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 hyperv.safe and a free trial are offered in the installation instructions section.
Note that you can implement with the same product real-time replication and failover of other applications (database or other): see 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.
How to implement Hyper-V replication automatic failover and load balancing of VMs with the SafeKit software (no shared disk)?
Principle
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 the VM on the other Hyper-V server. And when the failed server is restarted, there is an automatic reintegration of VM files without stopping the VM 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.
Features
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.
Video demonstrating Hyper-V replication automatic failover and load balancing of VMs
In 10 minutes, the video shows all the steps to implement replication automatic failover and load balancing of VMs with SafeKit:
export virtual machines (VMs) in a special directory that will be replicated by SafeKit
configure a SafeKit mirror module for each VM
see how to migrate a VM from one Hyper-V server to the other one with a simple click on "Swap"
understand what happens for a user when a VM is migrated, when a Hyper-V server is rebooted, when a Hyper-V server crashes
Supports multiple heartbeats and vitual IP addresses
Offers configurable software, hardware and network checkers
For the quorum, does not require a special disk or a third machine or a dedicated link between both servers
Automatic failover of Hyper-V services with a recovery time in the order of one minute
Automatic failback when a server comes back after a failure (no manual operation)
A very simple console to deploy the solution and to maintain it afterwards for end-customer
Supports human errors (40% of causes of unavailability) thanks to its simplicity
Supports software failures (40% of causes of unavailability): regression on software update (version N and N+1 can coexist), Operating System frozen, software bug
Supports hardware and environment failures (20% of causes of unavailability), including the complete failure of a computer room with 2 nodes in two remote sites
What is the recovery time (RTO) [+]
RTO is the time during which the application is unavailable in case of failure. RTO of the SafeKit mirror solution is in the order of 1 mn.
For a hardware failure, RTO = heartbeat timeout (default 30 s, can be changed in userconfig.xml) + time to restart Hyper-V services.
For a software failure or an administrator restart, RTO = time to (cleanly) stop Hyper-V services + time to restart them.
Be careful, with solutions that reboot a full virtual machine in case of failure, the RTO is unpredictable as manual operations may be required after a hardware crash to reboot the virtual machine.
What is the data loss (RPO) [+]
RPO reflects the data loss in case of failure. RPO of the SafeKit mirror solution is 0 as the replication is synchronous and real-time.
Be careful, with asynchronous replication, RPO is not 0 and there is data loss in case of failure when the application restarts on the secondary server.
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.”
Finance [+]
The European Society of Warranties and Guarantees in Natixis uses SafeKit as a high availability solution for its applications.
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.”
“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 Unix platforms. 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.”
“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.”
“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.”
Installation of SafeKit for Hyper-V high availability with synchronous replication and failover
Put hyperv.safe under C:\safekit\Application_Modules\demo\ (create the demo directory if it does not exist)
To open firewall, start a command line as administrator, goto C:\safekit\private\bin and type .\firewallcfg.cmd add on both nodes
Configuration instructions
The Hyper-V 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.
Important: all the configuration is made from a single browser.
Launch the web console in a browser by connecting to http://localhost:9010 (next image)
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)
Click on the red floppy disk to save the configuration (previous image)
In the Configuration tab, click on hyperv.safe (xxx.safe in the next image) then enter VM1 as the module name and Confirm
Click on Validate (next image)
Before the SafeKit configuration, you have to make a configuration in Hyper-V manager (see demonstration):
Export with the name VM1 the target VM in a directory that will be replicated, for example: D:\Repli-Hyper-V
Remove the target VM from the inventory of Hyper-V manager
Import the VM1 virtual machine into Hyper-V manager
Then in SafeKit configuration (next image), give the path of the replicated directory (D:\Repli-Hyper-V in next image) where the VM has been exported and enter the exported VM name (VM1 in next image).
Click on Validate (previous image)
Click on Configure (previous image)
Check the success green message on both servers and click on Next (previous image).
Select the node with the most up-to-date replicated directories and click on start it to make the first resynchronization in the right direction (previous image). Before this operation, we suggest you to make a copy of replicated directories before starting the cluster to avoid any errors.
Start the second node (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 Hyper-V files defining VM1 are replicated in real-time in this state.
Tests
Check with Hyper-V 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 Hyper-V manager.
To understand what happens in the cluster, check the SafeKit logs of the primary server and the secondary server.
To see the module log of the primary server (next image):
click on the Control tab
click on W12R2server74/PRIM (it becomes blue) on the left side
click on Module Log
click on the Refresh icon (green arrows) to update the console
check Verbose log to see all messages
click on the floppy disk to save the module log in a .txt file and to analyze in a text editor
To see the application log of the primary server (next image):
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
To see the logs of the secondary server (previous image), click on W12R2server75/SECOND (it will become blue) on the left side and repeat the same operations.
In the secondary module log, you will find the volume and the reintegration time of replicated data.
Advanced configuration
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 blue icon/xxx on the left side (next image): the interface will allow you to redeploy the modified files on both servers.
Configure boot start (next image on the right side) configures the automatic boot of the module when the server boots. Do this configuration on both servers once the high availability solution is correctly running.
Support
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).
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