January 13th, 2026

Machine translation is used partially for this article. See the Japanese version for the original article.

Introduction

We tried building an HA cluster on Proxmox Virtual Environment (hereinafter called "Proxmox VE"). Proxmox VE is an open-source, free-to-use server virtualization platform that, like VMware ESXi and Hyper-V, allows you to easily create virtual machines, disks, and NICs via the GUI.

We created two virtual machines on Proxmox VE, installed EXPRESSCLUSTER X, and built a mirror disk type HA cluster. In this article, we introduce the procedure to build this HA cluster.

Contents

1. What is Proxmox Virtual Environment

Proxmox VE is an open-source server virtualization platform that supports KVM (full virtualization) and LXC (containers). It is basically free-to-use, and paid commercial support is available.

Like VMware ESXi and Hyper-V, you can create, run, and manage virtual machines (hereinafter called "VM") on physical servers. Operations are provided via the GUI accessible from a web browser, making VM creation and deletion easy. It supports various storage systems such as ZFS, Ceph, NFS, iSCSI, and LVM, and includes features such as VM backup/restore and snapshots. You can also operate Proxmox VE via the CLI and REST API to retrieve VM status and to stop VMs.

2. HA Cluster Configuration

We will build a mirror disk type HA cluster using a floating IP resource on Proxmox VE. The configuration diagram for the HA cluster to be built is as follows.

3. HA Cluster Building Procedure

3.1 Creating VMs

Create VMs for the client, server1, and server2 on Proxmox VE. The OS was installed using ISO images saved in Proxmox VE’s local storage. When actually setting up the HA cluster, please use an OS version supported by EXPRESSCLUSTER X. For the Linux version, system requirements also depend on the kernel module version, so please check not only the OS version but also the kernel module version.

In this article, as an example, we created VMs with the following settings. If you install Windows using VirtIO drivers, please also refer to the "Windows VirtIO Drivers" link below.

■OS

■Network and Hardware

To create VMs, access the Proxmox web interface via a web browser (https://<the IP address configured during Proxmox installation>:8006) and click [Create VM].

■General tab

VM IDs are assigned automatically. After entering the fields, click [Next].

■OS tab

After entering the fields, click [Next].

Windows

Linux

■System tab

After entering the fields, click [Next].

Windows

Linux

■Disks tab

Click [Add] to add a disk for the mirror disk. After entering the fields, click [Next].

Windows

Linux

■CPU tab

After entering the fields, click [Next].

■Memory tab

After entering the field, click [Next].

■Network tab

After entering the fields, click [Next].

Windows

Linux

Finally, click [Finish] to create the VM. After creation, start the VM and install the OS.

3.2 Creating a Mirror Disk Type HA Cluster

The HA cluster to be built is configured as follows. IIS (Windows) or Apache (Linux) is used for applications controlled by service resources or EXEC resources. Installation procedures and public directory configurations for IIS and Apache are omitted.

Windows version

■EXPRESSCLUSTER X version

■Failover group (failover)

■Monitor resources

Linux version

■EXPRESSCLUSTER X version

■Failover group (failover)

■Monitor resources

For details on installing EXPRESSCLUSTER X and building a mirror disk type HA cluster, please refer to the EXPRESSCLUSTER X Installation and Configuration Guide.

[Reference]
Documentation - Manuals

• EXPRESSCLUSTER X 5.3 > EXPRESSCLUSTER X 5.3 for Windows > Installation and Configuration Guide
• EXPRESSCLUSTER X 5.3 > EXPRESSCLUSTER X 5.3 for Linux > Installation and Configuration Guide

3.3 Configuring Forced Stop Resource

To prevent both-system activation, add a ping NP resolution resource and configure a forced stop resource. For details on both-system activation and forced stop resources, refer to the following:

For the target of the ping NP resolution resource, specify a device, other than the cluster servers, that can always respond to ping via the interconnect LAN registered in the configuration information. In this example, we specified the gateway of the Proxmox host as the ping responder. When setting up an NP resolution resource in practice, choose the appropriate NP resolution method and target that fit your HA cluster environment.

On Proxmox environment, there is no corresponding forced stop resource, so use a custom forced stop resource. Proxmox provides a REST API for operations such as controlling VMs. By calling this API to stop or reboot VMs, you can implement a forced stop. Sample scripts can be downloaded from the links below. If you use the samples, change “_” in the file name to “.”.

Forced stop script sample (Windows)
Forced stop script sample (Linux)

For details on how to configure a custom forced stop resource, please refer to the following.

4. Checking the Operation

We will check whether the HA cluster is properly built by following these steps:

Windows version

Linux version

These steps check that it can be checked that it is possible to connect to the HA cluster via the floating IP address before and after failover, and that the disk is mirrored.

Also, we will cause a network partition and check the behavior of the forced stop resource. In order to cause a network partition, we configure a firewall to block all communication between the servers in the HA cluster. This causes the heartbeats between the servers to disconnect, but ping communication to the gateway of the Proxmox host from the servers is still possible, so each server decides that there is a problem on the other server and tries to start the failover group. However, on the standby server, it will perform the forced stop before trying to start the failover group, check that the active server has stopped, and then start the failover group. This prevents both-system activation.

Below is an example from the Linux version. After the standby server detects the active server’s down state, the syslog output is as follows. You can see that the forced stop script executed before the failover group started.

Conclusion

In this article, we installed EXPRESSCLUSTER X on VMs created on Proxmox VE and tried to build a mirror disk type HA cluster. EXPRESSCLUSTER X is designed to be independent of any virtualization platform, so it can be used as long as the guest OS is included in the EXPRESSCLUSTER X system requirements for the OS. Only the forced stop resource needs to leverage the virtualization platform’s functions, and we implemented it using a custom forced stop script.

If you consider introducing the configuration described in this article, you can perform a validation with the trial module of EXPRESSCLUSTER X. Please do not hesitate to contact us if you have any questions.