Also, is it recommended to implement database mirroing without a witness instance?
Answer The witness server can run on any hardware that will run SQL Server 2005, including SQL Server 2005 Express Edition. For optimum high availability using database mirroring, a witness instance is very important, although not mandantory, assuming you want to give up some of the benefits of database mirroring. In a typical scenario of database mirroring, in which automatic failover is desired, database mirroring must be configured with the high-safety mode, which requires a witness instance running on a third server (not running on the production or mirror instances). This witness instance enables the mirror server to recognize whether to initiate an automatic failover or not. Unlike the two partners, the witness does not serve the databases being mirrored. The only purpose of the witness instance is to monitor the production and mirrored instances, determining whether or not to initiate a failover. If a witness instance is not used, then automatic failover is not available, and fa
