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An Overview of Hyper-V Live Migration

16 bytes added, 18:20, 23 September 2009
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In the previous chapter we looked at the the migration of Hyper-V virtual machines using a technique that required the virtual machine to be powered off or placed into a saved state. The downside to this approach is that it is a manual process and any service provided by the virtual machine is interrupted during the migration process, hardly an acceptable solution in mission critical and enterprise level environments.
Fortunately Hyper-V 2008 R2 introduced a feature called ''Live Migration'' whereby a running virtual machine can be migrated from one host system to another with no interruption in service.
== Hyper-V Live Migration Configuration Requirements ==
Before a running virtual machine can be migrated from one host to another there are some mandatory requirements thant that must first be met:
* Hyper-V 2008 R2 must be deployed on both hosts. The first version of Hyper-V does not support live migration.
* The virtual machine's ''Automatic Start Action'' setting must be set to do ''Nothing''.
* All Hyper-V hosts in the Failover cluster must be configured to boot from the same drive letter. In other words, a host that boots from the C drive cannot perform a live migration to a host that boots from the D drive.
== The Live Migration Process ==
* '''Configuration transfer''' - The source host transfers the configuration data for the virtual machine to the destination host.
* '''Destination VM creation''' - Based on the configuration data the destination host creates a new virtual machine and allocated allocates adequate memory.
* '''Transfer of memory pages''' - The memeory pages used by the virtual machine on the source host are transferred to the destination host. During this process, the source host monitors the memory and records any changes that take place after each page is transferred. Modified pages are then resent to the destination host.
For a command-line or script based method of performing live migrations, the Windows PowerShell environment may be used as follows:
To open a PowerShell window, select ''Start -> All Programs -> Accessories -> Windows Powershell -> Windows PowerShell''. Within the PowerShell window, install the Failover Clustering feature as followfollows:

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