Hyper-V: the simplest high availability cluster between two redundant servers without shared disk

The solution for Hyper-V

Evidian SafeKit brings high availability to Hyper-V, the free hypervisor included in all Windows versions, between two redundant servers.

This article explains how to implement quickly a Hyper-V cluster without shared disk and without specific skills.

Several virtual machines can be replicated and can run on both Windows hypervisors with crossed replication and mutual takeover.

With this solution, there is no need to configure restart scripts and define virtual IP addresses for each application.

Redundancy at the application level

In this type of solution, only application data are replicated. And only the application is restared in case of failure.

With this solution, restart scripts must be written to restart the application.

We deliver application modules to implement redundancy at the application level. They are preconfigured for well known applications and databases. You can customize them with your own services, data to replicate, application checkers. And you can combine application modules to build advanced multi-level architectures.

This solution is platform agnostic and works with applications inside physical machines, virtual machines, in the Cloud. Any hypervisor is supported (VMware, Hyper-V...).

Solution for a new application (restart scripts to write): Windows, Linux

Redundancy at the virtual machine level

In this type of solution, the full Virtual Machine (VM) is replicated (Application + OS). And the full VM is restarted in case of failure.

The advantage is that there is no restart scripts to write per application and no virtual IP address to define. If you do not know how the application works, this is the best solution.

This solution works with Windows/Hyper-V and Linux/KVM but not with VMware. This is an active/active solution with several virtual machines replicated and restarted between two nodes.

Solution for a new application (no restart script to write): Windows/Hyper-V, Linux/KVM

SafeKit quick installation guide with the Hyper-V module

Step by step configuration

1. Prerequisites

The VM1 virtual machine files (VM1 configuration file, virtual hard disk...) must be put in a same folder: this folder will be replicated by SafeKit.

Make sure the virtual switch name(s) referenced by the virtual machine exist on both Hyper-V servers and corresponds to the same physical network.

If all the files of VM1 are not in the same folder, use Hyper-V manager:

Export VM1 in a folder, for example in D:\Repli-Hyper-V
This export will create a folder D:\Repli-Hyper-V\VM1\ containing all VM1 files
Remove VM1 from the inventory of Hyper-V manager
Import VM1, previously exported, into Hyper-V manager

5. Configure the module

Choose an automatic start of the module at boot without delay.
Normally, you have a single heartbeat network on which the replication is made. But, you can define a private network if necessary.
Put in VM_PATH, the root path of the replicated directory (D:\Repli-Hyper-V).
Enter in VM_NAME, the name of the virtual machine (VM1).

We assume that all VM1 files are in D:\Repli-Hyper-V\VM1\ (see prerequisites). This directory will be replicated in real-time by SafeKit.

The NORMAL_STOP and FORCE_STOP values can be "stop", "save" or "off":

"stop" shutdowns the VM when the module is stopped.
"save" saves the current state of the VM (suspend) when the module is stopped.
"off" turns off the VM (power off) when the module is stopped.

"stop" is recommended because it causes the shutdown then the reboot of the VM when the module is stopped and restarted. Thus the application inside the VM is restarted.

This will be the case, for example, when switching between primary and secondary roles.

This operation will report the configuration in the userconfig.xml file on both nodes (more information in the training with the command line).

8. Wait for the transition to ALONE (green)

Node 1 should reach the ALONE (green) state, which means that the start_prim script has been executed on node 1.

If the status is ALONE (green) and VM1 is not started, check output messages of start_prim in the Application Log of node 1.

If node 1 does not reach ALONE (green) state, analyze why with the Module Log of node 1.

If the cluster is in WAIT (red) not uptodate - STOP (red) not uptodate state, stop the WAIT node and force its start as primary.

12. Testing

Stop the PRIM node by scrolling down its contextual menu and clicking Stop.
Verify that there is a failover on the SECOND node which should become ALONE (green).
Check the restart of VM1 with Hyper-V manager.

If VM1 is not started on node 2 while the state is ALONE (green), check the output messages of the start_prim script in the Application Log of node 2.

As the start_prim script imports the virtual machine on node 2, the failover can fail because of Hyper-V settings (see this article).

If ALONE (green) is not reached, analyze why with the Module Log of node 2.

More information on tests in the User's Guide

Learn more

Demonstration

Advanced clustering architectures

Several modules can be deployed on the same cluster. Thus, advanced clustering architectures can be implemented:

the farm+mirror cluster built by deploying a farm module and a mirror module on the same cluster,
the active/active cluster with replication built by deploying several mirror modules on 2 servers,
the Hyper-V cluster or KVM cluster with real-time replication and failover of full virtual machines between 2 active hypervisors,
the N-1 cluster built by deploying N mirror modules on N+1 servers.

Key differentiators of SafeKit vs Microsoft Hyper-V cluster and VMware HA

Key differentiators of high availability at the virtual machine level or at the application level

