<PAGE>

                                                                  EXHIBIT 10.13


                             BOX HILL SYSTEMS CORP.

August 2, 1999

161 Avenue of the Americas
New York, NY  10013

RE:  EMPLOYMENT TERMS

Dear Dana Kammersgard:

Box Hill Systems Corp., a New York corporation (the "Company"), is pleased to
offer you employment on the following terms.

You will serve as Chief Technical Officer and will be responsible for such
duties as are normally associated with such positions. During your service
with the Company, you will devote substantially all of your business time to
the Company. You will report to the Chief Executive Officer(s) and will be
subject to the direction and policies from time to time reasonably
established by the Chief Executive Officer(s).

You will work out of our principal offices located in Carlsbad. You will be
expected to travel as reasonably required by your duties. The Company will
reimburse you for your reasonable travel, entertainment, business and other
expenses incurred in the course of your employment in accordance with Company
policy.

You shall receive an initial base salary of $250,000 per year, payable in
regular periodic payments in accordance with Company policy, less required
payroll deductions and withholdings. The Compensation Committee of the Board
("Compensation Committee") shall determine any changes to your base salary.
You will be entitled to not less than 4 weeks of paid vacation per year, in
addition to all Company holidays.

Upon meeting all applicable eligibility requirements, the Company will
provide you with a competitive comprehensive benefits package including
health and dental insurance. The Company will also pay for health and dental
insurance for your spouse and children under the age of 21. You will be
eligible to participate in the Company's 401(k) plan and the Company's equity
incentive plans. In addition to the foregoing, you will receive all benefits
the Company may provide from time to time to other senior executive level
employees.

You shall be eligible to receive a performance bonus. The award of any
performance bonus shall be at the discretion of the Compensation Committee.
Attached as Exhibit C are the bonus levels and criteria for the remainder of
fiscal year 1999, and the year 2000.

After December 31, 2000, your base salary and annual bonus levels will be
subject to changes as determined by the Committee.

Your employment with the Company will be at-will in that you may terminate
your employment with the Company at any time and for any reason whatsoever.
Likewise, the Company, by a

<PAGE>

August 2, 1999
Page 2

written resolution duly adopted by a majority of the Board, may terminate
your employment at any time and for any reason whatsoever. This at-will
arrangement may not be changed except by a writing signed by you and a duly
authorized officer of the Company.

Upon termination of your employment with the Company, you will be paid your
then current accrued base salary to and including the date of termination,
any accrued vacation pay and other benefits through the date of termination
and all compensation previously deferred by you, if any (together with
accrued interest and earnings thereon).

In addition, if the Company terminates your employment without Cause (defined
below) or you resign for Good Reason (defined below), then so long as (i) you
(or your representative) shall have furnished to the Company an executed
release and waiver of claims in the form attached hereto as Exhibit A (the
"Release") and (ii) the Effective Date provided for in the Release shall have
occurred, the Company shall pay to you, in a single lump sum payment, an
aggregate amount equal to one hundred percent (100%) of your then current
annual base salary, with such payment to be made concurrently with the
Effective Date provided for in such executed Release (subject to required
payroll deductions and withholdings).

If your employment with the Company is terminated for Cause or you resign,
other than for Good Reason, you shall not be entitled to receive any
compensation following such termination other than salary and vacation
accrued on or prior to the termination date and any reimbursement expenses
due to you for which you shall not have been previously reimbursed.

For the purposes of this letter agreement the following definitions shall
apply:

     (1)  "Cause" shall be limited to the occurrence of any of the following
events, as set forth in a written resolution duly adopted by a majority of
the Board: (i) your personally continuing to engage in conduct which causes
material harm to the Company after having been given thirty (30) days written
notice of such determination by the Board (ii) your indictment for violation
of any Law constituting a felony (including the Foreign Corrupt Practices Act
of 1977) or the foreign equivalent thereof, (iii) your continuing failure to
perform the lawful directives of the Board (consistent with the terms of this
letter) or your duties and responsibilities hereunder, in each case in all
material respects and after having been given thirty (30) days written notice
of such determination by the Board which written notice shall specifically
identify the directive alleged not to have been followed or the provision of
this letter which it is alleged you have continually failed to substantially
perform, the basis for the Board's determination thereof and the specific
corrective action that the Board proposes that you take; and (iv) your
incurable breach of any material element of the Company's Confidential
Information and Inventions Agreement. In no event shall your death or
disability constitute Cause or the basis for any termination therefor;

     (2)  "Good Reason" shall mean (i) a reduction in your base salary, (ii)
the relocation of your full-time office to a location other than within sixty
miles of Carlsbad, (iii) a violation or breach by the Company, in any
material respect, of any of its obligations under this letter so long as you
have given the Company thirty (30) days notice of such breach, and the
Company has not cured the breach during that thirty (30) day period.

