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                                                             EXHIBIT 21

                                    EXHIBIT A

                 RELEVANT SUBSIDIARIES OF PARENT HOLDING COMPANY

PART A: TCW ENTITIES

PARENT HOLDING COMPANY:

      The TCW Group, Inc.

      Robert Day (an individual who may be deemed to control The TCW Group,
      Inc.)


RELEVANT SUBSIDIARIES THAT ARE PERSONS DESCRIBED IN RULE 13d-1(b):

        (i)   Trust Company of the West, a California corporation and a bank as
              defined in Section 3(a)(6) of the Securities Exchange Act of 1934.

        (ii)  TCW Asset Management Company, a California corporation and an
              Investment Adviser registered under Section 203 of the Investment
              Advisers Act of 1940.

        (iii) TCW Investment Management Company, a California corporation and an
              Investment Adviser registered under Section 203 of the Investment
              Advisers Act of 1940.

Note:   No Common Stock of Read-Rite Corporation is held directly by The TCW
        Group, Inc. Other than the indirect holdings of The TCW Group, Inc., no
        Common Stock of Read-Rite Corporation is held directly or indirectly by
        Robert Day, an individual who may be deemed to control The TCW Group,
        Inc.

PART B: NON TCW ENTITIES

PARENT HOLDING COMPANY:

         Robert Day (an individual who may be deemed to control the entities
         described below which are not subsidiaries of The TCW Group, Inc.)

RELEVANT SUBSIDIARIES THAT ARE PERSONS DESCRIBED IN RULE 13d-1(b):

         Oakmont Corporation, a California corporation and an Investment Adviser
         registered under Section 203 of the Investment Advisers Act of 1940.


                                       A-1



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