Exhibit 99.1

JOINT FILING AGREEMENT

In accordance with Rule 13d-1(k)(1)(iii) under the Securities Exchange Act of 1934, as amended, the persons named below agree to the joint filing on behalf of each of them of a Statement on Schedule 13D (including additional amendments thereto) with respect to the shares of Common Stock, $0.01 par value per share, of Commvault Systems, Inc. This Joint Filing Agreement shall be filed as an Exhibit to such Statement.

Dated: March 30, 2020

STARBOARD VALUE AND OPPORTUNITY MASTER FUND LTD By: Starboard Value LP, its investment manager   Starboard Value and Opportunity S LLC By: Starboard Value LP, its manager Starboard Value and Opportunity C LP By: Starboard Value R LP, its general partner   STARBOARD VALUE R LP By: Starboard Value R GP LLC, its general partner   Starboard Value and Opportunity Master Fund L LP By: Starboard Value L LP, its general partner     Starboard Value L LP By: Starboard Value R GP LLC, its general partner   STARBOARD VALUE LP By: Starboard Value GP LLC, its general partner   STARBOARD VALUE GP LLC By: Starboard Principal Co LP, its member   STARBOARD PRINCIPAL CO LP By: Starboard Principal Co GP LLC, its general partner   STARBOARD PRINCIPAL CO GP LLC   Starboard Value R GP LLC

By:	/s/ Jeffrey C. Smith
	Name:	Jeffrey C. Smith
	Title:	Authorized Signatory

/s/ Jeffrey C. Smith

Jeffrey C. Smith

Individually and as attorney-in-fact for Peter A. Feld