     (3)  "Disability" shall mean your failure or inability, for reasons of
health, to perform your usual and customary duties on behalf of the Company
in the usual and customary manner

<PAGE>

August 2, 1999
Page 3

for a total of more than 90 consecutive business days (excluding Saturdays,
Sundays and Holidays (days during which the Company is closed due to a
recognized a holiday)).

In the event of any termination of your employment with the Company other
than for death or Disability, the Company shall have the right to retain you
as a consultant for a period of one (1) year from the date of such
termination (the "Consulting Period"). During the Consulting Period, the
Company shall be entitled to require you to be available to render consulting
services for up to twelve (12) days of consulting during such one (1) year
period, it being understood that the scheduling of such consulting services
shall not interfere with your work schedule for your principal employer. The
Company shall schedule such consulting for days, or portions thereof, and
places reasonably satisfactory to you, and unless you otherwise agree, all
consulting services shall be rendered in Carlsbad. In exchange for your
availability during the Consulting Period (whether or not the Company
actually schedules consulting activities), the Company shall pay you, in four
(4) equal payments (the "Consulting Payments"), an aggregate amount equal to
twenty-five percent (25%) of your annual base salary in effect as of the date
of your termination, with the first such payment to be made within five (5)
business days following commencement of the Consulting Period and the next
three (3) payments to be made on the first day of each successive calendar
quarter following the date of termination. The Company shall also reimburse
you for your reasonable expenses incurred in carrying out your consulting
duties hereunder.

During the time that you are employed by the Company pursuant hereto, and
during the Consulting Period, but (without limitation of your rights and
remedies under this letter agreement) only for so long as the Company
continues to employ you in accordance with the terms hereof or make
Consulting Payments in accordance with the immediately preceding paragraph,
as the case may be, you will not, without the Company's prior written
consent, directly or indirectly, (i) own, manage, operate, control or
participate in any material way in the ownership, management, operation or
control of, whether as an officer, employee, partner or otherwise, any
business which directly competes with the business of the Company or (ii)
solicit or induce any employee of the Company to leave the employ of the
Company (it being understood that placing "help-wanted" or similar ads in
newspapers or other media of general circulation or distribution shall not
constitute such a solicitation or inducement); provided that nothing in this
letter agreement shall restrict you from at any time (A) engaging in any
business where your primary focus is not computer storage, whether as an
owner, manager, operator, officer, employee, partner, control person or
otherwise or (B) beneficially owning less than two percent (2%) of the
outstanding equity interests in any publicly traded company.

The Company will indemnify you for all damages and costs that may be incurred
by you in connection with claims arising out of or relating to your acts or
omissions within the authorized scope of your employment. The Company shall
provide such indemnification, and shall advance your expenses incurred in
connection with any such claims as reasonably requested by you and as duly
approved by the Board from time to time, to the fullest extent permissible
under applicable law.

As a Company employee, you will be expected to abide by Company rules and
regulations. As a condition of employment, you will be required to sign and
comply with a Confidential Information and Inventions Agreement, a copy of
which is attached hereto as Exhibit B, which, among other things, prohibits
unauthorized use or disclosure of Company proprietary information.

<PAGE>

August 2, 1999
Page 4

The employment terms in this letter supersede any other agreements or
promises made to you by anyone, whether oral or written, and comprise the
final, complete and exclusive agreement between you and the Company. As
required by law, this offer is subject to satisfactory proof of your right to
work in the United States.

Please sign and date this letter, and return it to me as soon as possible if
you wish to accept employment at the Company under the terms described above.

We look forward to your favorable reply and to a productive and enjoyable
work relationship.

Sincerely,

BOX HILL SYSTEMS CORP.

By:    /s/ Philip Black
       -------------------------

Name:  Philip Black

Title:  CEO

ACCEPTED BY:


/s/ Dana Kammersgard
----------------------------
    Dana Kammersgard


----------------------------
        Date


<PAGE>

                                   EXHIBIT A

                          RELEASE AND WAIVER OF CLAIMS

     In consideration of the payments and other benefits set forth in my
employment offer letter, to which this form is attached, I hereby furnish Box
Hill Systems Corp. (the "Company") with the following release and waiver.

