Seek Time

Dennis Faas's picture

Seek time is one of the several delays associated with reading or writing data on a computer's disk drive.

In order to read or write data in a particular place on the disk, the read/write head of the disk needs to be moved to the correct place (just as to play a particular song on a cassette of recorded music, the tape needs to be wound to the right place). This process is known as "seeking", and the time it takes for the head to move to the right place is the "seek time". Seek time for a given disk varies depending on how far the head's destination is from its origin at the time of each read or write instruction; usually one discusses a disk's average seek time.

As of 2004, a typical seek time for a hard disk is about 9 ms. Hard disc drives achieve this speed by having a small, lightweight head assembly. Floppy disk drives and optical drives (such as CD or DVD drives) have much larger head assemblies than hard discs, resulting in them having longer seek times. Solid state disks, or SSDs, can have seek times of under 0.1 ms because there are no moving parts to align.

One way to improve seek time (with respect to data acquisition) is to use a defragging utility [see: Magic Defrag]. Because data is randomly stored on a hard disk, a defragging utility resolves this problem [temporarily] by moving related data into close proximity; thus, the seek time required to move the read/write head to related data is significantly reduced. This ultimately results in lower seek time and a gain in performance.

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