Raytheon E-Systems, Inc.
                                 501 S. Jupiter Road
                                  Garland, TX 75042

                                    19 August 1998

Advanced Digital Information Corporation
11431 Willows Road N.E.
Redmond, WA 98073


Ladies and Gentlemen:


     We refer to that certain Stock Purchase Agreement ("Stock Purchase
Agreement") dated as of July 21, 1998 between Raytheon E-Systems, Inc.
("Raytheon") and Advanced Digital Information Corporation ("ADIC") by which ADIC
will purchase from Raytheon all the stock of EMASS, Inc., a Delaware
corporation ("EMASS"). Unless otherwise defined herein, all capitalized terms
used herein shall have the meanings assigned in the Stock Purchase Agreement. As
a condition precedent to closing the sale of EMASS, Section 5.10 of the Stock
Purchase Agreement requires that Raytheon cause the discharge of all obligations
under certain loan agreements ("Grau Loan Agreements") between EMASS/Grau
Storage Systems GmbH & Co. KG [KG], a limited partnership organized under the
laws of Germany, and Deutsche Bank and Commerzbank, respectively.

     In order to close the purchase of EMASS on Wednesday, the 19th of August 
1998, Raytheon has estimated the amount necessary to discharge all 
obligations under the Grau Loan Agreements on the date hereof and has 
purchased and transferred such estimated amount (US$8,721,208.33, which 
amount shall be referred to herein as the "Estimated Payoff Amount") to the 
respective banks. The Estimated Payoff Amount shall be the amount used by 
Raytheon and ADIC as the "Current Portion--LT Debt" in determining the 
Adjusted Purchase Price in accordance with Sections 2.4(a)(i) and 2.4(a)(iii) 
of the Stock Purchase Agreement.

     ADIC agrees to use its best efforts to forthwith discharge, or cause the
discharge of, the Grau Loan Agreements and the associated Raytheon guarantees
and to forthwith provide Raytheon with proof of such discharge. ADIC also agrees
to indemnify and hold harmless Raytheon for any claims or liabilities arising on
or after the date hereof with respect to the Grau Loan Agreements or the
associated Raytheon guarantees.




     Kindly indicate your agreement with the terms of this letter by signing in
the space indicated below.


                                        Yours very truly,


                                        RAYTHEON E-SYSTEMS, INC.


                                        By /s/ Michael C. Eberhardt
                                          -------------------------
                                          Michael C. Eberhardt, Vice President,
                                             Secretary and General Counsel


Acknowledged and agreed.

ADVANCED DIGITAL INFORMATION CORPORATION

By /s/ Leslie S. Rock
  ---------------------------




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