While not a common necessity, I thought it would be a good idea to bring up the availability of clustering in Microsoft’s SQL Server with Singlehop. This is a technology that is available from us for both SQL Server 2005 and 2008 and is an excellent way to ensure near 100% uptime for your database back-end.
The base of something like this requires at least two dedicated servers running Windows Server 2003 or 2008 Enterprise edition, and a SAN device of some sort to store the hosted databases on. The reason the Enterprise edition of Windows is required is due to the underlying clustering software that is included with the operating system, which is not available in the Standard or Web editions. It will also require an Active Directory, which needs to be hosted on a server that is not going to be used as a node in the cluster. This machine can be Standard edition, as it will only serve as a domain controller.
After setting up the clustering service in Windows, the SQL installation can begin. It will check both servers at the same time to ensure the needed requirements are there, and it will actually install most of the database engine to the shared SAN storage. Once everything is installed, the SQL server will actually operate on a virtual ip address, which is automatically routed to the active SQL server. The SQL servers will keep in contact with each other, and if the active server stops responding, the clustering tech automatically kicks in, the san storage is brought online on the secondary server, and then SQL is fired up. Usually the transition will take no more then 5 seconds, making actual downtime nearly unnoticeable. This allows a technician to work on the server with issues without causing any problems with the databases, and makes it very easy to run things like Windows updates without worrying about downtime while the servers reboot, as you can do them one at a time.
While it may seem like a lot of servers, it is important to take these types of things into consideration when looking into SQL hosting, and hosting your entire environment as a whole. We at Singlehop feel that moving forward with a clustered MS SQL hosting platform such as this is absolutely essential to ensuring your application is always online and stable.
If this seems like something that you might need, feel free to contact your account executive with any further questions or inquiries!