KVM: the simplest high availability cluster with real-time replication, automatic failover and load balancing of VMs between two redundant servers without shared disk

Evidian SafeKit

How to implement a Linux KVM cluster with replication, automatic failover and load balancing of VMs and with the SafeKit software between two redundant servers without shared disk?

A Linux KVM cluster with SafeKit: real-time replication, load balancing and failover between two redundant servers

Evidian SafeKit brings high availability to KVM between two redundant servers. This article explains how to implement quickly a KVM cluster without shared disk and without specific skills. The high availabity module kvm.safe and a free trial are offered in the Installation tab below.

Note that SafeKit is a generic product. You can implement with the same product real-time replication and failover of new directories and services, databases, docker containers, full Hyper-V or KVM virtual machines, Cloud applications. 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

  • hardware failures (20% of problems), including the complete failure of a computer room,
  • and human errors (40% of problems) thanks to its ease of use, including a very simple administration web console to configure, control and monitor clusters,
  • but it does not solve software failures (40% of problems), including smooth upgrade server by server,
  • and the recovery time in case of failure depends on the time to reboot VMs.

For a complete solution with quick recovery time, consider high availability at the application level and read this article VM HA vs Application HA.

Note that the solution presented here allows replication and failover at the virtual machine level. But SafeKit also offers a solution with replication and failover at the container level (Docker).

Principle

The replication of VMs is synchronous and real-time between two KVM 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 KVM 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 KVM server fails, there is an automatic failover of VMs on the other KVM server. And when the failed server is restarted, there is an automatic reintegration of VM files without stopping them on the other active KVM server.

Each VM is replicated and automatically restarted independently. Some VMs can run on the first KVM server and are replicated and restarted on the second KVM server. Other VMs can run on the second KVM server and are replicated and restarted on the first KVM 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 KVM server to the other.

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

Features

  • No shared disk
  • Synchronous real-time replication of a virtual machine with failover
  • Very simple solution to implement
  • Load balancing of several virtual machines between 2 KVM servers with crossed replication
  • A centralized and ergonomic console to manage all VMs
  • Interesting offer for a reseller with zero integration with applications
  • Interesting for HA solutions which cannot be integrated at the application level (application + OS in a virtual machine replicated by SafeKit)
  • Simple solution for HA of a Kubernetes application on premise: put Minikube + containers + etcd database + OS in a VM replicated by SafeKit; no need to install a Kubernetes cluster on premise
  • Interesting for applications running on unsupported OS and integrated in a KVM VM replicated by SafeKit

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 KVM 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.

Free trial + kvm.safe module and step by step installation procedure of SafeKit between two redundant Linux KVM servers

Installation of a SafeKit / KVM high availability cluster with real-time synchronous replication and failover between two redundant servers

Prerequisites

  • you need KVM installed on 2 Linux servers

Package installation on Linux

  • Install the free version of SafeKit on 2 Linux nodes with KVM services installed on both nodes
  • After the download of safekit_xx.bin package, execute it to extract the rpm and the safekitinstall script and then execute the safekitinstall script
  • Answer yes to firewall automatic configuration
  • Download the Linux module

    The module contains the files userconfig.xml, start_prim and stop_prim described in the internals tab
  • Put kvm.safe under /opt/safekit/Application_Modules/demo/ (create the demo directory if it does not exist)

Note    User's guide available here

Go to the Configuration tab

Configuration of a SafeKit / KVM high availability cluster with real-time synchronous replication and failover between two redundant servers

Prerequisites

The KVM configuration is presented with a virtual machine named vm1. You will have to repeat this configuration for all VMs that you want to replicate. SafeKit supports up to 25 virtual machines.

