at 7,200 RPM is going to offer better performance than one running at 5,400 RPM. In this regard, it is in my opinion far more useful than knowing the rated seek time of the drive, for example. It is also a readily available statistic and easy to determine for any drive.

The reason why spindle speed is so important is that it directly impacts both positioning time and data transfer. The impact on positioning time is through reduction in latency; the impact on data transfer rate is direct because the heads can only read from the disk at the rate they spin past them. This means that faster spindle speed drives will have improved performance regardless of whether they are used for many small, random accesses, or for streaming large contiguous blocks from the disk.

Next: Areal Density

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