     I hereby release, and forever discharge the Company, its officers,
directors, agents, employees, stockholders, successors, assigns and
affiliates, of and from any and all claims, liabilities, demands, causes of
action, costs, expenses, attorneys' fees, damages, indemnities and
obligations of every kind and nature, in law, equity, or otherwise, known and
unknown, suspected and unsuspected, disclosed and undisclosed, arising at any
time prior to and including my employment termination date with respect to
any claims relating to my employment and the termination of my employment,
including but not limited to, claims pursuant to any federal, state or local
law relating to employment, including, but not limited to, discrimination
claims, claims under the California Fair Employment and Housing Act, and the
Federal Age Discrimination in Employment Act of 1967, as amended ("ADEA"),
the Federal Americans with Disabilities Act ("AD") or claims for wrongful
termination, breach of the covenant of good faith, contract claims, tort
claims, and wage or benefit claims, including but not limited to, claims for
salary, bonuses, commissions, stock, stock options, vacation pay, fringe
benefits, severance pay or any form of compensation.

     I also acknowledge that I have read and understand Section 1542 of the
California Civil Code which reads as follows: "A general release does not
extend to claims which the creditor does not know or suspect to exist in his
favor at the time of executing the release, which if known by him must have
materially affected his settlement with the debtor." I hereby expressly waive
and relinquish all rights and benefits under that section and any law of any
jurisdiction of similar effect with respect to any claims I may have against
the Company.

     I acknowledge that, among other rights, I am waiving and releasing any
rights I may have under ADEA, that this waiver and release is knowing and
voluntary, and that the consideration given for this waiver and release is in
addition to anything of value to which I was already entitled as an employee
of the Company. I further acknowledge that I have been advised, as required
by the Older Workers Benefit Protection Act, that: (a) the waiver and release
granted herein does not relate to claims which may arise after this release
and waiver is executed; (b) I have the right to consult with an attorney
prior to executing this release and waiver (although I may choose voluntarily
not to do so); and (c) if on the date of execution of this release and waiver
I am age 40 or older, then (I) I have twenty-one (21) days from the date I
receive this release and waiver, in which to consider this release and waiver
(although I may choose voluntarily to execute this release and waiver
earlier); and (II) I have seven (7) days following the execution of this
release and waiver to revoke my consent to this release and waiver. This
release and waiver shall be effective as of the date of execution hereof;
provided that if on the date of execution of this release and waiver I am age
40 or older, then this release and waiver shall not be effective until the
foregoing seven (7) day revocation period has expired. The date as of which
this release and waiver is effective as aforesaid shall be deemed the
"Effective Date" hereof.


Date:                                  By:
     ------------------                   ------------------------------------

<PAGE>

                                   EXHIBIT B

               CONFIDENTIAL INFORMATION AND INVENTIONS AGREEMENTS

For purposes of this Agreement, "Box Hill" shall include Box Hill Systems,
Corp., Artecon, Falcon, Storage Dimensions and any past, present or future
subsidiaries of those companies.

In consideration for my employment by Box Hill:

1.   I will not disclose to anyone outside of Box Hill, or use in other than
     Box Hill's business for the benefit of Box Hill any Box Hill
     Confidential Information or material relating to the business of Box
     Hill either during or after my employment at Box Hill, except with Box
     Hill's written permission. I also understand that information and
     materials received in confidence from third parties by Box Hill and its
     subsidiaries is included within the meaning of this paragraph.

2.   I will not disclose to Box Hill, or induce Box Hill to use, any
     confidential information or material belonging to others.

3.   I will comply, and do all things necessary for Box Hill to comply, with
     United States Government regulations and with provisions of contracts
     between the agencies of the United States Government of their
     contractors and Box Hill, which relate either to patent rights or to the
     safeguarding of information pertaining to the defense of the United
     States.

