--- canonical: https://safekit.evidian.com/products/high-availability-software-for-application-clustering/docker-container-high-availability-cluster-synchronous-replication-failover/ --- SafeKit: Docker High Availability & Real-Time Data Replication Software - SafeKit HA [![Evidian Logo](/wp-content/uploads/2026/01/eviden-logo-black-265-54.png)](https://eviden.com) * [SafeKit](/products/high-availability-software-for-application-clustering/) + - * SafeKit --- * [Home SafeKit](https://safekit.evidian.com/) * [Elevator pitch](https://safekit.evidian.com/products/high-availability-software-for-application-clustering/high-availability-software-ha-cluster-windows-linux/) * [Customer use cases](https://safekit.evidian.com/products/high-availability-software-for-application-clustering/#safekit-use-cases) - * Use cases --- * [Best/Worst Use Cases](https://safekit.evidian.com/products/high-availability-software-for-application-clustering/best-worst-use-cases-high-availability/) * [OEM use case for a software publisher](https://safekit.evidian.com/products/high-availability-software-for-application-clustering/application-clustering-software/) * [Distributed Enterprise use case](https://safekit.evidian.com/products/high-availability-software-for-application-clustering/business-continuity-software/) * [Remote sites and disaster recovery use case](https://safekit.evidian.com/products/high-availability-software-for-application-clustering/business-continuity-and-disaster-recovery-software/) - * High Availability in Physical Security Market --- * [Physical Security Software](https://safekit.evidian.com/products/high-availability-software-for-application-clustering/physical-security-software-redundancy/) * [Video Management Software (VMS)](https://safekit.evidian.com/products/high-availability-software-for-application-clustering/video-management-software-vms-redundancy/) * [Electronic Access Control Software (EACS)](https://safekit.evidian.com/products/high-availability-software-for-application-clustering/electronic-access-control-software-eacs-redundancy/) * [Building Management System Software (BMS)](https://safekit.evidian.com/products/high-availability-software-for-application-clustering/building-management-system-software-bms-redundancy/) * [SCADA Software](https://safekit.evidian.com/products/high-availability-software-for-application-clustering/scada-software-redundancy-high-availability/) * [Solutions](https://safekit.evidian.com/products/high-availability-software-for-application-clustering/cluster-configuration/) + - * New application (real-time replication and failover) --- * [Windows (mirror.safe)](https://safekit.evidian.com/products/high-availability-software-for-application-clustering/windows-high-availability-software-synchronous-replication-failover/) * [Linux (mirror.safe)](https://safekit.evidian.com/products/high-availability-software-for-application-clustering/linux-high-availability-software-synchronous-replication-failover/) * New application (network load balancing and failover) --- * [Windows (farm.safe)](https://safekit.evidian.com/products/high-availability-software-for-application-clustering/windows-load-balancing-failover/) * [Linux (farm.safe)](https://safekit.evidian.com/products/high-availability-software-for-application-clustering/linux-load-balancing-failover/) - * Full VM or container real-time replication and failover --- * [Hyper-V (hyperv.safe)](https://safekit.evidian.com/products/high-availability-software-for-application-clustering/hyper-v-replication-automatic-failover-load-balancing/) * [KVM (kvm.safe)](https://safekit.evidian.com/products/high-availability-software-for-application-clustering/linux-kvm-high-availability-replication-automatic-failover-load-balancing/) * [Docker (mirror.safe)](https://safekit.evidian.com/products/high-availability-software-for-application-clustering/docker-container-high-availability-cluster-synchronous-replication-failover/) * [Podman (mirror.safe)](https://safekit.evidian.com/products/high-availability-software-for-application-clustering/podman-the-simplest-high-availability-cluster-between-two-redundant-servers/) * [Kubernetes (k3s.safe)](https://safekit.evidian.com/products/high-availability-software-for-application-clustering/kubernetes-k3s-the-simplest-high-availability-cluster-with-synchronous-replication-and-failover-between-two-redundant-servers/) - * Database (real-time replication and failover) --- * [Microsoft SQL Server (sqlserver.safe)](https://safekit.evidian.com/products/high-availability-software-for-application-clustering/sql-server-high-availability-synchronous-replication-failover/) * [PostgreSQL (postgresql.safe)](https://safekit.evidian.com/products/high-availability-software-for-application-clustering/postgresql-high-availability-synchronous-replication-failover/) * [Oracle (oracle.safe)](https://safekit.evidian.com/products/high-availability-software-for-application-clustering/oracle-high-availability-synchronous-replication-failover/) * [MySQL (mysql.safe)](https://safekit.evidian.com/products/high-availability-software-for-application-clustering/mysql-high-availability-synchronous-replication-failover/) * [MariaDB (mysql.safe)](https://safekit.evidian.com/products/high-availability-software-for-application-clustering/mariadb-simplest-high-availability-cluster-synchronous-replication-failover-redundant-servers/) * [Firebird (firebird.safe)](https://safekit.evidian.com/products/high-availability-software-for-application-clustering/firebird-high-availability-synchronous-replication-failover/) * Web (network load balancing and failover) --- * [Apache (apache\_farm.safe)](https://safekit.evidian.com/products/high-availability-software-for-application-clustering/apache-load-balancing-failover-2/) * [Microsoft IIS (iis\_farm.safe)](https://safekit.evidian.com/products/high-availability-software-for-application-clustering/iis-load-balancing-failover/) * [NGINX (farm.safe)](https://safekit.evidian.com/products/high-availability-software-for-application-clustering/nginx-the-simplest-load-balancing-cluster-with-failover/) - * Amazon AWS --- * [AWS (mirror.safe)](https://safekit.evidian.com/products/high-availability-software-for-application-clustering/aws-high-availability-cluster-synchronous-replication-failover/) * [AWS (farm.safe)](https://safekit.evidian.com/products/high-availability-software-for-application-clustering/aws-load-balancing-cluster-failover/) * Google GCP --- * [GCP (mirror.safe)](https://safekit.evidian.com/products/high-availability-software-for-application-clustering/gcp-high-availability-cluster-synchronous-replication-failover/) * [GCP (farm.safe)](https://safekit.evidian.com/products/high-availability-software-for-application-clustering/gcp-load-balancing-cluster-failover/) * Microsoft Azure --- * [Azure (mirror.safe)](https://safekit.evidian.com/products/high-availability-software-for-application-clustering/azure-high-availability-cluster-synchronous-replication-failover/) * [Azure (farm.safe)](https://safekit.evidian.com/products/high-availability-software-for-application-clustering/azure-load-balancing-cluster-failover/) * Other clouds --- * [All cloud solutions](https://safekit.evidian.com/products/high-availability-software-for-application-clustering/cluster-in-cloud-computing-generic-solution-amazon-aws-microsoft-azure-google-gcp-other-clouds/) * [Cloud (mirror.safe)](https://safekit.evidian.com/products/high-availability-software-for-application-clustering/cloud-high-availability-cluster-synchronous-replication-failover/) * [Cloud (farm.safe)](https://safekit.evidian.com/products/high-availability-software-for-application-clustering/cloud-load-balancing-cluster-failover/) - * Physical security (real-time replication and failover) --- * [Milestone XProtect (milestone.safe)](https://safekit.evidian.com/products/high-availability-software-for-application-clustering/milestone-xprotect-corporate-high-availability-synchronous-replication-failover/) * [Nedap (nedap.safe)](https://safekit.evidian.com/products/high-availability-software-for-application-clustering/nedap-high-availability-synchronous-replication-failover/) * [Genetec SQL Server (sqlserver.safe)](https://safekit.evidian.com/products/high-availability-software-for-application-clustering/genetec-sql-server-the-simplest-high-availability-cluster-with-synchronous-replication-and-failover-between-two-redundant-servers/) * [Bosch AMS (hyperv.safe)](https://safekit.evidian.com/products/high-availability-software-for-application-clustering/bosch-ams-the-simplest-high-availability-cluster-between-two-redundant-servers-without-shared-disk/) * [Bosch BIS (hyperv.safe)](https://safekit.evidian.com/products/high-availability-software-for-application-clustering/bosch-bis-the-simplest-high-availability-cluster-between-two-redundant-servers-without-shared-disk/) * [Bosch BVMS (hyperv.safe)](https://safekit.evidian.com/products/high-availability-software-for-application-clustering/bosch-bvms-the-simplest-high-availability-cluster-between-two-redundant-servers-without-shared-disk/) * [Hanwha