A SQL Server failover cluster is just one of a number of supported high availability schemes for your protel implementation. This article is a general introduction to the subject.
The problem with a single instance, single server installation
When the protel database is built on a single, default instance of SQL Server, there is no redundancies should the server be taken offline for any reason. A single instance means a single installation of SQL server on a single operating system on a single server.
If you have to apply a service pack or security patches to the server (you will), best practice demands the server be rebooted immediately following an update. A reboot means the database will be unavailable to the protel user community for the duration of the maintenance window. Scheduling may be possible, but it might also present certain challenges if the user community is spread across multiple timezones.
Unplanned hardware or operating system failures will also take the database offline. Motherboards die and drivers fail. Wouldn't it be nice if our protel instance wasn't tied to a particular server or a particular operating system? Enter failover clustering.
SQL Server failover clustering