How to implement Hyper-V replication automatic failover and load balancing of VMs with the SafeKit software (no shared disk)?

Hyper-V replication automatic failover and load balancing of VMs with SafeKit

Evidian SafeKit brings high availability to Hyper-V. This article explains how to implement quickly a Hyper-V cluster without shared disk and without specific skills. The high availabity module and a free trial are offered in the installation tab below.

Note that you can implement with the same product real-time replication and failover of other applications (database or other): see other examples of mirror modules here.

This clustering solution is recognized as the simplest to implement by our customers and partners. This solution solves only problems of hardware failures (20% of problems) including the complete failure of a computer room. If you want a complete solution that solves hardware failures (20% of problems), software failures (40% of problems) including smooth upgrade server by server and human errors (40% of problems) thanks to its simplicity, look at high availability at the application level and read this article VM HA vs Application HA.


The replication of VMs is synchronous and real-time between two Hyper-V servers. Only modifications made inside files making up a virtual machine are replicated. Note that SafeKit implements synchronous real-time replication and not the traditional Hyper-V asynchronous replication. This feature is important because with an asynchronous replication, there is data loss on a failover  as explained in this article: synchronous replication vs asynhronous replication.

When the Hyper-V server fails, there is an automatic failover of VMs on the other Hyper-V server. And when the failed server is restarted, there is an automatic reintegration of VM files without stopping them on the other active Hyper-V server.

Each VM is replicated and automatically restarted independently. Some VMs can run on the first Hyper-V server and are replicated and restarted on the second Hyper-V server. Other VMs can run on the second Hyper-V server and are replicated and restarted on the first Hyper-V server. The load balancing of VMs between the two servers are controlled by the administrator through the SafeKit web console. By clicking on a swap button, the administrator can move a VM from one Hyper-V server to the other.

The solution requires no shared disk and no special Windows configuration. Only 2 Windows servers are necessary. The SafeKit software is installed on both of them.


  • Full synchronous real-time replication of a virtual machine with failover
  • Load balancing of virtual machines between 2 Hyper-V servers with crossed replication
  • A centralized and ergonomic console to manage all VMs
  • Interesting offer for a reseller with zero integration with applications
  • In less than 10 minutes, a reseller knows how to create a Hyper-V cluster (see video)
  • Interesting for HA solutions which cannot be integrated at the application level (Active Directory, Microsoft Exchange...)
  • Interesting for applications running on unsupported OS and integrated in a Hyper-V VM replicated by SafeKit
  • The Hyper-V version that can be used with SafeKit is integrated in Windows 2012 R2 and Windows 2016

Note that this solution is limited to replication and failover of 25 VMs.

Note also that SafeKit is able to automatically re-synchronize a failed Hyper-V server without any manual operation and without stopping the VMs. It is an important differentiator when comparing SafeKit to replication solutions whose failover only works once: reintegrating the failed server in the cluster requires complex and non-automated manual operations.

Installation of a SafeKit / Hyper-V high availability cluster with synchronous replication and failover


  • you need Hyper-V installed on 2 nodes (virtual machines or physical servers)
  • on Windows, with Windows services manager, put Hyper-V services with Boot Startup Type = Manual on both nodes. SafeKit controls start of Hyper-V services in start_prim. Edit start_prim during the configuration to check if you have put all services in Manual boot including the new ones that you can add.

Package installation on Windows

  • Install the free version of SafeKit on 2 Windows nodes with Hyper-V services installed on both nodes
  • Download the Windows module
  • Put under C:\safekit\Application_Modules\demo\ (create the demo directory if it does not exist)
  • To open the Windows firewall, on both nodes start a command line as administrator, goto C:\safekit\private\bin and type  .\firewallcfg.cmd add
  • For synchronizing SafeKit at boot and at shutdown, on both nodes start a command line as administrator, goto C:\safekit\private\bin and type  .\addStartupShutdown.cmd

