<Page>
EXHIBIT 21
SCHEDULE OF SUBSIDIARIES
AS OF MARCH 9, 2004
<Table>
<Caption>
JURISDICTION OF
INCORPORATION OR NAMES UNDER WHICH THE ENTITY
ENTITY NAME ORGANIZATION DOES BUSINESS
- -------------------------------------------------------------------------------------------------------------------
Archivage Actif Groupe Iron Mountain SAS France
Archive Services Limited United Kingdom
Archivex Box Company Limited Alberta
Archivex Limited Nova Scotia
Arcus Data Security Limited United Kingdom
Britannia Data Management Limited United Kingdom
COMAC, Inc. Delaware
Custodia De Documentos LTDA Chile
Datavault Holdings Limited United Kingdom
Datavault Limited Scotland
Datavault Northwest Limited United Kingdom
Datavault Southwest Limited United Kingdom
Document and Information Management Services, Ltd. United Kingdom
DSI Technology Escrow Services, Inc. Delaware
FIME S.A. France
H. Investments Ltd. Cayman Islands
Honanross Ltd. Ireland
IMSA Peru SRL Peru
Iron Mountain Argentina Argentina
Iron Mountain Assurance Corporation Vermont
Iron Mountain Belgium NV Belgium
Iron Mountain Box Company Nova Scotia
Iron Mountain Canada Corporation Nova Scotia
Iron Mountain Cayman Ltd. Cayman Islands
Iron Mountain Chile S.A. Chile
Iron Mountain Deutschland GmbH Germany
</Table>
Page 1
<Page>
<Table>
<Caption>
JURISDICTION OF
INCORPORATION OR NAMES UNDER WHICH THE ENTITY
ENTITY NAME ORGANIZATION DOES BUSINESS
- -------------------------------------------------------------------------------------------------------------------
Iron Mountain do Brazil S.A. Brazil
Iron Mountain Espana, S.A. Spain
Iron Mountain Europe Limited United Kingdom Iron Mountain
Iron Mountain (France), S.A. France
Iron Mountain Global, Inc. Delaware
Iron Mountain Global, LLC Delaware
Iron Mountain Group (Europe) Limited United Kingdom
Iron Mountain Holdings (Europe) Limited United Kingdom
Iron Mountain Holdings (France), SNC France
Iron Mountain Iberica, SL Spain
Iron Mountain Information Management, Inc. Delaware Iron Mountain Off-Site Data Protection
Iron Mountain Records Management
Iron Mountain National Underground
Iron Mountain Digital Archives
Iron Mountain Secure Shredding
Iron Mountain Ireland Ireland
Iron Mountain Ireland (Holdings) Ireland
Iron Mountain Mexico, S.A. de R.L. de C.V. Mexico
Iron Mountain Nederland Holdings BV Netherlands
Iron Mountain (Nederland) B.V. Netherlands
Iron Mountain Norge AS Norway
Iron Mountain Norsk Grodata Senter Nowary
Iron Mountain Norge AS Norway
Iron Mountain Peru S.A. Peru
Iron Mountain Records Management (Puerto Rico), Inc. Puerto Rico Iron Mountain Records Mnagement
Iron Mountain Scotland (Holdings) Limited United Kingdom
Iron Mountain Scotland Limited United Kingdom
Iron Mountain South America Ltd. Cayman Islands
Iron Mountain Tape Technology Norge AS Norway
Iron Mountain (UK) Limited United Kingdom Iron Mountain
JAD 93 Limited United Kingdom
</Table>
Page 2
<Page>
<Table>
<Caption>
JURISDICTION OF
INCORPORATION OR NAMES UNDER WHICH THE ENTITY
ENTITY NAME ORGANIZATION DOES BUSINESS
- -------------------------------------------------------------------------------------------------------------------
Jones & Crossland Limited United Kingdom
Kestrel Data Services Limited United Kingdom
Kestrel Data UK Limited United Kingdom
Kestrel Reprographics Limited United Kingdom
Memogarde, S.A. France
Miller Data Management Limited United Kingdom
Mountain Real Estate Assets, Inc. Delaware
Mountain Reserve II, Inc. Delaware
Mountain West Palm Real Estate, Inc. Delaware Peru
Movers & Files, S.A. Peru
Pierce Leahy Europe, Limited United Kingdom
Record Data Limited Ireland
Silver Sky Jersey Channel Islands
Sistemas de Archivo Corporativo, S.A. de R.L. de C.V. Mexico
Sistemas de Archivo de Mexico, S.A. de R.L. de C.V. Mexico
Sistemas de Archivo, S.A. de R.L. de C.V. Mexico
Societe Civile Imobiliere du Chemin Cornillon France
The Document Storage Company Limited United Kingdom
397499 British Columbia Ltd. British Columbia
TM 1177 Ltd. United Kingdom
Treeline Services Corporation Delaware
Upper Providence Venture I, L.P. Pennsylvania
</Table>
Page 3