Vision (hyperv.safe)](https://safekit.evidian.com/products/high-availability-software-for-application-clustering/hanwha-vision-cluster-without-shared-storage-on-a-san/) * [Hanwha Wisenet (hyperv.safe)](https://safekit.evidian.com/products/high-availability-software-for-application-clustering/hanwha-wisenet-wave-the-simplest-high-availability-cluster-between-two-redundant-servers-without-shared-disk/) - * Siemens (real-time replication and failover) --- * [Siemens Siveillance suite (hyperv.safe)](https://safekit.evidian.com/products/high-availability-software-for-application-clustering/siemens-siveillance-redundancy-high-availability-cluster-active-active/) * [Siemens Desigo CC (hyperv.safe)](https://safekit.evidian.com/products/high-availability-software-for-application-clustering/siemens-desigo-cc-redundancy-high-availability-cluster-active-active/) * [Siemens Siveillance VMS (SiveillanceVMS.safe)](https://safekit.evidian.com/products/high-availability-software-for-application-clustering/siemens-siveillance-vms-the-simplest-high-availability-cluster-between-two-redundant-servers/) * [Siemens SiPass (hyperv.safe)](https://safekit.evidian.com/products/high-availability-software-for-application-clustering/siemens-sipass-redundancy-high-availability-cluster-active-active/) * [Siemens SIPORT (hyperv.safe)](https://safekit.evidian.com/products/high-availability-software-for-application-clustering/siemens-siport-redundancy-high-availability-cluster-active-active/) * [Siemens SIMATIC PCS 7 (hyperv.safe)](https://safekit.evidian.com/products/high-availability-software-for-application-clustering/siemens-simatic-pcs-7-redundancy-high-availability-cluster-active-active/) * [Siemens SIMATIC WinCC (hyperv.safe)](https://safekit.evidian.com/products/high-availability-software-for-application-clustering/siemens-simatic-wincc-redundancy-high-availability-cluster-active-active/) * [Architectures](#) + - * Basic architectures --- * [Overview](https://safekit.evidian.com/products/high-availability-software-for-application-clustering/high-availability-architectures/) * [Mirror Cluster](https://safekit.evidian.com/products/high-availability-software-for-application-clustering/file-replication-byte-level-with-failover-mirror-cluster/) * [Farm Cluster](https://safekit.evidian.com/products/high-availability-software-for-application-clustering/network-load-balancing-cluster/) * [SafeKit Console](https://safekit.evidian.com/products/high-availability-software-for-application-clustering/safekit-smart-console-your-high-availability-cluster-in-your-pocket/) - * Advanced architectures --- * [Farm+Mirror Cluster](https://safekit.evidian.com/products/high-availability-software-for-application-clustering/clustering-software-load-balancing-mirroring/) * [Active Active Cluster with Replicaton](https://safekit.evidian.com/products/high-availability-software-for-application-clustering/active-active-cluster-real-time-replication/) * [N-1 Cluster](https://safekit.evidian.com/products/high-availability-software-for-application-clustering/n-1-redundancy/) - * Hypervisor architectures --- * [Hyper-V Cluster](https://safekit.evidian.com/products/high-availability-software-for-application-clustering/hyper-v-replication-automatic-failover-load-balancing/) * [KVM Cluster](https://safekit.evidian.com/products/high-availability-software-for-application-clustering/linux-kvm-high-availability-replication-automatic-failover-load-balancing/) - * Container architectures --- * [Docker Cluster](https://safekit.evidian.com/products/high-availability-software-for-application-clustering/docker-container-high-availability-cluster-synchronous-replication-failover/) * [Podman Cluster](https://safekit.evidian.com/products/high-availability-software-for-application-clustering/podman-the-simplest-high-availability-cluster-between-two-redundant-servers/) * [Best practises](#) + - * High availability best practises --- * [High Availability Architectures & Software Clustering Best Practices](https://safekit.evidian.com/products/high-availability-software-for-application-clustering/high-availability-architectures-and-best-practices/) * [Shared Nothing vs. Shared Disk Architecture: Choosing the Best HA Cluster](https://safekit.evidian.com/products/high-availability-software-for-application-clustering/shared-nothing-architecture-vs-shared-disk-architecture/) * [Software clusering vs hardware clustering](https://safekit.evidian.com/products/high-availability-software-for-application-clustering/clustering-software-vs-hardware-clustering/) * [VM