X0303 4 2011-06-10 0 0001020569 IRON MOUNTAIN INC IRM 0001183339 LITTLE ARTHUR D P.O. BOX 166 HUNTRESS BRIDGE ROAD S. EFFINGHAM NH 03882 1 0 0 0 Common Stock, par value, $.01 per share 2011-06-10 4 A 0 1554 0 A 1554 D Phantom Stock 0.01 2011-06-10 4 A 0 1555 0 A Common Stock 1555 1555 D Consists of shares issuable upon the settlement of restricted stock units granted on June 10, 2011. The restricted stock units shall vest on the one year anniversary of the grant date (or, if earlier, the annual meeting of stockholders that is closest to the one year anniversary). Pursuant to Mr. Little's election to participate in the Iron Mountain Incorporated Directors Deferred Compensation Plan with respect to certain restricted stock units received on June 10, 2011, which restricted stock units shall vest on the one year anniversary of the grant date (or, if earlier, the annual meeting of stockholders that is closest to the one year anniversary), the shares of phantom stock become payable in Iron Mountain Incorporated common stock following Mr. Little's disability or cessation of service as a director. Each share of phantom stock is the economic equivalent of one share of common stock. /s/ Sarah Cammarata, under Power of Attorney dated September 16, 2010, from Arthur D. Little 2011-06-14