The illustration that follows shows a typical Microsoft failover cluster with a campus cluster setup of disks. For campus clusters, each disk group must contain an equal number of disks on each site. This example has only one application disk group that spans the storage arrays at both sites.

The data and database log on Site A are mirrored to Site B. Each mirrored volume can have more than two disks, but must have an even number, such as four. All the application data could be in one large mirrored volume with multiple disks, but the same number of disks are required on both sites for the mirroring. It is recommended that the log volumes be on separate disks from the data.

In the example, a four-way mirror for the quorum volume provides additional redundancy. The minimum configuration would be a two-way mirror. If possible, use small disks for the quorum volume. Microsoft recommends 500 MB for the quorum volume.