Quorum Drive Configuration Information (280345)

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When you install Microsoft Cluster service, you must configure storage at the hardware level so that the operating system and Cluster service have two separate physical devices for cluster usage. For example, in Disk Administrator or Disk Management, the following disks should be displayed:

• Disk 0 (usually drive C)
• Disk 1 (quorum)
• Disk 2 (data drive)

At a minimum, you must create at least one physical drive for the quorum disk and a separate physical drive for data. Each drive must be formatted as NTFS.

NTFS architecture is structured to enable file attribute indexing on a disk volume. This functionality enables the file system to efficiently locate files that match certain criteria so that sorting and searching processes function faster. However, you should not place any input/output (I/O) intensive programs on your quorum drive. Heavy input/output traffic from another source could interfere with the cluster's ability to write to the disk, which may cause the quorum resource to fail. If the quorum resource fails, the entire cluster may fail as well.

It is recommended that you configure the quorum disk size to be 500 MB; this size is the minimum required for an efficient NTFS partition. Larger disk sizes are allowable but are not currently needed. It is also recommended that you configure some form of fault tolerance at the hardware level to be used for the quorum drive, such as hardware mirroring or hardware RAID. If the quorum drive is lost, the cluster may not be available.

The quorum resource plays a crucial role in the operation of the cluster. In every cluster, a single resource is designated as the quorum resource. A quorum resource can be any resource with the following functionality:

• It offers a means of persistent arbitration. Persistent arbitration means that the quorum resource must allow a single node to gain physical control of the node and defend its control. For example, Small Computer System Interface (SCSI) disks can use Reserve and Release commands for persistent arbitration.
• It provides physical storage that can be accessed by any node in the cluster. The quorum resource stores data that is critical to recovery after there is a communication failure between cluster nodes.

Windows 2003 introduces a new quorum resource type called Majority Node Set (MNS). MNS is tailored for geographically dispersed clusters.

For additional information about MNS, click the following article number to view the article in the Microsoft Knowledge Base: NOTE: Changes in future releases of Cluster service may require a larger quorum disk size. Therefore, the recommended quorum disk size may be modified in future releases of the product.

For additional information, click the following article numbers to view the articles in the Microsoft Knowledge Base: