eviden-logo

Evidian > Products > SafeKit: Simple, Cost-Effective High Availability Software > Cloud: The Simplest High Availability Cluster with Synchronous Real-Time Replication and Failover

Cloud: The Simplest High Availability Cluster with Synchronous Real-Time Replication and Failover

Evidian SafeKit

How the Evidian SafeKit software simply implements a high availability cluster in Cloud?

The solution in Cloud

Evidian SafeKit brings high availability in Cloud between two Windows or Linux redundant servers.

This article explains how to implement quickly a Cloud cluster without shared disk and without specific skills.

A generic product

Note that SafeKit is a generic product on Windows and Linux.

You can implement with the same product real-time replication and failover of any file directory and service, database, complete Hyper-V or KVM virtual machines, Docker, Kubernetes, Cloud applications (see all solutions).

Architecture

SafeKit mirror cluster with real-time replication and failover in Cloud?

How it works in Cloud?

  • The servers are running in different availability zones.
  • The critical application is running on the PRIM server.
  • Users are connected to a primary/secondary virtual IP address which is configured in the Cloud load balancer.
  • SafeKit provides a generic health check for the load balancer.
    On the PRIM server, the health check returns OK to the load balancer and NOK on the SECOND server.
  • In each server, SafeKit monitors the critical application with process checkers and custom checkers.
  • SafeKit restarts automatically the critical application when there is a software failure or a hardware failure thanks to restart scripts.
  • SafeKit makes synchronous real-time replication of files containing critical data.
  • A connector for the SafeKit web console is installed in each server.
    Thus, the high availability cluster can be managed in a very simple way to avoid human errors.

How the SafeKit mirror cluster works?

Step 1. Real-time replication

Server 1 (PRIM) runs the application. Clients are connected to a virtual IP address. SafeKit replicates in real time modifications made inside files through the network.

File replication at byte level in a mirror cluster

The replication is synchronous with no data loss on failure contrary to asynchronous replication.
You just have to configure the names of directories to replicate in SafeKit. There are no pre-requisites on disk organization. Directories may be located in the system disk.

Step 2. Automatic failover

When Server 1 fails, Server 2 takes over. SafeKit switches the virtual IP address and restarts the application automatically on Server 2.
The application finds the files replicated by SafeKit uptodate on Server 2. The application continues to run on Server 2 by locally modifying its files that are no longer replicated to Server 1.

Failover in a mirror cluster

The failover time is equal to the fault-detection time (30 seconds by default) plus the application start-up time.

Step 3. Automatic failback

Failback involves restarting Server 1 after fixing the problem that caused it to fail.
SafeKit automatically resynchronizes the files, updating only the files modified on Server 2 while Server 1 was halted.

Failback in a mirror cluster

Failback takes place without disturbing the application, which can continue running on Server 2.

Step 4. Back to normal

After reintegration, the files are once again in mirror mode, as in step 1. The system is back in high-availability mode, with the application running on Server 2 and SafeKit replicating file updates to Server 1.

Return to normal operation in a mirror cluster

If the administrator wishes the application to run on Server 1, he/she can execute a "swap" command either manually at an appropriate time, or automatically through configuration.

๐Ÿ” SafeKit High Availability Navigation Hub

Explore SafeKit: Features, technical videos, documentation, and free trial
Resource Type Description Direct Link
Features Why Choose SafeKit for Simple and Cost-Effective High Availability? View Features
Partners SafeKit: The Benchmark in High Availability for Partners SafeKit for Partners
VM vs App HA SafeKit: High Availability (HA) and Redundancy Choices VM/App Choice
Typical Usage Typical usage with SafeKit and Limitations Usage and Limitations
Videos SafeKit: Technical Demonstrations and Tutorials Watch Videos
Mirror Cluster How the SafeKit mirror cluster works (real-time file replication and failover)? Mirror Cluster
Farm Cluster How the SafeKit farm cluster works (network load balancing and failover)? Farm Cluster
Differentiators Comparison of SafeKit with Traditional High Availability (HA) Clusters View Benefits
Resources SafeKit High Availability Resources, Downloads, and Documentation Access Resources
Application Modules SafeKit Application Module Library: Ready-to-Use Solutions Browse Modules