Virtual Machine Migration Technologies
It is very important for an architect to select the right Hyper-V high-availability or migration technology to deploy in the production environment as MS introduced multiple choices. In addition to the Hyper-V high-availability & migration technologies that were introduced in Windows Server 2008 RTM and R2, the new Hyper-V Version 3.0 running on Windows Server 2012 Operating System comes with a bunch of new migration technologies.
Although Windows Server 2012 R2 does not introduce any new migration technologies, there have been many improvements over the existing Hyper-V versions. These technologies not only provide the high-availability of virtual machines running on a Hyper-V environment but also help reduce the IT cost. Example Shared Nothing Live migration & Hyper-v Replica which will be discussed in below section
There are five different VM migration technologies and one replication technology available depending on the operating system version i.e., Quick Migration, Live Migration, Quick Storage Migration, Storage Live Migration, Shared-Nothing Live Migration & Hyper-v Replica
Hyper-V Replication
In Windows Server 2012 the Hyper-V roleŕintroduced Hyper-V Replica as a built-in replication mechanism for virtual machines. Hyper-V Replica can asynchronously replicate a virtual machine in a primary site to a replica virtual machine in a secondary site.
Requirements
- Servers—You’ll need two servers running Windows Server 2012 or Windows Server 2012 R2 with the Hyper-V role.
- Location—servers can be physically co-located or in completely separate geographical locations.
- Topology—Primary, secondary, and extended Replica servers can be standalone or nodes in a failover cluster. A mix of standalone and clustered environments is supported.
- Certificate—. If you plan to use certificate-based authentication (required for the replicated data to be encrypted during transmission), you’ll need a certificate which can be local and self-signed, or supplied by an internal CA.
Replication
After you enable Hyper-V Replica for a specific virtual machine on the primary Hyper-V host server, initial replication begins to create an identical virtual machine in the secondary site. After the initial replication Hyper-V Replica maintains a log file for the virtual machine VHDs.
The log file is replayed in reverse order to the replica VHD in accordance with the replication frequency. This log and reverse order means that the latest changes are stored and replicated asynchronously. If replication doesn’t occur in line with the expected frequency an alert is issued.
Extended replication
Windows Server 2012 R2 introduced extended replication which allows multiple copies of data to protect from different outage scenarios. For example you might keep a second virtual machine replica in a close geographical location and a third copy more remotely.
In extended replication changes that occur on the primary virtual machines to the secondary site and to the the extended Replica server. If an outage occurs you can retrieve data from the extended replica as well as from the secondary, providing an additional layer of protection.
