I remember it used to be the best practice for placing the Exchange servers to its own site in Exchange 2003. To protect the DC/GC and dedicate them exchange usage only, and not letting other processes to eat up all DC/GC resources in multimaster replication model, we even lift the "DC locator DNs SRV Records" and give higher priority so that those DC/GC should be used by exchange only.
The problem is hard coding "DSAccess" causes the single point of failure if dedicated DC's are not accessible. Putting Exchange to its own site, will force exchange (DSAccess) to located DC's within its site fist, and it they are no accessible they will go out and located other DC's so that exchange remains happy and functionally.
Placing DC/GC ratio is 1:4, meaning 1 DC/GC per 4 Exchange servers, for Exchange 2007 1 DC/GC for per mailbox server. (Details in the following article)
How do all these apply to Exchange 2007? If you remember the changes in Exchange 2007 structure, "Site base routing" you will make you, predict a close guess and know dedicated DC/GC is not recommended for Exchange 2007.
I always wondered why we could not have more control over DSaccess, such as hard code it for specific server and at the same time being able to say, if these wont response go discover automatically any available GC or even tell it where to go second? Maybe next version of exchange (-:, who knows
Oz ozugurlu MVP (Exchange)
MCITP (EMA) , MCITP (EA ) MCITP(SA),
MCSE (M+,S+) MCDST, Security+, Server +,Project+