Because of the architecture of CSV, there is improved cluster node connectivity fault tolerance that directly affects VMs running on the cluster. The CSV architecture implements a mechanism, known as dynamic I/O redirection, where I/O can be rerouted within the failover cluster based on connection availability, as illustrated in the following figure.
Figure 5: Dynamic IO redirection for Cluster Shared Volumes
The first type of failure that can be redirected is the failure of a cluster node connection to the shared storage between cluster nodes, typically on a Storage Area Network (SAN). As shown in the following figure, if the SAN connection on Node 2 fails, the I/O operations are redirected over the network to Node 1. Node 1 then performs the I/O operation to the SAN. This allows you do a Live Migration of the VM running on Node 2 to Node 1.
Figure 6: IO connectivity fault tolerance for CSV
The next type of failure that can be redirected is the failure of network connectivity for a cluster node. As shown in the following figure, the primary network connection between Node 1 and Node 2 fails. Node 2 automatically reroutes network traffic over a redundant network connection and Node 1 performs the network I/O.
Figure 7: Network fault tolerance for CSV
The next type of failure that can be redirected is the failure of an entire cluster node. As shown in the following figure, Node 1 has ownership of a volume that is used by the VM running on Node 2. In the event of a complete failure of Node 1, ownership of the volume is changed to Node 2 without any interruption of service to the VM running on Node 2.
Figure 8: Node fault tolerance for CSV
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