At this step, we suppose that a virtual machine named vm1 is existing and configured on node 1. The path of the vm1 image is /var/lib/libvirt/images. Before the SafeKit configuration, you have to make the following configuration

On node 1:

  • Stop vm1: virsh shutdown vm1
  • Create a vm1/ directory: mkdir -p /var/lib/libvirt/images/vm1/
  • Copy the vm1 image to the new location: cp -a /var/lib/libvirt/images/vm1.qcow2 /var/lib/libvirt/images/vm1/. The original VM image can be deleted as soon as tests with the new location are successfull.
  • Edit the vm1 configuration file: EDITOR=vi virsh edit vm1 and change the line:
    <source file='/var/lib/libvirt/images/vm1.qcow2'> by <source file='/var/lib/libvirt/images/vm1/vm1.qcow2'>
  • Set the cache option to 'none' in the same file, for data integraty in case of crash:
    <disk type='file' device='disk'> <driver name='qemu' type=’qcow2’ cache='none'/>
  • Close the vm1 configuration file
  • Disable vm1 automatic start: virsh autostart vm1 --disable
  • Create a configuration xml dump for vm1: virsh dumpxml vm1 > vm1.xml

On node 2:

  • Copy the xml configuration vm1.xml from node 1. Note: whenever vm1 configuration is changed on node 1, you must reapply the new configuration on node 2.
  • Create vm1 but do not start it: virsh define vm1.xml
  • Disable vm1 automatic start: virsh autostart vm1 --disable
  • Create the directory for the image location: mkdir -p /var/lib/libvirt/images/vm1/

Check cache='none' in virt-manager for vm1

KVM cache=none setting

Autostart must be disabled in virt-manager for vm1

KVM automatic start disabled

This operation must be repeated if you have another vm2 virtual machine. You will have also to repeat the SafeKit configuration below for vm2. At the end you will have two SafeKit KVM modules for vm1 and vm2. Each module are independant and thus the load can be shared between both KVM servers.

Snapshots

By default, snapshots of a virtual machine are not replicated. For replicating snapshots (after the configuration below):

  • Replicate the directory that contains the snapshot xml files: /var/lib/libvirt/qemu/snapshot/%VM_NAME% where VM_NAME is the name of the virtual machine (vm1)
    Edit userconfig.xml file in the "Advanced configuration" tab and insert the lines below into the <rfs> section:
    <replicated dir="/var/lib/libvirt/qemu/snapshot/%VM_NAME%" mode="read_only">
    </replicated>
    Save changes, then apply the new configuration on both nodes
  • Create snapshots only on the PRIM node either through virt-manager or a command line: virsh snapshot-create-as vm1 snapshot-name
    Note: when creating snapshot with a command line, you have to refresh the snapshot view into virt-manager.
  • Snapshots created on the PRIM node are operationnal on failover, but not listed on the other node.
    The command line for listing snapshot is: virsh snapshot-list vm1
    For importing a snapshot on the other node, you have to run the command: virsh snapshot-create --redefine vm1 /var/lib/libvirt/qemu/snapshot/vm1/snapshot-name

Configuration instructions

Warning  Important: all the SafeKit configuration is made from a single browser.

Launch the web console in a browser on one node by connecting to http://localhost:9010 (next image). You can also run the console in a browser on an external workstation by connecting to the physical IP address of one node.

Start the SafeKit web console for configuring the KVM module

Note   To secure the web console, see 11. Securing the SafeKit web console in the User's Guide.

Enter IP address of the first node and click on Confirm (next image)

SafeKit web console - first node in the KVM cluster

Click on New node and enter IP address of the second node (next image)
Then click on the red floppy disk to save the configuration (next image)

SafeKit web console - second node in the KVM cluster

Note   In the previous image, the save operation put the IP addresses in the file /var/safekit/cluster/cluster.xml and apply the distributed command /opt/safekit/safekit –H "*" -G which configures node 1 and node 2. So do not redo this operation on the other node. Check the connectivity and firewall between both nodes for troubleshooting.

In the Configuration tab, click on kvm.safe (xxx.safe in the next image) then enter vm1 as the module name and Confirm (the console finds kvm.safe in the demo/ directory that you previously filled)

SafeKit web console - start configuration of KVM module SafeKit web console - enter KVM module name

Click on Validate (next image)

SafeKit web console - enter KVM module nodes

Give the path of the images directory (/var/lib/libvirt/images in next image) where vm1/ has been created and the name of VM (vm1 in next image). /var/lib/libvirt/images/vm1/ will be replicated by SafeKit and the VM vm1 will be restarted in the SafeKit scripts.

