Microsoft Azure High Availability: SafeKit Synchronous Replication & Failover

Evidian SafeKit brings high availability to Azure between two virtual machines in two Availability Zones (AZ).

This article explains how to implement quickly a Azure cluster without cloud shared disks and without specific skills.

The principle of the solution is to define the folders where the Azure application 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 Synchronous Real-time File Replication into a single engine.

This eliminates the "house of cards" risk where 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 Azure application HA.

How does SafeKit handle Uniform Deployment and the Cloud Virtual IP?

SafeKit is a cloud-agnostic solution, meaning the deployment process and architecture stay the same across on-premises servers and all major cloud providers. The only architectural difference lies in how the Virtual IP is presented to the network:

• On-Premises: SafeKit manages the VIP directly by sending GARP (Gratuitous ARP) packets to local switches, moving the IP between nodes instantly.
• In the Cloud: Since Cloud networks do not support GARP, the Virtual IP is hosted by a Cloud Load Balancer.

  SafeKit provides the health probe to determine which node is the primary one. This allows the Load Balancer to detect the active node in real-time and route traffic to it automatically, ensuring seamless failover across Availability Zones.

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

SafeKit differentiates itself from traditional Azure clusters through its shared-nothing architecture and simplified deployment. While most enterprise solutions require complex management of cloud shared disks, 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 Azure application 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 Azure application 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 Azure application 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 Azure 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 Cloud Shared Disk Costs: SafeKit uses a shared-nothing architecture that works with local disks.
• No Enterprise Edition Required: While native database 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 your Azure application against failures.