I am looking to upgrade our Exchange 2007 environment to Exchange 2010 and with having to install new servers I'm reviewing the design of the existing environment which comprises of two exchange servers... one for CAS and one for mailbox both on local SAN storage (virtualised) ...
The company has around 500 email users (small / medium business) with around 80% using Outlook web access. We also now have domain controllers across two sites (two in each) with a private/leased line between them.
I'm looking at providing high availability using DAG's but wondered if anyone could recommend a solution with regards to where to place the exchange servers, how many CAS, mailbox, hub, etc roles to consider?
Any advice appreciated!