Further to my previous blog on SharePoint Disaster recovery (Cross Datacenter Failover with SQL 2005 and MOSS 2007), there is further consideration as to which version of SQL 2005 you choose for the mirroring. SQL 2005 Standard supports Synchronous / SAFETY=FULL configuration while SQL 2005 Enterprise supports Asynchronous mirroring. What this means is that with SQL 2005 Std the transaction does not commit on production until it commits on the secondary (mirrored data server). If you have a slow LAN o WAN, this is less preferred UNLESS you absolutely need 100% of all data mirrored no matter what. This is where the SAFETY=FULL comes in. Full Safety means every transaction is guaranteed to be writing. SQL 2005 Enterprise Asynchronous mode does not support SAFETY=FULL.
General Guidelines to consider are:
If you need speed at any cost, choose asynchronous.
If you need data integrity, choose synchronous.
I am currently working on a deployment that has mirroring planned across Europe to North America . Once I have some numbers to provide to provide real world feasibility of this type of mirroring strategy, I will post them to this site.