4.   I hereby assign to Box Hill my entire right, title and interest in any
     invention or idea, patentable or not, hereafter made or conceived solely
     or jointly by me:

     a.   While working at Box Hill in an executive, managerial, planning,
technical, research or engineering capacity (including development,
manufacturing, systems, applied science, sales or customer engineering); and

     b.   That relates in any manner to the actual or anticipated business of
Box Hill or to Box Hill's actual or anticipated research and development, or
is suggested by or results from any task assigned to me or work performed by
me or on behalf of Box Hill; except any invention or idea which I cannot
assign to Box Hill because of prior invention agreement with
____________________ which is effective until ____________________ (give name
and date or write "none")

5.   I agree that in connection with any invention or idea covered by
     paragraph 4

     a.   I will disclose it promptly to the Box Hill Management; and

     b.   I will, at Box Hill's request, promptly execute a specific
assignment of title to Box Hill, and do anything else reasonably necessary to
enable Box Hill to secure patent therefor in the United States and in foreign
countries.

6.   I represent that I have indicated on the back of this form any
     inventions or ideas, not covered in paragraph 4, in which I have any
     right, title or interest, and which were previously conceived either
     wholly or in part by me, but neither published nor filed in the United
     States Patent Office, and identified all of these.

<PAGE>

7.   I agree to comply with Box Hill's Database Policy. The policy states
     that all information in databases, whether centrally located (e.g. Minx
     or Informix) or locally (e.g. Act!) are the property of Box Hill Systems
     and are considered confidential. This information includes but is not
     limited to customer contacts, customer lists, pricing, inventory,
     vendors, billing, shipping and customer service data. I will not
     transfer, reproduce or duplicate this confidential information outside
     of the Box Hill. This includes, but is not limited to, transmitting
     database information by email, transferring the information verbally or
     by hardcopy, or any other means. Additionally, I will not intentionally
     destroy any information in central or local databases.

8.   I understand and acknowledge that any breach of my obligations under
     this agreement will result in irreparable harm to Box Hill and hereby
     consent to the entry of injunctive relief to prevent or restrain any
     further violation of or harm to Box Hill's rights.

9.   I acknowledge receipt of a copy of this agreement, and agree that with
     respect to the subject matter hereof, it is my entire agreement with Box
     Hill, superceding any previous oral or written communications,
     representations, understanding or agreements with Box Hill or any
     official or representative thereof.


Signed:
                       -------------------------------------------------------
Employee's Full Name:
                       -------------------------------------------------------
Witness:
                       -------------------------------------------------------
              (Employee's Manager or other appropriate Box Hill representative)
Date:
                       -------------------------------------------------------


<PAGE>

                                   EXHIBIT C

QUARTERLY PERFORMANCE BONUS

Each quarter, you shall be eligible for a performance bonus of up to 50% of
your base salary for such quarter (Quarterly Bonus). The Quarterly Bonus
shall be based on the following formula, and on the Company's Business Plan,
as approved by the Board of Directors, for such quarter:

FORMULA

1.   REVENUE-BASED BONUS: Half of the Quarterly Bonus shall be based on
revenue. If the Company meets the Business Plan revenue goals for any given
quarter, you shall be entitled to half of the Quarterly Bonus (25% of your
base salary for such quarter) for performance during the quarter. If the
Company fails to meet the Business Plan revenue goals for a given quarter,
then the revenue-based bonus shall be paid as follows:

     if the Company attains less than 75% of the Business Plan revenue goals,
     you shall not receive any revenue-based bonus for that quarter. For
     attaining levels of revenue between 75% and 100% of plan, you shall
     receive 2% of the total Quarterly Bonus for every 1% of revenue above
     75%.

2.   INCOME-BASED BONUS: Half of the Quarterly Bonus is to be based on net
income. If the Company meets the Business Plan net income goals for any given
quarter, then you shall be entitled to half of the Quarterly Bonus (25% of
your salary for such quarter) for performance during that quarter. If the
Company fails to meet the Business Plan net income goals for a given quarter,
then the net income-based bonus shall be paid as follows:

     0.5% of the Quarterly Bonus, payable for each 1% achieved of the net
     income line of the Business Plan, up to a maximum of 100%.

BUSINESS PLAN DETERMINATIONS

Third Quarter, 1999: You shall be granted full bonus (50% of base salary).

Fourth Quarter, 1999: You shall be granted a bonus pursuant to the formula
set forth above, based on the Business Plan for the Fourth Quarter, to be
approved by the Board during the Fourth Quarter.

Fiscal Year 2000: You shall be granted bonus pursuant to the formula set
forth above, based on the Business Plan for the Year 2000, to be approved by
Board during the First Quarter of 2000.