Time based data retention in a variable data rate disk drive

A method for assuring that the desired data is transferred between a disk drive and an exterior environment during read or write operations, comprising the steps of:

• providing a disk having a plurality of concentric tracks onto which data sectors may be written, said tracks each being divided into an equal number of data regions separated from one another by servo sample regions, wherein the number of data sectors stored in each data region varies between at least two of said plurality of concentric tracks;
• providing a spindle motor for rotating said disk at a substantially constant velocity;
• providing a read/write head for sensing data from a track of said disk during a read operation and for inducing data into a track of said magnetic disk during a write operation;
• providing head location means for locating said head over a desired track of said magnetic disk in response to a signal from an exterior environment;
• providing a variable data rate channel for reading data from and for writing data to said disk, the data rate of said channel depending upon the number of data sectors stored in each data region of said desired track;
• providing buffer means, located between said channel and said exterior environment, for providing temporary storage of data as said data sectors are being transferred between said disk and said exterior environment during read and write operations, said buffer having a predetermined number of storage locations for storing a predetermined number of data sectors;
• transferring data sectors between said disk and said exterior environment;
• receiving and storing data sectors being transferred between said disk and said exterior environment, in said buffer means;
• retaining a number of data sectors in said buffer means after said data sectors have been transferred between said disk and said buffer means, for possible retransfer between said disk and said buffer means, before releasing corresponding storage locations in said buffer means for the storage of new data sectors;
• and
• adjusting the number of data sectors retained by said buffer means in said retaining step based on the number of data sectors transferred between said disk and said buffer means in a substantially fixed time period for providing efficient data transfer rate performance between said disk and said exterior environment.

An apparatus for assuring that the desired data is transferred between a disk drive and an exterior environment during read and write operations, comprising:

• a magnetic disk onto which data may be written in the form of magnetic polarity transitions, wherein said magnetic disk includes a first concentric data track with a first radius and a second concentric data track with a second radius that is greater than said first radius, said first concentric data track containing less data than said second concentric data track over the same angular distance;
• a spindle motor for rotating said magnetic disk at a substantially constant angular velocity;
• means for transferring data between said disk and said exterior environment, wherein said means for transferring data includes means for transferring data with said first concentric data track at a first data rate and said second concentric data track at a second data rate that is greater than said first data rate;
• buffer means, located between said means for transferring and said host system, for providing temporary storage of data as said data is being transferred between said magnetic disk and said exterior environment, said buffer being capable of storing a predetermined amount of data;
• data retaining means for retaining an amount of data in said buffer means for a predetermined period of time after said data has been transferred between said disk and said buffer means, for possible retransfer between said disk and said buffer means, before releasing corresponding data storage locations in said buffer means for the storage of new data;
• buffer control means for adjusting the amount of data being retained by said data retaining means based on a substantially fixed time period for providing efficient data transfer rate performance between said magnetic disk and said exterior environment.