what are Quorum disk

[vmwaredude1]

Folks,

Can you please tell me what are quorum disks ? I am referring to - Setup for MS Cluster Service.

Thanks

[RParker]

Quorum Disk (qdisk) contains the cluster state and timestamp information. It also allows continuous cluster operation without user intervention by configuring arbitrary heuristics which provides each cluster member flexibility in handling network-partition ("split-brain scenario") failure or when majority of the cluster members fails.

Q. What is the quorum used for?

A. Server clusters require a quorum resource to function. The quorum resource, like any other resource, is a resource which can only be owned by one server at a time, and for which servers can negotiate for ownership. Negotiating for the quorum resource allows Server clusters to avoid "split-brain" situations where the servers are active and think the other servers are down. This can happen when, for example, the cluster interconnect is lost and network response time is problematic. The quorum resource is used to store the definitive copy of the cluster configuration so that regardless of any sequence of failures, the cluster configuration will always remain consistent.

Q. What options do I have for my quorum resource?

A. In Windows 2000, there are two quorum-capable resources:

•	Physical Disk Resource This allows a disk on the shared cluster storage bus to be used as the quorum resource. The cluster code uses SCSI commands to arbitrate for the quorum disk ensuring only one node owns the quorum disk at any point in time. This is the standard quorum resource that Microsoft recommends for all production Windows 2000 clusters.	Note:
Some storage vendors provide their own quorum capable resources for specific hardware solutions (e.g., IBM Shark Storage) or software solutions (such as Veritas Volume Manager). You should use these if they are required for your environment.

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Local Quorum

This quorum-capable resource allows a single node cluster to be setup without having a second storage bus. This type of cluster is useful for developing cluster-aware software without having to have a multi-node cluster.Local Quorum can be used in a production environment if you want to take advantage of the resource health monitoring and local restart facilities provided by Server cluster on a single node.

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In Windows Server 2003 we have introduced another quorum capable resource type

[Schorschi · Accepted solution]

What IS a Qurom disk is more to the point, meaning that it is a single instance per a given cluster. It holds common meta-data that allows all nodes in a given cluster to understand how they relate to each other. Key to this meta-data is the cluster log. A quorum disk must be on shared storage common to all notes, but must be separate and isolated from all other shared storage for the cluster.