The Simplest Linux High Availability: 2-Node Synchronous Replication & Failover

SafeKit brings high availability to Linux between two servers of any brand.

This article explains how to implement quickly a Linux cluster without shared storage on a SAN and without specific skills.

The principle of the solution is to define the folders where the Linux data resides, its services, a virtual IP, and checkers.

SafeKit then implements real-time replication and automatic failover to ensure continuous service availability.

Why choose a unified All-in-One HA solution over fragmented tools?

Unlike "bolt-on" solutions that combine separate products for replication and clustering, SafeKit integrates Virtual IP, Automatic Failover, Automatic Failback and Real-time File Replication into a single engine.

This eliminates the "house of cards" risk where OS updates break fragile links between disparate tools, provides a single point of accountability for the entire HA stack, and reduces human error by providing a single interface for Linux HA.

Should I choose high availability at the application level or the virtual machine (VM) level?

With SafeKit, you have the flexibility to choose the redundancy model that fits your needs.

VM-level redundancy (for Hyper-V or KVM) is the simplest to implement as it replicates the entire virtual machine, requiring no knowledge of the internal application.

Alternatively, application-level redundancy is more granular; it only replicates specific data folders and restarts the application services rather than the entire OS.

While VM-level HA is easier to set up, application-level HA is hypervisor-agnostic and can run across physical, virtual, or cloud environments.

What are the distinctive advantages of SafeKit for Linux high availability compared to competitors?

SafeKit differentiates itself from traditional Linux clusters through its shared-nothing architecture and simplified deployment. While most enterprise solutions require complex replication deployment or expensive SAN storage, SafeKit provides:

• Synchronous Replication with Zero Data Loss: SafeKit implements 100% synchronous replication, ensuring total data integrity for transactional applications. In the event of a failure, there is zero data loss (RPO=0). Furthermore, SafeKit is capable of replicating not only the Linux databases but any other data folders (logs, configuration files, etc.), ensuring the entire environment is mirrored.
• Simplified 2-Node Clustering: Unlike standard clusters that often require a "witness" (a 3rd node, disk, file share) to maintain a quorum, SafeKit delivers full high availability with just two redundant servers, reducing infrastructure costs and complexity.
  Learn more about our heartbeat and quorum mechanism.
• Unified Management: Administrators can manage Linux failover, data replication, and monitoring through a single SafeKit console. This makes high availability accessible to teams without specialized "cluster admin" expertise.
• Custom Checkers: SafeKit goes beyond basic service monitoring; it offers checkers to monitor the health of the Linux process. The system is highly extensible, allowing for the addition of custom checkers tailored to your environment.

How does SafeKit reduce the TCO (Total Cost of Ownership) for Linux compared to standard clustering?

Unlike traditional high-availability solutions, SafeKit is designed to operate with the absolute minimum infrastructure overhead, without compromising reliability. Key savings compared to traditional failover cluster include:

• Zero Storage Costs: SafeKit uses a shared-nothing architecture that works with local disks. This removes the need for expensive SAN hardware, iSCSI networks, or complex vSAN configurations.
• No Enterprise Edition Required: While native replication mechanim may require expensive Enterprise licensing, SafeKit does not need the Enterprise edition. It works seamlessly with standard edition and even the free edition, providing high-end availability at a fraction of the cost.
• True 2-Node Efficiency: Unlike standard clusters that often require a "witness" (a 3rd node, disk, or file share) to maintain a quorum, SafeKit delivers full high availability with just two redundant servers.
• No Forced Subscriptions: SafeKit offers a perpetual license. You own your software, avoiding the "subscription trap" and unpredictable annual price hikes common with modern cloud-only or subscription-based models.
• Low Operational Expense (OPEX): As a plug-and-play solution, it requires no specialized training or expensive external consultancy for maintenance, unlike complex open-source clustering tools.
• CPU-Independent Pricing: Licensing is independent of the number of CPUs or cores. With just two licenses for two nodes, you can protect Linux against failures.