Read carefully these items before starting: This guide explains how to set up a hyperv cluster for Hyper-V using SafeKit, ensuring automatic failover and synchronous replication without the need for shared storage.
For help, you can use SafeKit AI ๐ค.
hyperv.safe application module.Resynchronization time after a failure (step 3)
The solution is described here: Simple Hyper-V High Availability Without Shared Storage (SAN)
โฌ๏ธ Download hyperv.safe (Windows) >
Read carefully these items before starting: VM1. Read carefully “1. Prerequisites” for the organization of VM1 files , otherwise recovery on the secondary node may fail with inconsistent data.For SafeKit replication, all VM1 virtual machine files (configuration file, virtual hard disk, etc.) must be stored in the same folder, even though this is not the default behavior of HyperโV (e.g., D:/Repli-Hyper-V/VM1, where VM1 is the name of the virtual machine).
If all the files of VM1 are not in the same folder, use Hyper-V manager:
Take a snapshot or your VM before starting the procedure.VM1 must only be created on a single node. The only thing to create on the other node is the VM1 directory (D:/Repli-Hyper-V/VM1).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.HyperโV module (hyperv.safe) failover may fail if VM migration prerequisites are not met. To detect compatibility issues between HyperโV nodes (hardware, network, configuration), see KB SK-0088 in this document.http://localhost:9010.admin as user name and the password defined during installation.You can also run the console in a browser on a workstation external to the cluster.
The configuration of SafeKit is done on both nodes from a single browser.
To secure the web console, see 11. Securing the SafeKit web service in the User's Guide.
Tab key to check connectivity and fill node names. If either node1 or node2 has a red color, check connectivity of the browser to both nodes and check firewall on both nodes for troubleshooting.Save and apply to save the configuration.Success โ
message on both nodes.Failure โ occurs on one node, open the โผ accordion for that node and review the messages. Note that you can use the SafeKit AI ๐ค for assistance.If you want, you can add a new `LAN and nodes` ( first โ) to create a second heartbeat and a dedicated replication network.If you click on `Advanced configuration`, the `cluster.xml` file is displayed. This file is automatically populated by the console and deployed on the nodes.
New module, click on the hyperv.safe module.In the blue banner at the top, ๐ `node1` represents the console connection node. This node relays requests to `node2` when required.The console looks for `xxx.safe` in the `Application_Modules/generic/` directory on the connection node (`node1`) if you placed a module there during installation.
Automatic start of the module at boot without delay.Heartbeat network on which the replication is made. But, you can define a private network if necessary (by adding a LAN at step 3).VM_PATH, the root path of the replicated directory (D:/Repli-Hyper-V).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. Do not perform partial replication, as failover will not work.
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, if the application inside the VM fails, it is restarted.
This will be the case, for example, when switching between primary and secondary roles.
You do not need to configure a virtual IP address. VM1 will be rebooted on the secondary Hyper-V with its physical IP address, and this IP address will be rerouted.When you apply the SafeKit configuration, the `Automatic Start Action` of the virtual machine is set to `Nothing` in Hyper-V. This ensures that the VM does not start automatically when the HyperโV host starts, but is instead started only when the module itself is started.
The custom checker sends heartbeat messages from the host to the VM at regular intervals. It is then the job of the Hyper-V Heartbeat Service installed in the VM to send a response to each of these heartbeat messages.
If the Hyper-V Heartbeat Service does not respond to the message (VM locked up, crashed or ceased to function), then the custom checker executes an action to restart the VM on the same Hyper-V node or on the other.
Checkers / Custom (see image).Resource name (example VM1). Resource name identifies the virtual machine with a resource name in SafeKit: custom.VM1.restart in Action, the VM is restarted on the same Hyper-V node. After 3 unsuccessful restarts in 24 hours, the SafeKit hyperv module stops on the primary node and there is a failover of the VM on the secondary node.stopstart in Action, there is a direct failover on the other Hyper-V node as soon as the VM does not respond to heartbeats.For maintenance, if you want to stop the virtual machine, the custom checker will restart it automatically. To avoid that, you can temporarly suspend the checker ๐ผ๏ธ. Or you can remove it by deleting the configuration line in the console.Itโs the same when you want to restore a checkpoint. Hyper-V will stop the VM to perform the operation, and the VM checker may react negatively by automatically restarting the VM. To avoid this, suspend the checker ๐ผ๏ธ before proceeding with the operation.
Save and apply the configuration and scripts on both nodes.
Success โ
message on both nodes and click on Monitor modules.Failure โ occurs on one node, open the โผ accordion for that node and review the messages. Note that you can use the SafeKit AI ๐ค for assistance.
VM1/, select it and โฏ Force start โถ As primary.When node 2 will be started, all data will be copied from node 1 to node 2.
If you make the wrong choice, you run the risk of synchronizing outdated data on both nodes.It is also assumed that `VM1` is stopped on node 1 so that SafeKit installs the replication mechanisms and then starts `VM1` in the `start_prim` script.Use `Start` for subsequent starts: SafeKit retains the most up-to-date server. Starting `As primary` is a special start-up the first time or during exceptional operations.
start_prim script has been executed on node 1.If ALONE (green) is not reached or if VM1 is not started, analyze why with the module log ๐ผ๏ธ of node 1.
node1 to open the module log and look for error messages such as a checker detecting an error and stopping the module.start_prim in the log: output messages of the script are displayed on the right and errors can be detected such as VM1 incorrectly started.If the cluster is in `WAIT (red) not uptodate, STOP (red) not uptodate` state, stop the WAIT node and force its start as primary ๐ผ๏ธ.
