CHAPTER 3

MAGNETIC DISK TECHNOLOGIES

David A. Thompson

INTRODUCTION

Magnetic hard disk technology is the undisputed leader for online storage applications, i.e., for storing data inexpensively, but in such a way as to be available within a time period less than human response times. Although the time delay for the first data bit to become available is thousands of times longer than for semiconductor memory, the data (when it does arrive) streams from the disk at tens of megabytes per second. The cost of hard disk storage is a few cents per megabyte, which is several orders of magnitude less than for semiconductor memory.

Tape storage is cheaper than disk storage, but its access time is much longer. It is possible to configure optical storage for online applications, but such a system is inferior to hard disk storage in every respect: cost, data rate, access time, etc. Only by moving to a library configuration or a data interchange application, which both utilize the removability of optical media at the expense of access time and mechanical complexity, does optical storage find a successful niche in which it can compete. There is at this time no technology that appears to have a chance of displacing hard disk storage in the next 10 years.

One major difference between hard disk and interchange media like tape and disk is the effect that standards and the need for backward compatibility have on the rate of technological progress. Hard disk standards involve external attributes of the drive only: physical size, power, cooling, and the data bus protocol and connector. There is no need for the customer to know what technology is being used to store and retrieve data within the box.

The situation with interchange media is different. The customer is vitally interested in his ability to read old formats and share media with other customers. There is also a benefit from utilizing standards from the audio and video entertainment industries. As a result, almost all of the tape media progress is spill-over from the much larger entertainment market, and many of the optical storage standards are based on compatibility with audio or video players.

This difference is also reflected in the nationality of the companies that manufacture disk drives. As recently as 1997, U.S.-based companies produced about 80% of the revenues and an even greater fraction of the hard disk drive (HDD) units sold. This is just the opposite of the situation in tape and optical storage, where Japanese and other Asian companies dominate the business for both entertainment and for computer storage devices (see Fig. 3.1 and Tables 3.1-3.3).


Fig. 3.1. U.S. and non-U.S. HDD market share per year (ASET/SRC, Miura, March 1998).

From this data, one might expect that Japan is not a center of HDD technology. This impression is completely false! Consider the following observations:

Other examples of a rising Japanese presence can be seen by a few months of press clippings (Table 3.4), by the order in which companies have brought magneto resistive (MR) heads to the marketplace (Table 3.5), and in the areal density being shipped as of May 1997 (Table 3.6).

Table 3.1
Share of HDD Market by National Origin, 1995
 

United States

Japan

Other

U.S. Share (%)

HDD Revenue ($ million)

$22,722

$3,610

$250

85.5

HDD Units (million)

79.5

8.4

2

88.4


Source: Gourevitch et al. 1997
Table 3.2
Location of HDD Final Assembly, 1995 (% of units)

United States

Southeast Asia

Japan

Other-Asia

Europe

Total

4.6

64.2

15.5

5.7

10.0

100


Source: Gourevitch et al. 1997
Table 3.3
Geographic Distribution of the Wage Bill (%)
 

United States

Japan

S.E. Asia

Europe

Other

Percent of Total

42.2

23.9

12.9

6.2

14.8


Source: Gourevitch et al. 1997
Table 3.4
Recent Headlines-Typical Press Clippings

Date

Headline

5/18/98

Hitachi to Begin Mass-producing GMR Heads

5/13/98

Hitachi Announces a 6.48 GB GMR Mobile HDD

5/12/98

Toshiba Formally Announces a 6.4 GB GMR Mobile Drive

4/18/98

HITACHI Announces 3.5", Half-High, 12000 rpm 9.1 GB Hard Disk Drive

4/15/98

Fujitsu Introduces Three New Mobile Hard Drives

3/06/98

Integral files for Bankruptcy

2/27/98

HITACHI Reveals New HDAs

2/04/98

Mitsumi Electric to Enter the Magneto-Resistive (MR) Head Race

2/03/98

Fujitsu to Incorporate GMR Head Technology in Disk Drives

1/23/98

HITACHI Announces 12,000 rpm High-End hard Disk Drive

1/22/98

Seagate Exits the Mobile HDD Business

1/20/98

Hitachi Announces New 2.5" Mobile Hard Disk Drives

5/13/98

Hitachi Metals to Sample GMR Heads in February

The connection between the HDD industry and the Japanese universities has been weak for many years, but the recent establishment of the Storage Research Consortium (SRC) has begun the process of building the sort of ties in Japan that exist in the United States and Singapore.

Table 3.5
Introduction of MR Heads by Company

Company

Month (or Quarter)

Year

IBM

May

1991

Fujitsu

February

1994

Seagate

1Q

1994

Hitachi

June

1994

Quantum

October

1994

Hewlett Packard

4Q

1995

NEC

1Q

1996

Micropolis

December

1996

Maxtor

4Q

1996


Source: Disk/Trend Report as reported by ASET
Table 3.6
Current Areal Density by Company

Company

Areal Density (Mb/in2)

IBM

2,638.0

Hitachi

2,013.0

Quantum

1,646.0

Toshiba

1,308.0

Fujitsu

1,300.0

Maxtor

1,193.0

Seagate

1,108.0

JTS

1,008.0

Micropolis

959.2

Samsung

884.0


Published: June 1999; WTEC Hyper-Librarian