SafeKit web console - enter KVM parameters

Click on Validate (previous image)

SafeKit web console - stop the KVM module before configuration the configuration

Click on Configure (previous image)

SafeKit web console - check the success green message of the KVM configuration

Check the success green message on both servers and click on Next (previous image). On Linux, you may have an error at this step if replicated directories are mount points. See this article to solve the problem.

We assume that node 1 is the referencial with the up-to-date data (otherwise do the following operation on node 2).
Select node 1 and click on start it (next image).
When you will start node 2, the first resynchronization will be made from node1 to node 2.
If in doubt, before this operation, we suggest you to make a copy of replicated directories before starting the cluster to avoid any errors.

SafeKit web console - select the KVM node with the up-to-date database

node 1 must reach the ALONE (green) state (next image) meaning that the start_prim script has been executed on node 1.
When node 1 reaches the ALONE (green) state, you can check that the KVM application is started on node 1.
If the state is ALONE (green) and if the application is not started, check the start_prim script: you can find output messages of the script in the Application Log available in the Control tab.
If node 1 does not reach the ALONE (green) state, analyze why with the Module Log available in the Control tab.
Note: in the next image, if the cluster is in the state [WAIT (red) not uptodate - STOP (red) not uptodate], stop the WAIT server and force its start as primary (click here to see the operation).

SafeKit web console - the first KVM node starts as primary and is alone

We assume that the services started automatically by SafeKit in the start_prim script are stopped on node 2.
Start node 2 (previous image) which becomes SECOND green (next image) after resynchronisation of all replicated directories (binary copy from node 1 to node 2).

SafeKit web console - the second KVM node starts as SECOND

The replication and failover is operational for vm1. vm1 is running on the PRIM node (previous image). Only modifications inside the KVM image defining vm1 are replicated in real-time in this state.

Test

Check with KVM virt-manager that vm1 is started on the primary server and stopped on the secondary server.

Stop the PRIM node by scrolling down the menu of the primary node and by clicking on Stop. Check that there is a failover on the SECOND node. And check the failover of vm1 with KVM virt-manager.

More information on tests in the User's Guide

Automatic start of the module at boot

Configure boot start (next image on the right side) configures the automatic boot of the module when the server boots. Do this configuration on node1 and node2 once the high availability solution is correctly running.

SafeKit web console - Automatic boot of KVM module

For reading the SafeKit logs, go to the Troubleshooting tab

For editing userconfig.xml, start_prim and stop_prim, go to the Advanced Configuration tab

Troubleshooting of a SafeKit / KVM high availability cluster with real-time synchronous replication and failover between two redundant servers

Module log

Read the module log to understand the reasons of a failover, of a waiting state on the availability of a resource etc...
To see the module log of the primary server (next image):

  • click on the Control tab
  • click on node 1/PRIM (it becomes blue) on the left side to select the server
  • click on Module Log
  • click on the Refresh icon (green arrows) to update the console
  • click on the floppy disk to save the module log in a .txt file and to analyze in a text editor

Repeat the same operation to see the module log of the secondary server.

SafeKit web console - Module Log of the PRIM KVM server

Application log

Read the application log to see the output messages of the stat_prim and stop_prim restart scripts.
To see the application log of the primary server (next image):

  • click on the Control tab
  • click on node 1/PRIM (it becomes blue) on the left side to select the server
  • click on Application Log to see messages when starting and stopping VM1
  • click on the Refresh icon (green arrows) to update the console
  • click on the floppy disk to save the application log in a .txt file and to analyze in a text editor

Repeat the same operation to see the application log of the secondary server.

