Exchange 2010 DAG

So we're in the planning phase of a migration from Exchange 2003 to Exchange 2010.. right now I'm googling results to use a sales points to upper management which bring me to this DAG question:  I have two locations, MS and MI.  If I have a server in both locations and both are functioning as Mailbox/Client Access and Hub roles will each house mailboxes for the other so that in the event one server goes down clients from both locations will still be able to access their mailboxes?

Shorter version: If MS goes down, will MS clients be able to access their mailboxes hosted from MI?
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Ben HartAsked:
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Glen KnightCommented:
I would recommend seperating the roles so you have a mailbox server at each location and a CAS & HT Server at each location.

You could then use DAG on the mailbox roles and create a CAS Array between the CAS Servers.
Please see my article here on DAG:
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Ben HartAuthor Commented:
I had just literally read about that method.. however in our case (not being a large scale company) that more perfect server scenario is out of reach financially.
Ben HartAuthor Commented:
Sorry meant to add this to the above reply.. So being that we;'d have two CA's, two Mailboxes and two hubs (all on two physical servers).. would the end user's client seamlessly rollover to the working server?
BusbarSolutions ArchitectCommented:
Hi Ubadmin,
to add to demazter:
for DAG point of view the selling points other than HA, is providing HA with very cheap storage, HA in DAG doesn't requires SAN or even fast storage, Exchange 2010 can be running fine on 10K Harddisks with no issues which gives the company the HA with very cheap capability.

the other option is the HA on the database level, so you can failover at the database level no the server level which gives you greater flexibility
for the HA between the sites, users will still connect to the CAS server not the mailbox server, so if the mailbox server or the DB fails the users will connect to the mailbox in the other site, but you need to plan for total site disaster recovery which is site resiliencey, you have also to consider DAC:
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