Users Guide

Clustering Implementations for High Availability 15
Figure 2-5. Hyper-V Host Cluster after Migrating
This save and restore operation ensures that the state of the VM is retained
during the migration process. The guest operating system is unaware of this
VM save and restore process: the guest OS is "frozen" during the migration
period. Microsoft calls this capability to migrate VMs across physical servers
"Quick Migration".
Even though there is no loss of state or data during this process, it is not a
"Live" migration process. The guest OS and the workloads within the VM will
be offline and not available to users during the migration period.
NOTE: Any active connections with the guest operating system in the VMs will be
lost when the VM undergoes migration. The connections have to be re-established
after the migration is complete.
The offline duration period is typically between 15 seconds and a few
minutes, depending mainly on the following factors:
• Amount of memory used by the guest operating system: This is the most
important factor because the time taken for VM migration is directly
proportional to the amount of memory that is being used by the guest
operating system. The more memory that is being used by the guest OS at
the time of the migration, the longer the migration time. Note that the