SafeKit web console - Application Log of the PRIM KVM server

More information on troubleshooting in the User's Guide

For support, go to the Support tab

Advanced configuration of a SafeKit / KVM high availability cluster with real-time synchronous replication and failover between two redundant servers

In Advanced Configuration tab (next image), you can edit internal files of the module: bin/start_prim and bin/stop_prim and conf/userconfig.xml (next image on the left side). If you make change in the internal files here, you must apply the new configuration by a right click on the icon/xxx on the left side (next image): the interface will allow you to redeploy the modified files on both servers.

SafeKit web console - Advanced configuration of KVM module

More information on userconfig.xml in the User's Guide

Support of a SafeKit / KVM high availability cluster with real-time synchronous replication and failover between two redundant servers

For getting support on the call desk of https://support.evidian.com, get 2 Snaphots (2 .zip files), one for each server and upload them in the call desk tool (next image).

SafeKit web console - KVM snaphots for support

More information on support in the User's Guide

Internals of a SafeKit / KVM high availability cluster with synchronous replication and failover

Go to the Advanced Configuration tab, for editing these files

Internal files of the Linux kvm.safe module

userconfig.xml (description in the User's Guide)

<!-- Mirror Architecture with Real Time File Replication and Failover for KVM -->

<!DOCTYPE safe>
<safe>
  <!-- Set value to the path of the virtual machines repository -->
  <macro name="VM_PATH" value="/var/lib/libvirt/images" />
  <!-- Set value to the name of the virtual machine -->
  <macro name="VM_NAME" value="vm1" />

 <service mode="mirror" defaultprim="alone" maxloop="3" loop_interval="24" failover="on">
  <!-- Heartbeat Configuration --> 
  <heart>
    <heartbeat name="">
    </heartbeat>
  </heart>

  <!-- File Mirroring Configuration -->
  <rfs mountover="off" async="second" locktimeout="200" nbrei="3">
	<replicated dir="%VM_PATH%/%VM_NAME%" mode="read_only">
	</replicated>
	<!-- Uncomment for replicating the directory that contains snapshot xml files of the virtual machine
	<replicated dir="/var/lib/libvirt/qemu/snapshot/%VM_NAME%" mode="read_only">
	</replicated>
	-->	
  </rfs>

  <!-- User scripts Configuration -->
  <user>
    <var name="VM_PATH" value="%VM_PATH%/%VM_NAME%" />
    <var name="VM_NAME" value="%VM_NAME%" />
  </user>

 </service>
</safe>

start_prim

#!/bin/sh
# Script called on the primary server for starting application

# For logging into SafeKit log use:
# $SAFE/safekit printi | printe "message" 

# stdout goes into Application log
echo "Running start_prim $*" 

res=0

# Start VM_NAME
virsh start $VM_NAME
state=$(virsh list --all | grep " $VM_NAME " | awk '{ print $3}')
if ([ "x$state" == "x" ]) ; then
	res=1
	$SAFE/safekit printe "$VM_NAME not found"
else
	let i=1
	while ( [ $i -le 5 ] && [ "x$state" != "xrunning" ]); do
      sleep 5
      state=$(virsh list --all | grep " $VM_NAME " | awk '{ print $3}')
      let i=i+1
	done
	if ([ "x$state" != "xrunning" ]) ; then
		res=1
		$SAFE/safekit printe "$VM_NAME start failed"
	fi
fi

if [ $res -ne 0 ] ; then
  $SAFE/safekit printe "start_prim failed"
  
  # uncomment to stop SafeKit when critical
  $SAFE/safekit stop -i "start_prim"
fi

stop_prim

#!/bin/sh
# Script called on the primary server for stopping application

# For logging into SafeKit log use:
# $SAFE/safekit printi | printe "message" 

#----------------------------------------------------------
#
# 2 stop modes:
#
# - graceful stop
#   call standard application stop
#
# - force stop ($1=force)
#   kill application's processes
#
#----------------------------------------------------------

