The time taken for the read/write heads of a disk drive to be positioned over a required track. Average seek time is the time to reach any track from the center track. Maximum seek/positioning time is the time to reach any track from any track. A high performance modern hard disk offers around 4 ms average seek time and typically twice that for the maximum. Minimum seek time to adjacent tracks is as low as 0.2 ms for read, 0.4 ms for write. These times are critical to disk performance, especially when operating with the very high data rates associated with video and digital film. Many long seek times can degrade performance when using a fragmented disk, so slowing the access to data.
Solid State Drives also have seek times, and their performance can degrade with fragmentation. However SSD technology has very much lower seek times, and generally provides very speedy performance.