Go to the configuration tab

SafeKit High Availability Differentiators against Competition

SafeKit with the Hyper-V moduleMicrosoft Hyper-V Cluster & VMware HA
SafeKit with Hyper-V 2012 R2
No shared disk - synchronous real-time replication instead with no data lossShared disk and specific extenal bay of disk
Remote sites = no SAN for replicationRemote sites = replicated bays of disk across a SAN
No specific IT skill to configure the systemSpecific IT skills to configure the system
Limited number of VMs (25 VMs)Large number of VMs
VM HA with the SafeKit Hyper-V moduleApplication HA with SafeKit application modules
Application HA
Replicates too much data (App+OS)Replicates only application data
Reboot of VM on hypervisor 2 if hypervisor 1 crashes: unknown recovery time if the reboot requires manual operationQuick recovery time with restart of App on OS2 if crash of VM1
No application checker and software failoverApplication checker and software failover
Risk of downtime when fixing OS or App (single image)Smooth upgrade of OS1 or OS2 or App (two images)
Generic solution for any application / OSIntegration with high availability application modules

High availability architectures comparison

(click on the feature for more information)

FeatureSafeKit clusterOther clusters
Software clustering vs hardware clustering A software cluster with SafeKit installed on two servers
A simple software cluster with the SafeKit package just installed on two servers
Hardware clustering with external shared storage Network load balancers or dedicated proxy servers

Complex hardware clustering with external storage or network load balancers
Shared nothing vs a shared disk cluster SafeKit shared-nothing cluster: easy to deploy even in remote sites
SafeKit is a shared-nothing cluster: easy to deploy even in remote sites
Shared disk cluster: complex to deploy
A shared disk cluster is complex to deploy
Application High Availability vs Full Virtual Machine High Availability
SafeKit application HA supports hardware failure, software failure, human errors with quick recovery time
Virtual machines high availability supports only hardware failure with an unknown recovery time
Full virtual machines HA supports only hardware failure with a VM reboot and an unknown recovery time if the OS reboot does not work
Synchronous replication vs asynchronous replication
SafeKit implements real-time synchronous replication with no data loss in case of failure
Asynchronous replication with data loss on failure
With asynchronous replication, there is data loss on failure
Byte-level file replication vs block-level disk replication SafeKit cluster with byte-level file replication: simply replicates directories even in the system disk
SafeKit implements real-time byte-level file replication and is simply configured with application directories to replicate even in the system disk
Cluster with block-level disk replication: complex and require to put application data in a special disk
Block-level disk replication is complex to configure and requires to put application data in a special disk
Heartbeat, failover and quorum to avoid 2 master nodes Simple quorum in a SafeKit cluster with a split brain checker configured on a router
To avoid 2 masters, SafeKit proposes a simple split brain checker configured on a router
Complex quorum in other clusters: third machine, special quorum disk, remote hardware reset
To avoid 2 masters, other clusters require a complex configuration with a third machine, a special quorum disk, a special interconnect
Network load balancing No special network configuration in a SafeKit cluster
No dedicated server and no special network configuration are required in a SafeKit cluster for network load balancing
Special network configuration in other clusters
Special network configuration is required in other clusters for network load balancing

Customers of SafeKit High Availability Software in all Business Activities

Demonstrations of SafeKit High Availability Software

SafeKit Webinar

This webinar presents in 10 minutes Evidian SafeKit.

In this webinar, you will understand:

  • mirror and farm clusters
  • cost savings against hardware clustering solutions
  • best use cases
  • the integration process for a new application

Microsoft SQL Server Cluster

This video shows a mirror module configuration with synchronous real-time replication and failover.

The file replication and the failover are configured for Microsoft SQL Server but it works in the same manner for other databases.

Free trial here

Apache Cluster

This video shows a farm module configuration with load balancing and failover.

The load balancing and the failover are configured for Apache but it works in the same manner for other web services.

Free trial here

Hyper-V Cluster

This video shows a Hyper-V cluster with full replications of virtual machines.

Virtual machines can run on both Hyper-V servers and they are restarted in case of failure.

Free trial here

Free On-Line Training on SafeKit High Availability Software