# stdout goes into Application log
echo "Running stop_prim $*" 

# Stop VM_NAME
virsh shutdown $VM_NAME
state=$(virsh list --all | grep " $VM_NAME " | awk '{ print $3}')
if ([ "x$state" == "x" ]) ; then
	res=1
	$SAFE/safekit printe "$VM_NAME not found"
else
	let i=1
	while ( [ $i -le 5 ] && [ "x$state" == "xrunning" ]); do
		# Stop VM_NAME
		virsh shutdown $VM_NAME
		sleep 5
      		state=$(virsh list --all | grep " $VM_NAME " | awk '{ print $3}')
      		let i=i+1
	done
	if ([ "x$state" == "xrunning" ]) ; then
		res=1
		$SAFE/safekit printe "$VM_NAME stop failed"
	fi
fi

res=0

# default: no action on forcestop
[ "$1" = "force" ] && exit 0

# Fill with your application stop call

[ $res -ne 0 ] && $SAFE/safekit printe "stop_prim failed"

Customers of SafeKit High Availability Software in all Business Activities

  • Best high availability use cases with SafeKit

    Best use cases [+]

    Like   OEM Software Like   Distributed Enterprise Like   Remote Sites
    Application Clustering Software for a Software Publisher High Availability Software in a Distributed Enterprise Business Continuity and Disaster Recovery without a replicated SAN
    A software publisher uses SafeKit as an OEM software for high availability of its application A distributed enterprise deploys SafeKit in many branches without specific IT skills SafeKit is deployed in two remote sites without the need for replicated bays of disks through a SAN

    Testimonials

    Like  The ideal product for a software publisher

    “SafeKit is the ideal application clustering solution for a software publisher. We currently have deployed more than 80 SafeKit clusters worldwide with our critical TV broadcasting application.

    Like  The product very easy to deploy for a reseller

    “WithNCompany has deployed in South Korea many SafeKit high availability solutions with the Hanwha Video Surveillance Platform. SafeKit is appreciated because the product is easy to install and very quickly deployed.”

    Like  The product to gain time for a system integrator

    “Thanks to a simple and powerful product, we gained time in the integration and validation of our critical projects like the supervision of Paris and Marseille metro lines (the control rooms).”


  • High availability of Video Surveillance Platforms with SafeKit

    Video surveillance and access control [+]

    In video surveillance systems and access control, Evidian SafeKit implements high availability with synchronous replication and failover of

    Sebastien Temoin, Technical and Innovation Director, NOEMIS, value added distributor of Milestone solutions:

    "SafeKit by Evidian is a professional solution making easy the redundancy of Milestone Management Server, Event Server, Log Server. The solution is easy to deploy, easy to maintain and can be added on existing installation. We have assisted integrators to deploy the solution on many projects such as city surveillance, datacenters, stadiums and other critical infrastructures. SafeKit is a great product, and Evidian provides great support. Happy to help if you have any questions."

    Use cases:


  • Harmonic has deployed more than 80 SafeKit clusters for high availability of its TV broadcasting application over satellites, terrestrials, cable, IPTV.

    TV broadcasting [+]

    Harmonic is using SafeKit as a software OEM high availability solution and deploys it with its TV broadcasting solutions over satellites, terrestrials, cable, IPTV.

    Over 80 SafeKit clusters are deployed on Windows for replication of Harmonic database and automatic failover of the critical application.

    Philippe Vidal, Product Manager, Harmonic says:

    “SafeKit is the ideal application clustering solution for a software publisher looking for a simple and economical high availability software. We are deploying SafeKit worldwide and we currently have more than 80 SafeKit clusters on Windows with our critical TV broadcasting application through terrestrial, satellite, cable and IP-TV. SafeKit implements the continuous and real-time replication of our database as well as the automatic failover of our application for software and hardware failures. Without modifying our application, it was possible for us to customize the installation of SafeKit. Since then, the time of preparation and implementation has been significantly reduced.”


  • The European Society of Warranties and Guarantees in Natixis uses SafeKit as a high availability solution for its applications.

    Finance [+]

    The European Society of Warranties and Guarantees in Natixis uses SafeKit as a high availability solution for its applications.

    Over 30 SafeKit clusters are deployed on Unix and Windows in Natixis.


  • Fives Syleps implements high availability of its ERP with SafeKit and deploys the solution in the food industry.

