I'm investigating the possibility of setting up a multi-site cluster on Windows 2008 Server R2 / SQL Server 2008. What are some replication options I should consider? Is SAN replication the only option, or are there software options for replication?
asked
Replication options for storage in multi-site cluster
It looks like the option that we're most interested in would be storage-level mirroring. We're looking at a vendor for both a software option, and a hardware option.
One thing to beware of with SAN replication is that it does block level copies, and doesn't really have any intelligence as to what is in those blocks. If replication goes down half way through replicating a bunch of blocks, you can have a data file that's in an invalid state as far as the application using it is concerned. I have spoken to a lot of people whom this has never affected, and some whom it has. Certainly it can be mitigated with very high speed data links. If those aren't available, then for the first point of call, I would try to use SQL replication, if possible.
Edit ->
The SQL Replication I was referring to was for if the Multi-Site clustering wasn't a viable option because synchronous SAN replication couldn't be supported (for example, through lack of bandwidth). The options to look at then would be a replication scenario whereby both sites can be written, and merge replication takes care of any business rule conflicts, or where one site is read-only, in which case Database Mirroring would possibly be the answer.
This blog post is a step-by-step tutorial on how to build a two node SQL Server 2008 multi-site cluster using SteelEye DataKeeper Cluster Edition.