Key differentiators of the SafeKit high availability technology

Software clustering vs hardware clustering More info >
A simple software cluster with the SafeKit package just installed on two servers	Complex hardware clustering with external storage or network load balancers
Shared nothing vs a shared disk cluster More info >
SafeKit is a shared-nothing cluster: easy to deploy even in remote sites	A shared disk cluster is complex to deploy
Application High Availability vs Full Virtual Machine High Availability More info >
Application HA supports hardware failure and software failure with a quick recovery time (RTO around 1 mn or less). Application HA requires to define restart scripts per application and folders to replicate (SafeKit application modules).	Full virtual machines HA supports only hardware failure with a VM reboot and a recovery time depending on the OS reboot. No restart scripts to define with full virtual machines HA (SafeKit hyperv.safe or kvm.safe modules). Hypervisors are active/active with just multiple virtual machines.
High availability vs fault tolerance More info >
No dedicated server with SafeKit. Each server can be the failover server of the other one.Software failure with restart in another OS environment. Smooth upgrade of application and OS possible server by server (version N and N+1 can coexist)	Secondary server dedicated to the execution of the same application synchronized at the instruction level.Software exception on both servers at the same time. Smooth upgrade not possible
Synchronous replication vs asynchronous replication More info >
SafeKit implements real-time synchronous replication with no data loss in case of failure	With asynchronous replication, there is data loss on failure
Byte-level file replication vs block-level disk replication More info >
SafeKit implements real-time byte-level file replication and is simply configured with application directories to replicate even in the system 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 More info >
To avoid 2 masters, SafeKit proposes a simple split brain checker configured on a router	To avoid 2 masters, other clusters require a complex configuration with a third machine, a special quorum disk, a special interconnect
Virtual IP address primary/secondary, network load balancing, failover More info >
No dedicated proxy servers and no special network configuration are required in a SafeKit cluster for virtual IP addresses	Special network configuration is required in other clusters for virtual IP addresses. Note that SafeKit offers a health check adapted to load balancers

Network load balancing and failover
Windows farm	Linux farm
Generic Windows farm >	Generic Linux farm >
Microsoft IIS >	-
NGINX >
Apache >
Amazon AWS farm >
Microsoft Azure farm >
Google GCP farm >
Other cloud >

Real-time file replication and failover
Windows mirror	Linux mirror
Generic Windows mirror >	Generic Linux mirror >
Microsoft SQL Server >	-
Oracle >
MariaDB >
MySQL >
PostgreSQL >
Firebird >
Windows Hyper-V >	-
-	Linux KVM >
-	Docker >
-	Kubernetes >
-	Elasticsearch >
Milestone XProtect >	-
Genetec SQL Server >	-
Hanwha Wisenet Wave > Hanwha Wisenet SSM >	-
Nedap AEOS >	-
Siemens SIMATIC WinCC > Siemens SIMATIC PCS 7 > Siemens Siveillance > Siemens Desigo CC > Siemens SiPass > Siemens SIPORT >	-
Bosch AMS > Bosch BIS > Bosch BVMS >	-
Amazon AWS mirror >
Microsoft Azure mirror >
Google GCP mirror >
Other cloud >

SafeKit with the Hyper-V module or the KVM module	Microsoft Hyper-V Cluster & VMware HA

No shared disk - synchronous real-time replication instead with no data loss	Shared disk and specific extenal bay of disk
Remote sites = no SAN for replication	Remote sites = replicated bays of disk across a SAN
No specific IT skill to configure the system	Specific IT skills to configure the system

VM HA with the SafeKit Hyper-V or KVM module	Application HA with SafeKit application modules
SafeKit inside 2 hypervisors SafeKit replication and failover of full VM	SafeKit inside 2 virtual or physical machines SafeKit replication and failover at application level
Replicates more data (App+OS)	Replicates only application data
Reboot of VM on hypervisor 2 if hypervisor 1 crashes Recovery time depending on the OS reboot	Quick recovery time with restart of App on OS2 if crash of server 1 Around 1 mn or less (see RTO/RPO here) Application checker and software failover
Generic solution for any application / OS	Restart scripts to be written in application modules

Hyper-V: the simplest high availability cluster between two redundant servers without shared disk

Evidian SafeKit - synchronous replication, automatic failover and load balancing of virtual machines

How to implement a Hyper-V cluster with the SafeKit software between two redundant servers without shared disk?

Replication and failover of virtual machines (VM)

The solution for Hyper-V

A generic product

Partners, the success with SafeKit

Building Management Software (BMS)

Video Management Software (VMS)

Electronic Access Control Software (EACS)

SCADA Software (Industry)

How the SafeKit Hyper-V cluster works?

Step 1. Real-time replication

Step 2. Automatic failover

Step 3. Automatic failback

Step 4. Back to normal

Choose between redundancy at the application level or at the virtual machine level

Redundancy at the application level

Redundancy at the virtual machine level

Typical usage with SafeKit

Why a replication of a few Tera-bytes?

Why a replication < 1,000,000 files?

Why a failover < 25 replicated VMs?

Why a LAN/VLAN network between remote sites?

SafeKit free trial + Hyper-V mirror module + quick installation guide

Prerequisites

Package installation on Windows

Module installation on Windows

1. Prerequisites

2. Launch the SafeKit console

3. Configure node addresses

4. Choose the module

5. Configure the module

6. Verify successful configuration

7. Start the node with up-to-date data

8. Wait for the transition to ALONE (green)

9. Start node 2

10. Verify that the cluster is operational

11. Remove the start of VM1 in Hyper-V at boot

12. Testing

Module log

Application log

Advanced configuration

Support

Demonstration of a Hyper-V cluster with Evidian SafeKit between two redundant servers

SafeKit Modules for Plug&Play Redundancy and High Availability Solutions

Network load balancing and failover

Advanced clustering architectures

Real-time file replication and failover

Demonstrations of Redundancy and High Availability Solutions

SafeKit Webinar

Microsoft SQL Server Cluster

Apache Cluster

Hyper-V Cluster

SafeKit Customers in all Business Activities

Best use cases [+]

Video management, access control, building management [+]

TV broadcasting [+]

Finance [+]

Industry [+]

Air traffic control [+]

Bank [+]

Transport [+]

Healthcare [+]

Government [+]

Redundancy and High Availability Differentiators against Competition

SafeKit Technical Documentation

User's Guide

Application Modules

Release Notes

Presales documentation

SafeKit Training

Introduction

Installation, Console, CLI

Advanced configuration

Support