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Swiftd 
0 pts. | Feb 21 2006 9:27PM GMT
Excerpt from: <a href="http://www.petri.co.il/understanding_exhange_is.htm" title="http://www.petri.co.il/understanding_exhange_is.htm" target="_blank">http://www.petri.co.il/understanding_exh…</a>
“Exchange utilizes what Microsoft terms a single-instance message store. This single-instance message store works on a per database basis. What does this mean? If an e-mail message is sent to multiple mailboxes that are all in the same database, the message is stored once and each mailbox has a pointer to the message. The transaction is also logged in the transaction logs for the Storage Group that contains the database. However, if the e-mail message is sent to multiple mailboxes that are located in different databases, the message is copied to each database and written to the transaction logs for each Storage Group the contains the database with a copy of the message.
For example, if I send 10 users a 1MB email message and all the mailboxes are located in the same database, one copy of the message is written to the database and each mailbox points to this message which will consume 1MB of disk space in total. If the 10 recipients are located in two different databases, each database will get a copy of this message which will consume 2MB of disk space. As you can see this is a much more efficient use of space as opposed to the alternative of 10 1MB messages using up 10 MB of disk space.”
It doesn’t specifically say, but I believe that attachments are handled in the same manner. It wouldn’t be any more difficult to make a link to an attachment than it would be to a message.
Don
