Evidian > Products > High Availability Software - Zero Extra Hardware > 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 > Products > High Availability Software - Zero Extra Hardware > 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 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
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).
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:
On node 2:
Check cache='none' in virt-manager for vm1
Autostart must be disabled in virt-manager for vm1
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.
By default, snapshots of a virtual machine are not replicated. For replicating snapshots (after the configuration below):
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.
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)
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)
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)
Click on Validate (next image)
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.
Click on Validate (previous image)
Click on Configure (previous image)
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.
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).
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).
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.
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
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.
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):
Repeat the same operation to see the module log of the secondary server.
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):
Repeat the same operation to see the application log of the secondary server.
More information on troubleshooting in the User's Guide
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.
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).
Go to the Advanced Configuration tab, for editing these files
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"
 OEM Software |
Distributed Enterprise |
Remote Sites |
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| 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 |
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“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.” |
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“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.” |
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“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).” |
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 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.
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.
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.
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.
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.
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.
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.
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 with the Hyper-V module or the KVM module | Microsoft Hyper-V Cluster & VMware HA |
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 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 |
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 |
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SafeKit inside 2 hypervisors
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SafeKit inside 2 virtual or physical machines
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| Replicates too much 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 VM1: around 1 mn or less (see RTO/RPO here) |
| No application checker and software failover |
Application checker and software failover |
| Risk of downtime when fixing OS or App (single image) |
Smooth update of OS1 or OS2 or App (two images) |
| Generic solution for any application / OS |
Simple integration with application modules |
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Application High Availability vs Full Virtual Machine High Availability > |
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Byte-level file replication vs block-level disk replication > |
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Virtual IP address |
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Network load balancing and failover |
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Windows farm |
Linux farm |
| Generic farm > | Generic farm > |
| Microsoft IIS > | - |
| Apache > | Apache > |
| Amazon AWS farm > | Amazon AWS farm > |
| Microsoft Azure farm > | Microsoft Azure farm > |
| Google GCP farm > | Google GCP farm > |
| Other cloud > | Other cloud > |
