Recording Density

Recording density refers to the number of bits that can be placed along a given length of track on a hard disk. Measured in bits per inch, and also sometimes called bit density, linear density or linear areal density--the last term being an oxymoron of sorts!--it is one of the two components of areal density. You can read about it in more detail here.

Recording density is an important performance factor because it is related to both of the "positioning plus transfer" specifications: areal density and spindle speed. Obviously, since it is a component of areal density, it is directly proportional to areal density. As such, it directly or indirectly affects both the access time of the drive and its sustained transfer rate, sometimes in more than one way. How does it influence spindle speed? Well, as explained here, increases in recording density can limit the ability of the drive's spindle motor to be increased--or vice-versa, a faster spindle may requires the recording density to be reduced on the drive to ensure reliability.

Recording density itself is increased primarily through advances in media materials, improved platter substrates, and improved read/write head technologies.

Next: Read/Write Head Technology