Exchange 2003 Databases and the Exchange store

Another Exchange posting. Here only because postnuke doesn’t like all the html in the post.

I’m playing around, trying to tweak Exchange 2003 to get the best possible performance in my Virtual machine demo environment so that my demos look good, and I’ve been reading the Optimising Storage document on TechNet.   There’s a table in this document which talks about the stored and their impact on disk I/O which I thought was worth reproducing here.  I tend to get asked for this quite a lot so here it is…

Table 2   Exchange store components and corresponding impact to disk I/O


Component Why it impacts disk I/O

Jet database (.edb file)

The Jet database is used to store all data submitted from MAPI clients. All client activity generated by a MAPI client causes updates to the Jet database.


Streaming database (.stm file)


Stores attachments and data submitted from IMAP4, NNTP, Microsoft Outlook® Web Access, or SMTP. Pointers are saved in the Jet database so the data can be delivered to MAPI clients upon request.

Stores incoming SMTP mail. If the data contains MAPI information, the SMTP message is then transferred to the Jet database.

All internet protocol client activity causes updates to the streaming database.


Transaction log files (.log files)


All changes made to the database are first committed to transaction log files. This means that any time a user sends or reads a message, and any time a user modifies data stored in their mailbox, that change is written to the transaction log file. The change is immediately committed to the in-RAM database cache, and then copied back to disk when the system’s load permits. Transactions are also read back when a database is mounted.

[Via Eileen Brown’s WebLog]

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