Figure 8.2 Recovery-point configuration
An additional option to create an incremental VSS copy at a configurable number of
hours is also available. This gives an additional level of assurance in the integrity of
the replica at that point in time. The normal log files sent at the replication interval
provide the latest storage content, but at that point the disk may have been in an
inconsistent state on the source virtual machine. Therefore, when the replica was
started, the replica VHD might not have been in a consistent state. The incremental
VSS option, when enabled, triggers a VSS snapshot on the source prior to that cycle’s
replication, which forces the source virtual machine to ensure that the disk content is
in an application-consistent state (in the same manner as if a backup were taken, the
log file was closed and sent to the replica, and then that state was saved as the
application-consistent recovery point on the target). If the virtual machine contains an
application that has VSS writers, I suggest using the option to create an application-
consistent recovery point. The default of 4 hours is a good balance between integrity
and the additional work caused by creating a VSS recovery point on the source virtual
machine.
Once the recovery-point configuration is complete, you need to choose the method to
replicate the storage initially. It can be accomplished by any of the following:
Sending the VHD content over the network
Sending the VHD content via external media and specifying a location to export the
content
Using an existing virtual machine on the replica server as the initial copy. This can
be used if you already restored the virtual machine to the target Hyper-V server, or