Exhibit 10.10

April 15, 2009

Peter Slocum

Dear Peter:

On behalf of 3PAR, Inc., (the
Company), I am pleased to offer to you the exempt position of Vice President, Engineering reporting to David Scott, President/CEO. In accepting this offer of employment you agree to start your employment at the earliest during the week
of April 20, 2009 and no later than April 27, 2009.

Should you accept this offer your compensation will include:



| |  |  | A base salary of $230,000.00 per year of which will be paid biweekly in accordance with the Companys normal payroll procedures. The first
and last payment by the Company to you will be adjusted, if necessary, to reflect a commencement or termination date other than the first or last working day of a pay period.
| | - |  | -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------



| |  |  | In addition you will be eligible for the FY2010 (April 1, 2009-March 31, 2010) Executive Bonus if payouts under Bonus Plan are approved by the
Board for the upcoming fiscal year.
| | - |  | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------



| |  |  | We will recommend to the Compensation Committee of the Companys Board of Directors after commencement of your employment that you receive a grant
of options with respect to the 200,000 shares of common stock of the Company, and your grant will be subject to the approval of the Compensation Committee or its delegate. Your grant will be priced in accordance with our equity incentive
plan and our policies governing stock option grants.
| | - |  | -----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

Once you start your employment with the company you will be eligible,
for the Management Retention Agreement which specifies the severance benefits upon the Executives termination of employment following a Change of Control. The severance benefits indicated in the Management Retention
Agreement are as follows:



| |  |  | A lump-sum cash payment in an amount equal to fifty (50%) percent of the Executives Annual Compensation.
| | - |  | ---------------------------------------------------------------------------------------------------------



| |  |  | Fifty (50%) percent of the unvested portion of any stock option, restricted stock or other Company equity compensation held by the Executive shall
be automatically accelerated in full so as to become completely vested.
| | - |  | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------



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|Offer of Employment |  |  |  | April 15, 2009



This offer is contingent on your consent to, and results satisfactory to the Company of, reference and
background checks. Until you have been informed in writing by the Company that such checks have been completed and the results satisfactory, you should defer reliance on this offer. Enclosed please find a 2-paged document, A Summary of Your
Rights Under the Fair Credit Reporting Act, and forms for you to sign and return to us, permitting the Company, through a third party, to perform and receive the results of a background check. In addition, this offer is also contingent on your
signature agreement to the Companys Confidential Information and Invention Assignment Agreement, and your providing the Company with the proof of your identity and authorization to work in the United States, as required by federal immigration
law. The easiest method of satisfying this requirement is to provide a state drivers license and social security card, and either your passport or a copy of your birth certificate. Such documentation must be provided to us within three
(3) business days of your date of hire, or our employment relationship with you may be terminated. If you do not have these documents, please call me immediately to discuss what other documents will satisfy the requirements of this law. We have
enclosed the Employment Application and Confidential Information and Invention Assignment Agreement. If you accept this offer, please complete and sign these forms and include the required Employment Application and the Companys Confidential
Information and Invention Assignment Agreement with your acceptance. You cannot start your employment with the Company until the Companys Confidential Information and Invention Assignment Agreement has been signed and submitted with your
signed offer letter.

As a condition of your employment, you will also be required to sign and comply with an Arbitration Agreement which
requires that, in the event of any dispute or claim relating to or arising out of our employment relationship, you and the Company agree to an arbitration in which (i) you are waiving any and all rights to a jury trial but all court remedies
will be available in arbitration, (ii) we agree that all disputes between you and the Company shall be fully and finally resolved by binding arbitration, (iii) all disputes shall be resolved by a neutral arbitrator who shall issue a written
opinion, (iv) the arbitration shall provide for adequate discovery, and (v) the Company shall pay all arbitration fees with the exception of the initial filing fee, not to exceed $200.

As a full-time employee, you will be eligible to participate in the Companys full benefit package as currently and hereafter provided to other
employees, which includes: medical, dental and vision, life insurance, short and long-term disability, new hire stock options, a 401 (K) program, Flexible Spending 125, employee assistance program and tuition reimbursement. You will be entitled
to 15 days of personal paid time off during your first year of employment and 10 paid holidays in accordance with the Companys vacation/holiday policy. We have placed a great deal of emphasis on our benefits, and expect that they will continue
to evolve as we grow and as the needs of our employees and their families change.

Peter, while we anticipate that this will be a long and
rewarding relationship, you should be aware that your employment with the Company is for no specified period and constitutes at-will employment. As a result, you are free to resign at any time, for any reason or for no reason. Similarly, the Company
is free to conclude its employment relationship with you at any time, with or without cause and with or without notice. Although your job duties, title, compensation and benefits, as well as the Companys personnel policies and procedures, may
change from time-to-time, the at-will nature of your employment may only be changed in an express writing signed by you and the President of the Company.

In accepting this offer, you are representing to us that (a) you are not a party to any employment agreement or other contract or arrangement which
prohibits your full-time employment with the Company, (b) you do not know of any conflict which would restrict your employment with the Company and (c) you have not and will not bring with you to your employment with the Company any
documents, records or other confidential information belonging to former employers.

A duplicate original of this letter is enclosed for your
records. This letter, along with the agreement relating to proprietary rights between you and the Company, sets forth the terms of your employment with the Company and supersedes any prior representations or agreements, whether written or oral. This
letter may not be modified or amended except by a written agreement, signed by an officer of the Company and by you.



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|Offer of Employment |  |  |  | April 15, 2009



Peter, we are pleased that you are interested in the Company, and I believe that you will find 3PAR,
Inc. a truly exciting and fulfilling place to work. To indicate your acceptance of the Companys offer, please sign below, indicate your start date in the space provided and return this letter with the completed employment application and the
executed Confidential Information and Invention Assignment Agreement to Jeannette Robinson, VP of Human Resources no later than Friday, April 17, 2009. You can fax your acceptance by faxing the signed offer letter to
(510) 668-9595 by Friday, April 17, 2009 and later mail to my attention the original signed offer letter and completed enclosed documents. This offer is valid until this date, but should you have any questions or concerns please
call me immediately at (510) 668-9205.

We look forward to working with you at 3PAR!

Sincerely,

|                      
|----------------------
|                      
|/s/ JEANNETTE ROBINSON
|Jeannette Robinson    

Vice President Human Resources

ACCEPTED AND AGREED:



|                      |  |           |  |  |  |                                     
|--------------------- |  | --------- |  |  |  | ------------------------------------
|/s/    PETER J SLOCUM |  | 4-16-2009 |  |  |  | EXPECTED START DATE: Tuesday 4/21/09
|Peter Slocum          |  | Date      |  |  |  |                                     

Enclosures: [Duplicate Offer Letter, Employment Application, I-9 Document, an Employee Confidentiality
and Invention Assignment Agreement, A Summary of Your Rights Under the Fair Credit Reporting Act, Fair Credit Reporting Act Disclosure, and BackIs Release]