The
key to the problem is understanding the way Microsoft words things. To
start with, there is no in-place upgrade to Exchange 2007 from a
previous version. You cannot take an Exchange 2003 system and upgrade
it to 2007. The reason for this is that Exchange 2007 didn’t run on the
64-bit platform for Server 2003, so you are required to set up a new
server with the proper 64-bit operating system. After you have the new
server, you can transition; that is, you can move your mailboxes and configuration.
You
can upgrade from Exchange 2007 RTM to SP1, as we discuss shortly. This
is the only true in-place upgrade that can be performed, but only under
specific circumstances.
However,
transitions are not for all circumstances. The only transitions you can
perform with Microsoft tools are transitions from Exchange 2000 or 2003
over to 2007. Some of the articles or books you read might use the word
upgrade when they are actually referring to a transition.
Anything other than what we’ve just described is considered a migration.
This implies a change in the messaging infrastructure. In this case,
the data, (the mailbox data), is migrated over. However, the
configuration data is not carried over as it would be in a transition.
Note
It
might surprise you to learn that Exchange 5.5 doesn’t allow for a
transition model of upgrade. Even more shocking should be the fact that
you cannot install your first Exchange 2007 server unless all Exchange
5.5 servers are removed and the Exchange mode is raised to a native
level (which indicates all Exchange 5.5 servers are out of the mix).
Note
in discussions of transitions that coexistence is unavoidable. This
refers to the time period in which your Exchange 2000/2003 servers
reside in the same organization as your Exchange 2007 server.
