Users Guide

18 Clustering Implementations for High Availability
Figure 2-7. Hyper-V Host Cluster after One Server Fails
Unlike in the case of a planned failover where the administrator chooses a
specific destination node for the VMs, in an unplanned scenario the cluster
service will choose the appropriate destination server to move the VMs to. If a
specific cluster node is found to not have sufficient resources such as CPU or
memory to host the VMs, the cluster service will attempt to start the VM on
another available node in the cluster.
NOTE: Using the advanced features available in Windows Failover Clustering,
rules may be set to restrict certain VMs to only run on certain nodes of a Hyper-V
Host Cluster. For more information, refer to "Administering High Availability for
Hyper-V" on page 45.
NOTE: Because the state of the VM is not retained during an unplanned failover,
the processors (and their features) on the originating and destination nodes do not
have to match. However, Dell strongly recommends that all servers in a Hyper-V
Host Cluster have identical hardware to ensure that it also supports planned
migrations.