Magnetic: Hard disk storage systems continue to benefit from technological advances. Contemporary systems can reliably accommodate up to 800 Mbytes of data, and access times for such high capacity disks have dropped to 20 msec or less (Kalstrom, 1989). Hard disk systems are relatively inexpensive mass storage solutions, and the increased reliability and miniaturization of components has made them more appropriate for portable applications. Additionally, the use of perpendicular recording technologies will make low cost, high capacity magnetic disks available with the capability to store 10 times more data per inch than now permitted (Ozawa, 1986). Data Storage