    Industry [+]

    Fives Syleps implements high availability of its ERP with SafeKit and deploys the solution in the food industry.

    Over 20 SafeKit clusters are deployed on Linux and Windows with Oracle.

    Testimonial of Fives Syleps:

    "The automated factories that we equip rely on our ERP. It is not possible that our ERP is out of service due to a computer failure. Otherwise, the whole activity of the factory stops.

    We chose the Evidian SafeKit high availability product because it is an easy to use solution. It is implemented on standard servers and does not require the use of shared disks on a SAN and load balancing network boxes.

    It allows servers to be put in remote computer rooms. In addition, the solution is homogeneous for Linux and Windows platforms. And it provides 3 functionalities: load balancing between servers, automatic failover and real-time data replication.”


  • Air traffic control systems supplier, Copperchase, deploys SafeKit high availability in airports.

    Air traffic control [+]

    Air traffic control systems supplier, Copperchase, deploys SafeKit high availability in airports.

    Over 20 SafeKit clusters are deployed on Windows.

    Tony Myers, Director of Business Development says:

    "By developing applications for air traffic control, Copperchase is in one of the most critical business activities. We absolutely need our applications to be available all the time. We have found with SafeKit a simple and complete clustering solution for our needs. This software combines in a single product load balancing, real time data replication with no data loss and automatic failover. This is why, Copperchase deploys SafeKit for air traffic control in airports in the UK and the 30 countries where we are present."


  • Software vendor Wellington IT deploys SafeKit high availability with its banking application for Credit Unions in Ireland and UK.

    Bank [+]

    Software vendor Wellington IT deploys SafeKit high availability with its banking application for Credit Unions in Ireland and UK.

    Over 25 SafeKit clusters are deployed on Linux with Oracle.

    Peter Knight, Sales Manager says:

    "Business continuity and disaster recovery are a major concern for our Locus banking application deployed in numerous Credit Unions around Ireland and the UK. We have found with SafeKit a simple and robust solution for high availability and synchronous replication between two servers with no data loss. With this software solution, we are not dependent on a specific and costly hardware clustering solution. It is a perfect tool to provide a software high availability option to an application of a software vendor."


  • Paris transport company (RATP) chose the SafeKit high availability and load balancing solution for the centralized control room of line 1 of the Paris subway.

    Transport [+]

    Paris transport company (RATP) chose the SafeKit high availability and load balancing solution for the centralized control room of line 1 of the Paris subway.

    20 SafeKit clusters are deployed on Windows and Linux.

    Stéphane Guilmin, RATP, Project manager says:

    "Automation of line 1 of the Paris subway is a major project for RATP, requiring a centralized command room (CCR) designed to resist IT failures. With SafeKit, we have three distinct advantages to meet this need. Firstly, SafeKit is a purely software solution that does not demand the use of shared disks on a SAN and network boxes for load balancing. It is very simple to separate our servers into separate machine rooms. Moreover, this clustering solution is homogeneous for our Windows and Linuxplatforms. SafeKit provides the three functions that we needed: load balancing between servers, automatic failover after an incident and real time data replication."

    And also, Philippe Marsol,  Atos BU Transport, Integration Manager says:

    “SafeKit is a simple and powerful product for application high availability. We have integrated SafeKit in our critical projects like the supervision of Paris metro Line 4 (the control room) or Marseille Line 1 and Line 2 (the operations center). Thanks to the simplicity of the product, we gained time for the integration and validation of the solution and we had also quick answers to our questions with a responsive Evidian team.”


  • The software integrator Systel deploys SafeKit high-availability solution in firefighter and emergency medical call centers.

    Healthcare [+]

    The software integrator Systel deploys SafeKit high-availability solution in firefighter and emergency medical call centers.

    Over 30 SafeKit clusters are deployed on Windows with SQL Server.