Start node 2 with its contextual menu.Node 2 stays in the SECOND (orange) state while resynchronizing the replicated directories (copy from node 1 to node 2).This may take a while depending on the size of files to resynchronize in replicated directories and the network bandwidth.
To see the progress of the copy, see the module log ๐ผ๏ธ and the replication resources ๐ผ๏ธ of node 2. Use the SafeKit AI ๐ค for assistance with log messages.
When using Hyper-V differencing disks, only the differencing disk needs resynchronization after the initial sync, saving time for large virtual hard disks.
VM1 running on the PRIM node and not running on the SECOND node.Only changes inside files are replicated in real time in this state.
Stop.VM1 is running on node 2.If ALONE (green) is not reached on node2 or if VM1 is not started, analyze why with the module log ๐ผ๏ธ of node 2.
node2 to open the module log and look for error messages such as a checker detecting an error and stopping the module.start_prim in the log: output messages of the script are displayed on the right and errors can be detected such as VM1 incorrectly started.As the `start_prim` script imports the virtual machine on node 2, the failover can fail because of Hyper-V settings (see KB SK-0088 in this document).If everything is okay, initiate a start on node1, which will resynchronize the replicated directories from node2.If things go wrong, stop node2 and force the start as primary ๐ผ๏ธ of node1, which will restart with its locally healthy data at the time of the stop.
Note that you have a ๐ **timeline ๐ผ๏ธ** that can be helpful to understand what happens in the cluster.
Checkers / Splitbrain (see image) to edit the splitbrain parameters.Save and apply the new configuration to redeploy it on both nodes (module must be stopped on both nodes to save and apply).Parameters :
Resource name identifies the witness with a resource name: splitbrain.witness. You can change this value to identify the witness.Witness address is the argument for a ping when a node goes from PRIM to ALONE or from SECOND to ALONE. Change this value with the IP of the witness (a robust element, typically a router).
If you want an automatic restart or failover when a critical service inside the VM fails, you can configure the Recovery properties of the service (see image).
First you must configure the VM custom checker previously described.
And then in Microsoft Service Manager inside the VM, select your critical service and in the recovery property of the service, you just have to configure shutdown of the VM when the critical service fails.
For that, in the Recovery options of your critical service, choose “Run a Program " on failures and in Run program options, set”C:/Windows/System32/shutdown.exe " and in “Command line parameters”, set /s /c “service fails”.
Of course, you can implement more subtle recovery with your own scripts. But just be aware that shutting down the VM will enable the custom checker in the host. The custom checker will detect that the Hyper-V heartbeat is no more responding and will restart the VM on the same Hyper-V server or will make a failover on the other Hyper-V server (depending on its configuration).
To test the feature, use Task Manager and kill the process (End task) associated to the critical service. A clean stop of the service through Service Manager or the “net stop” command does not trigger the recovery action inside Windows Service Manager.
Snapshots (2 .zip files), one for each node.
In this video, discover how SafeKit implements high availability for Hyper-V without the complexity of a SAN. Learn to configure virtual machine replication across two nodes to ensure seamless failover for your critical virtualized workloads. Although this demonstration uses Hyper-V on Windows, the solution works identically with KVM on Linux.
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Explore SafeKit: Features, technical videos, documentation, and free trial
| Resource Type | Description | Direct Link |
|---|---|---|
| Key Features | Why Choose SafeKit for Simple and Cost-Effective High Availability? | See Why Choose SafeKit for High Availability |
| Use Cases | Explore How SafeKit Ensures the High Availability of Critical Infrastructure | See All Use Cases (OEM Software, Edge Servers, SCADA, and more) |
| Deployment Model | All-in-One SANless HA: Shared-Nothing Software Clustering | See SafeKit All-in-One SANless HA |
| HA Strategies | SafeKit: Infrastructure (VM) vs. Application-Level High Availability | See SafeKit HA & Redundancy: VM vs. Application Level |
| Technical Specifications | Technical Limitations for SafeKit Clustering | See SafeKit High Availability Limitations |
| Proof of Concept | SafeKit: High Availability Configuration & Failover Demos | See SafeKit Failover Tutorials |
| Architecture | How the SafeKit Mirror Cluster works (Real-Time Replication & Failover) | See SafeKit Mirror Cluster: Real-Time Replication & Failover |
| Architecture | How the SafeKit Farm Cluster works (Network Load Balancing & Failover) | See SafeKit Farm Cluster: Network Load Balancing & Failover |
| Competitive Advantages | Comparison: SafeKit vs. Traditional High Availability (HA) Clusters | See SafeKit vs. Traditional HA Cluster Comparison |
| Technical Resources | SafeKit High Availability: Documentation, Downloads & Trial | See SafeKit HA Free Trial & Technical Documentation |
| Pre-configured Solutions | SafeKit Application Module Library: Ready-to-Use HA Solutions | See SafeKit High Availability Application Modules |