X0303 4 2011-05-31 0 0001020569 IRON MOUNTAIN INC IRM 0001049128 DAUTEN KENT P KEYSTONE CAPITAL, INC. 520 LAKE COOK ROAD, SUITE 650 DEERFIELD IL 60015 1 0 0 0 Common Stock, par value, $.01 per share 2011-05-31 4 S 0 286399 34.023 D 2369862 D Common Stock, par value, $.01 per share 2011-06-01 4 S 0 269862 33.4919 D 2100000 D Common Stock, par value, $.01 per share 2011-06-01 5 G 0 E 100000 0 D 2000000 D The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $33.99 to $34.11, inclusive. The reporting person undertakes to provide to Iron Mountain Incorporated, any security holder of Iron Mountain Incorporated, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the ranges set forth in this footnote (1). The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $33.14 to $33.83, inclusive. The reporting person undertakes to provide to Iron Mountain Incorporated, any security holder of Iron Mountain Incorporated, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the ranges set forth in this footnote (2). /s/ Sarah Cammarata, under Power of Attorney dated September 16, 2010, from Kent P. Dauten 2011-06-02