How to use Hyper-V Replicas in Server 2012 R2 – Part 1

If you are running Hyper-V and you are concerned about the availability of your virtual environment, you may consider using Hyper-V Replicas. In this four-part post I will discuss using and configuring the Hyper-V Replica feature. Specifically:
1. Planning your environment for Replicas and best practices
2. How and when to use Replicas
3. Setting up Replicas with PowerShell
4. Improvements added to Replica features in Server 2012 R2
In planning and identifying your hardware resources for setting up Replicas, you do not need to purchase any special and potentially expensive storage or networking. Replicas work on any storage you are using in your virtualized environment and communicate over typical IP-based networking. You simply need to select some number of virtual machines at your primary site (where your Hyper-V host server(s) is currently located) to be replicated to your Replica site where your Replica server is located. You should size your Replica server large enough to handle future growth. One Hyper-V host can only be configured to replicate to a single Replica server, however, you can replicate to your Replica server from many (potentially geographically disperse) Hyper-V hosts. Microsoft offers a capacity planning document and tool available for download which to assist with sizing your Replica server. The tool is a wizard-based info gathering UI which collects metrics from your system:

The tool generates a log file and report containing recommendations based on the metric collection and stores them as text files in %systemdrive%UsersPublicDocumentsCapacityPlanner.

The capacity planning tool requests you to input your estimated WAN bandwidth (Mbps). You may have an existing pipe available between your primary and Replica site, but you might need to consider increasing that bandwidth based on the number and size of the VMs you wish to replicate. There are calculators available to help you determine the size of pipe you need. iCalc is one I have used on numerous times and I find it informative and straightforward. Here’s an example for calculating time/bandwidth for 5 GB of data:

One final best practice you should plan for is the initial replication process. When you turn on replica for a particular VM, the entire VM must be sent to the replica server. While you can do this over the remote network connection, I recommend using a physical device to copy the data to and then ship the device to your replica site for import.


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