Mass storage array with efficient parity calculation

An efficient redundant array of mass storage devices comprising:

• a plurality of hard disk drives;
• a host computer, and said host computer periodically supplying new data to said hard disk drives;
• at least one bus interconnecting said host computer and each of said hard disk drives;
• a controller coupled to each of said hard disk drives;
• each of said disk drives containing old data previously stored on said disks, and said hard disk drives also containing old parity, which is parity relating to said old data;
• partial parity calculating means which is the Exclusive Or function of old data and new data;
• said hard disk drives, each having its own controller means for calculating the new parity which is the Exclusive Or function of partial and old parity;
• and
• means for communicating the partial parity from said partial parity calculating means to said controller means.

A computer system including an efficient, redundant array of mass storage devices comprising:

• a host computer;
• a plurality of hard disk drives;
• at least one bus interconnecting said hard disk drives and said host computer;
• each of said disk drives containing parity data previously stored on said disks;
• and
• a plurality of controllers coupled respectively to said plurality of disk drives including means for calculating parity data by calculating the Exclusive Or function of partial parity data and old parity data.