    Marc Pellas, CEO says:

    "SafeKit perfectly meets the needs of a software vendor. Its main advantage is that it brings in high availability through a software option that is added to our own multi-platform software suite. This way, we are not dependent on a specific and costly hardware clustering solution that is not only difficult to install and maintain, but also differs according to client environments. With SafeKit, our firefighter call centers are run with an integrated software clustering solution, which is the same for all our customers, is user friendly and for which we master the installation up to after-sales support."


  • ERP high availability and load balancing of the French army (DGA) are made with SafeKit.

    Government [+]

    ERP high availability and load balancing of the French army (DGA) are made with SafeKit.

    14 SafeKit clusters are deployed on Windows and Linux.

    Alexandre Barth, Systems administrator says:

    "Our production team implemented the SafeKit solution without any difficulty on 14 Windows and Linux clusters. Our critical activity is thus secure, with high-availability and load balancing functions. The advantages of this product are easy deployment and administration of clusters, on the one hand, and uniformity of the solution in the face of heterogeneous operating systems, on the other hand."

     


SafeKit High Availability Differentiators against Competition

SafeKit with the Hyper-V module or the KVM module Microsoft Hyper-V Cluster & VMware HA
SafeKit with Hyper-V VMware HA 1 Hyper-V cluster
Like  No shared disk - synchronous real-time replication instead with no data loss Dislike  Shared disk and specific extenal bay of disk
Like  Remote sites = no SAN for replication Dislike  Remote sites = replicated bays of disk across a SAN
Like  No specific IT skill to configure the system Dislike  Specific IT skills to configure the system

Note that the Hyper-V/SafeKit and KVM/SafeKit solutions are limited to replication and failover of 25 VMs.

VM HA with the SafeKit Hyper-V or KVM module Application HA with SafeKit application modules
SafeKit inside 2 hypervisors

VM HA

SafeKit replication and failover of full VM
SafeKit inside 2 virtual or physical machines

Application HA

SafeKit replication and failover at application level
Dislike  Replicates too much data (App+OS) Like  Replicates only application data
Dislike  Reboot of VM on hypervisor 2 if hypervisor 1 crashes: recovery time depending on the OS reboot Like  Quick recovery time with restart of App on OS2 if crash of VM1: around 1 mn or less (see RTO/RPO here)
Dislike  No application checker and software failover Like  Application checker and software failover
Dislike  Risk of downtime when fixing OS or App (single image) Like  Smooth update of OS1 or OS2 or App (two images)
Like  Generic solution for any application / OS Like  Simple integration with application modules

Software clustering vs hardware clustering >

A software cluster with SafeKit installed on two servers

Like  A simple software cluster with the SafeKit package just installed on two servers

Hardware clustering with external shared storage

Dislike  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

Like  SafeKit is a shared-nothing cluster: easy to deploy even in remote sites

Shared disk cluster: complex to deploy

Dislike  A shared disk cluster is complex to deploy

Application High Availability vs Full Virtual Machine High Availability >

SafeKit application high availability supports hardware failure, software failure, human errors

Like  Application HA supports hardware failure and software failure with a quick recovery time (RTO around 1 mn or less).
Smooth upgrade of application and OS possible server by server (version N and N+1 can coexist)

Virtual machines high availability supports only hardware failure with an recovery time depending on the OS reboot

Dislike  Full virtual machines HA supports only hardware failure with a VM reboot and a recovery time depending on the OS reboot.
Smooth upgrade not possible

High availability vs fault tolerance >

SafeKit high availability vs fault-tolerance

Like  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)

Fault tolerance system

Dislike  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 >

SafeKit synchronous replication with no data in case of failure

Like  SafeKit implements real-time synchronous replication with no data loss in case of failure

Asynchronous replication with data loss on failure

Dislike  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

Like  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

Dislike  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

Like  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

Dislike  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 >

No special network configuration in a SafeKit cluster

Like  No dedicated proxy servers and no special network configuration are required in a SafeKit cluster for virtual IP addresses

Special network configuration in other clusters

Dislike  Special network configuration is required in other clusters for virtual IP addresses. Note that SafeKit offers a health check adapted to load balancers

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

SafeKit Modules for Plug&Play High Availability Solutions