Failover and failback, Quorum resource, Shared storage systems – Dell PowerVault 775N (Rackmount NAS Appliance) User Manual
Page 4
Failover and Failback
If one of the cluster nodes should fail for any reason, MSCS moves (or fails over) the virtual server to another cluster node.
After the cluster node is repaired and brought online, MSCS may move (or fail back) the virtual server to the original cluster
node, if required. This failover capability enables the cluster configuration to keep network resources and application programs
running on the network while the failed node is taken offline, repaired, and brought back online. The overall impact of a node
failure to network operation is minimal.
See "
" in "
" for more information.
EMC® PowerPath®, a software component that is installed on the cluster nodes and stand-alone systems, provides an I/O
path failover solution for the I/O traffic between the host system and the storage system. Each cluster node has redundant
paths to a storage system in the cluster. If a path between the cluster nodes and the shared storage system fails for any
reason, PowerPath reroutes the Fibre Channel I/O traffic to the remaining path(s). After the failed path is repaired, PowerPath
can resume network traffic on the original path.
NOTE:
The NAS cluster solution requires EMC PowerPath.
See "
" for more information about EMC PowerPath.
Quorum Resource
In every cluster, a single disk resource is designated as the quorum resource. This resource maintains the configuration data
necessary for cluster recovery when a cluster node fails. The quorum resource contains the details of all the changes that
have been applied to a cluster database.
The quorum resource can be any resource with the following attributes:
Enables a single node to gain and defend its physical control of the quorum resource.
For example, SCSI or Fibre Channel disks use reserve and release commands for arbitration.
Provides physical storage that is accessible by any node in the cluster.
Uses the NTFS file system.
See "
" in "
" and the MSCS online documentation for more information.
NOTE:
NAS Fibre Channel clusters do not support the Majority Node Set Quorum resource type.
Shared Storage Systems
In MSCS cluster configurations, Fibre Channel provides the means for the cluster nodes to share access to one or more
external storage systems. However, only one of the cluster nodes—one of the servers in the cluster—owns any RAID volume
in the external storage system at any point in time. The Cluster Service maintains control over which node has access to each
RAID volume in the shared storage system.
See "
" for more information on Fibre Channel storage systems.
NOTE:
The Access Logix™ software is required when the storage system is connected to two or more clusters, two or
more nonclustered systems, or a combination of both clustered and nonclustered systems. Access Logix software is not
required for one stand-alone system or single cluster configurations.