Achieving High Availability with SQL Server 2008
I highly recommend that you read the following whitepaper on achieving high availability with SQL Server 2008 if you are planning or currently designing a high availability solution for your SQL Server environment.
This whitepaper goes through the architecture one of our reference customers utilised to achieve 99.99% uptime of their SQL infrastructure.
High Availability and Disaster Recovery at ServiceU: A SQL Server 2008 Technical Case Study