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How does Exchange store file attachments?

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Michael Hering

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Jul 26, 2007, 2:06:02 PM7/26/07
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Hello everyone,

I have what I hope is a pretty simple question, which deals with how
Exchange handles attachements.

If an Exchange user sends an attachment to say ten (10) different Exchange
users how does the serve handle this request? Does it duplicate a single file
ten (10) times and deposit a copy in each users mailbox? Does it create a
single instance of the attachment and link the ten (10) mailboxs to the
single attachment instance?

Thank you for your assistance in this matter.

: Michael

Mark Arnold [MVP]

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Jul 26, 2007, 2:11:53 PM7/26/07
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It does the latter.
Do a search for "Single Instance Storage" if you want to fully
understand the process.

Michael Hering

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Jul 26, 2007, 2:24:03 PM7/26/07
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Mark,

Thank you for your assitance!

: Michael

John Fullbright

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Jul 26, 2007, 6:00:03 PM7/26/07
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It depends.

Let's say you have one exchange server and all 10 users are on the same
server using mapi clients to access mail. One copy is stored in the edb
file, and all 11 mailboxes have a pointer to it in the message table and
attachment table (the first mailbox's sent items and the 10 recipients'
inboxes.

Let say the sending user uses pop or imap or webdav to connect to exchange,
and the 10 recipients use mapi clients. The attachment will be stored in
both the stm and edb files.

Let's say all users are on the same exchange server and the sending user
and 9 of the recipients use MAPI and oune recipient uses OWA. Result, the
attachment is stored in the edb file and the stm file.

Lets sall all users are using pop/imap/webdav. The attachment is stored in
the stm file.

It gets even more complicated if you add multiple exchange servers or
messages that are received from the internet. Depending on how it arrived,
a message is either stored in the stm or edb, or in the stm and some
properties are promoted to the edb.. SIS depends on the store/server on
which the sending and receiving users are located.

"Michael Hering" <Michae...@discussions.microsoft.com> wrote in message
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Michael Hering

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Jul 26, 2007, 6:28:01 PM7/26/07
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John,

Thank you for the info!

: Michael

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