Thursday, 28 January 2010

Extensible Storage Engine (ESE) explained

Extensible Storage Engine (ESE)

The core storage technology of Microsoft Exchange Server and Active Directory is called Exchange Extensible Storage Engine (ESE), also known as JET Blue. It is an Indexed Sequential Access Method (ISAM) data storage technology whose purpose is to allow applications to store and retrieve data via indexed and sequential access. Window Mail and Desktop Search in the Windows Vista operating system also makes use of ESE to store indexes and property information respectively.

To highlight basic features of ESE –

  • Microsoft JET is an advanced 32-bit multithreaded database engine that combines speed and performance with other advanced features to enhance transaction-based processing capabilities.
  • A crash recovery mechanism is provided so that data consistency is maintained even in the event of a system crash.
  • Transactions in ESE are highly concurrent, making ESE suitable for server applications. ESE caches data intelligently to ensure high performance access to data.
  • In addition, ESE is lightweight making, optimized for fast data storage and retrieval.

The ESE Runtime (ESENT.DLL) has shipped in every Windows release since Windows 2000, with the native x64 version of the ESE runtime shipping with x64 versions of Windows XP and Windows Server 2003. The 64 bit edition support started with Exchange 2007; up to Exchange 2003, ESE runtime was shipped with only the 32 bit edition.

Exchange Information Store

The information store, which is the key component for database management in Exchange Server, is actually two separate databases. The private information store database, Priv.edb, manages data in user mailboxes. The public information store, Pub.edb, manages data in public folders.

Private store consist of .edb and .stm files. The .edb file is the main repository for the mailbox data. The .edb file is accessed by ESE directly. The fundamental construct of the .edb file is the b-tree structure. The ESE 4 KB pages are arranged into tables that form a large database file containing Exchange data.

The .stm or streaming media file is used in conjunction with the .edb file to comprise the Exchange database. Both files together make up the database, and as such, they should always be treated as a single entity.
The information store works with the Messaging Application Programming Interface (MAPI) and the database engine to ensure that all user actions are recorded on the server's hard disk.

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