Dell PowerVault 775N (Rackmount NAS Appliance) - Manual (Page 75)

Table 7-1. Node States and Definitions
State Definition
Down The node is not actively participating in cluster operations.
Joining The node is in the process of becoming an active participant in the cluster operations.
Paused The node is actively participating in cluster operations but cannot take ownership of resource groups and cannot
bring resources online.
Up The node is actively participating in all cluster operations, including hosting cluster groups.
Unknown The state cannot be determined.
When the Cluster Service is configured for the first time on a node, the administrator must choose whether that node forms
its own cluster or joins an existing cluster. When the Cluster Service is started on a node, that node searches for other active
nodes on networks enabled for internal cluster communications.
Forming a New Cluster
If a cluster cannot be joined, the node attempts to form the cluster by gaining control of the quorum resource. If the node
gains control of the quorum resource, the node forms the cluster and uses the recovery logs in the quorum resource to
update its cluster database. The Cluster Service maintains a consistent, updated copy of the cluster database on all active
nodes.
Joining an Existing Cluster
A node can join an existing cluster if it can communicate with another cluster node. If a cluster exists and the joining node
finds an active node, it attempts to join that node's cluster. If it succeeds, the Cluster Service then validates the node's name
and verifies version compatibility. If the validation process succeeds, the node joins the cluster. The node is updated with the
latest copy of the cluster database.
Groups
A group is a collection of cluster resources with the following characteristics:
All of the resources in the group are moved to the alternate node when one resource in a group fails and it is necessary
to move the resource to an alternate node.
A group is always owned by one node at any point in time, and a resource is always a member of a single group.
Therefore, all of a group's resources reside on the same node.
Groups enable resources to be combined into larger logical units. Typically a group is made up of related or dependent
resources, such as applications and their associated peripherals and data. However, groups can also be established with
resources that are unrelated and nondependent to balance the load or for administrative convenience.
Every group maintains a prioritized list of the nodes that can and should act as its host. The preferred nodes list is generated
by the Cluster Service. Cluster Service produces a list of preferred nodes for a group from the list of possible owners that is
maintained by the group's resources and can be modified by an Administrator.
To maximize the processing power of a cluster, establish at least as many groups as there are nodes in the cluster.