The Free On-line Dictionary of Computing (30 December 2018):

constant linear velocity

    (CLV) A way of controlling the rotation of the disks
   in a disk drive in which the linear velocity of the disk
   surface relative to the read/write heads is kept constant.

   In order to achieve constant linear velocity, the disk must rotate
   faster (at a higher angular velocity) when reading or writing
   tracks closer to the centre.

   Having a constant linear read/write speed along the track means
   that the electrical signal to and from the heads has a constant
   data rate (bits per second), thus simplifying the timing of the
   drive electronics somewhat.  However, rotating at less than the
   maximum possible rate sacrifices some potential performance
   compared to the alternative, constant angular velocity.  Also,
   varying the rate causes more vibration and consumes more energy.

   (2014-07-27)