Managing High Availability and Failover in FreeBSD

Jul 19, 2023 • FreeBSDSoftware

FreeBSD has been known for its robustness and performance since its inception. It comes loaded with a multitude of features that ensure the availability of your services and maintain redundancy. This article will guide you through the key processes and underlying structures that allow successful management of high availability and failover in FreeBSD. We advise potential users to look into FreeBSD system administration before diving into these more complex topics.

Deciphering High Availability and Failover

In the realm of modern computing, service continuity is paramount. High Availability (HA) and Failover are mechanisms aimed at ensuring this continuity. Both work together to minimize service downtime.

High Availability points to the system’s capability to function continuously without significant downtime despite one or more failures within the system. Failover is the process through which a system automatically hands off its processes to a standby system in the event of a failure.

Using CARP for High Availability

The Common Address Redundancy Protocol (CARP) plays a pivotal role in ensuring high availability in FreeBSD. By using CARP, you can have multiple hosts on the same network segment that use the same IP address. When the master host (primary device holding the CARP IP) goes down, one of the backups will take up the role, thereby maintaining the service’s availability.

To configure CARP in FreeBSD, navigate to /etc/rc.conf and add the following:

ifconfig_em0="inet netmask"
ifconfig_em0_alias0="inet vhid 1 pass mypassword alias"

This configuration creates a CARP virtual interface on em0, with a defined virtual host ID (vhid) and password for synchronization.

The configuration of the backup host would be similar, substituting vhid 1 with vhid 2. The rest remains the same.

For more information on IP configurations, check out our guide on FreeBSD Network Configuration and Troubleshooting.

Implementing HAST for Failover

Highly Available Storage (HAST) allows for transparent storage of the same data across multiple servers for immediate failover. It utilizes the geostat framework to provide data consistency and avoid conflicts between nodes.

To create a new HAST resource, run the hastctl create <resource> command, where <resource> is the name of the resource. Following creation, synchronize the resources using hastd, and include this resource in your hast.conf.

resource data {
        on carp1 {
                local /dev/ad4s1

You can find more information on disk management in our Disk Management and File Systems guide.

Monitoring Your System

High availability and failover management rely heavily on consistent monitoring of your system. FreeBSD provides robust tools for System Monitoring for real-time analysis and debugging.

Bottom Line

By optimally utilizing the high availability and failover features of FreeBSD, you can manage a robust, efficient, and resilient infrastructure. These mechanisms, complemented by timely updates, proper user and group management, system optimization, and effective troubleshooting, carve a path towards the full realization of FreeBSD’s robust capabilities. Dive deeper into these other aspects at our FreeBSD Blog.

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