HA vs. Application HA: Choose Your Redundancy Level with SafeKit](https://safekit.evidian.com/products/high-availability-software-for-application-clustering/vm-ha-vs-application-ha/) * [High Availability and Disaster Recovery (HADR)](https://safekit.evidian.com/products/high-availability-software-for-application-clustering/high-availability-disaster-recovery-hadr/) * [HA Cluster vs. Fault Tolerant System: Choosing the Right Redundancy Strategy](https://safekit.evidian.com/products/high-availability-software-for-application-clustering/high-availability-cluster-vs-fault-tolerant-system/) * [How to Implement Redundant Servers with Simple HA Software](https://safekit.evidian.com/products/high-availability-software-for-application-clustering/how-to-implement-redundant-servers-with-a-simple-software-windows-linux/) - * Replication best practises --- * [Data Replication Techniques for High Availability: A Complete Comparison](https://safekit.evidian.com/products/high-availability-software-for-application-clustering/data-replication-techniques/) * [Synchronous vs. Asynchronous Replication: How SafeKit Ensures Zero Data Loss?](https://safekit.evidian.com/products/high-availability-software-for-application-clustering/synchronous-replication-vs-asynchronous-replication/) * [Byte-Level File Replication vs. Block-Level Disk Replication for HA](https://safekit.evidian.com/products/high-availability-software-for-application-clustering/byte-level-file-replication-vs-block-level-disk-replication/) * [Alternative to SQL Server Always On: HA for Express and Standard Editions](https://safekit.evidian.com/products/high-availability-software-for-application-clustering/alternative-always-on-sql-server-express-standard-editions/) - * Clustering best practises --- * [How a Virtual IP Address (VIP) Works in High Availability Clustering?](https://safekit.evidian.com/products/high-availability-software-for-application-clustering/how-a-virtual-ip-address-works/) * [Handling Power Outages and Network Isolation in a HA Cluster](https://safekit.evidian.com/products/high-availability-software-for-application-clustering/power-outage-and-network-isolation-in-a-cluster/) * [Heartbeat, failover and quorum in a cluster](https://safekit.evidian.com/products/high-availability-software-for-application-clustering/heartbeat-failover-quorum-windows-linux-aix-cluster/) * [SAN vs. NAS Shared Storage for Failover Clustering: A Detailed Comparison](https://safekit.evidian.com/products/high-availability-software-for-application-clustering/san-vs-nas-shared-storage-for-a-failover-cluster/) * [What are RPO and RTO? Definitions, Examples, and HA Strategies](https://safekit.evidian.com/products/high-availability-software-for-application-clustering/what-is-rpo-and-rto-with-examples/) * [Microsoft NLB vs SafeKit network load balancing](https://safekit.evidian.com/products/high-availability-software-for-application-clustering/microsoft-nlb-vmware-multicast-unicast-alternative/) * [Resources](#) + - * Free trial --- * [SafeKit free trial](https://safekit.evidian.com/products/high-availability-software-for-application-clustering/safekit-free-trial/) * [One-month license key](https://safekit.evidian.com/products/high-availability-software-for-application-clustering/high-availability-and-load-balancing-cluster-key/) * [Demonstrations](https://safekit.evidian.com/products/high-availability-software-for-application-clustering/high-availability-solutions-ha-solutions-videos/) * [Support](https://safekit.evidian.com/products/high-availability-software-for-application-clustering/safekit-support/) * [Free Training & Certification](https://safekit.evidian.com/products/high-availability-software-for-application-clustering/safekit-on-line-training/) - * Technical documentations --- * [SafeKit quick installation guides](https://safekit.evidian.com/products/high-availability-software-for-application-clustering/safekit-quick-installation-guides/) * [SafeKit user's guide](https://safekit.evidian.com/products/high-availability-software-for-application-clustering/safekit-user-guide-82/) * [SafeKit release notes](https://safekit.evidian.com/products/high-availability-software-for-application-clustering/safekit-release-notes-8-2/) * [SafeKit SRB](https://safekit.evidian.com/wp-content/uploads/downloads_safekit/version-82/82softwarereleasebulletin.pdf) * [Knowledge Base](https://safekit.evidian.com/wp-content/uploads/downloads_safekit/version-82/knowledge-base.pdf) - * Product information --- * [Flyer](https://safekit.evidian.com/wp-content/uploads/documents/high-availability-overview.pdf) * [White Paper - Product](https://safekit.evidian.com/products/high-availability-software-for-application-clustering/high-availability-white-paper/) * [White Paper - High Availability Guide](https://safekit.evidian.com/products/high-availability-software-for-application-clustering/high-availability-guide/) * [Technical Reference for RFI and RFP](https://safekit.evidian.com/products/high-availability-software-for-application-clustering/high-availability-technical-reference-for-rfi-and-rfp-preparation/) * [Support](https://safekit.evidian.com/products/high-availability-software-for-application-clustering/safekit-support/) * [Price](https://safekit.evidian.com/products/high-availability-software-for-application-clustering/get-a-quote-safekit-en/) * [Contact](https://safekit.evidian.com/products/high-availability-software-for-application-clustering/contact-us-for-safekit/) * [![English](https://safekit.evidian.com/wp-content/uploads/flags/us.png)](https://safekit.evidian.com/products/high-availability-software-for-application-clustering/docker-container-high-availability-cluster-synchronous-replication-failover/) [Eviden >](https://eviden.com/) [Products >](https://safekit.evidian.com/products/) [SafeKit: All-in-One SANless High Availability & Application Clustering Software >](https://safekit.evidian.com/) SafeKit: Docker High Availability & Real-Time Data Replication Software # SafeKit: Docker High Availability & Real-Time Data Replication Software ## Stateful Docker Cluster: Synchronous Replication and Failover Without Shared Storage SafeKit offers a lightweight, **"just-enough" HA solution** tailored for organizations that find **Kubernetes** too resource-intensive, complex, or over-engineered for localized or edge-computing container workloads. **SafeKit** provides a streamlined, all-in-one 2-node **high-availability cluster for Docker** on Linux. It serves as a seamless, integrated alternative to the complex "Do It Yourself" (DIY) Linux HA stack—eliminating the technical burden of manually configuring **Corosync** for node membership, **Pacemaker** for resource orchestration, and **DRBD** for block-level replication. By utilizing real-time synchronous replication and an **automatically switched Virtual IP address**, SafeKit creates a robust **SANless cluster** that removes the requirement for expensive shared storage. This architecture ensures transparent client reconnection, rapid automatic failover, and a **zero data loss guarantee (RPO=0)** for containerized applications. * ✅ **Kubernetes Alternative:** High availability for containers without the overhead of K8s networking (Ingress/Load Balancers) and orchestration. * ✅ **Simplified Architecture:** Replaces the Corosync/Pacemaker/DRBD stack with a single software package. * ✅ **No Shared Storage Required:** SANless architecture using local disks and byte-level replication. * ✅ **Automatic Virtual IP (VIP) Failover:** Ensures transparent client reconnection during a switch. * ✅ **Synchronous Data Replication:** Guaranteed zero data loss (RPO=0) between nodes. * ✅ **Automated Failover and Failback:** Rapid application restart on the redundant node without manual scripts. ![SafeKit High Availability Cluster Architecture for Docker providing Virtual IP, Automatic Failover, Automatic Failback, and Real-time replication](https://safekit.evidian.com/wp-content/uploads/2026/02/safekit-docker-5-1024.jpg "A high-availability (HA) solution for Docker containers using SafeKit's SANless architecture.") **A high-availability (HA) solution for Docker containers using SafeKit's SANless architecture.** [⚡ Quick HA installation guide for Docker >](https://safekit.evidian.com/products/high-availability-software-for-application-clustering/docker-container-high-availability-cluster-synchronous-replication-failover/safekit-quick-installation-guide-with-docker/) [🧑 Contact us](https://safekit.evidian.com/products/high-availability-software-for-application-clustering/contact-us-for-safekit/) [🎁 SafeKit free trial](https://safekit.evidian.com/products/high-availability-software-for-application-clustering/safekit-free-trial/) [🏅 Free certification](https://training.my.evidian.com/mod/page/view.php?id=712) [💰 Perpetual license cost](https://safekit.evidian.com/products/high-availability-software-for-application-clustering/get-a-quote-safekit-en/) ## Table of Contents * [How the SafeKit software simply implements a Docker high availability cluster?](#how-safekit-implements-docker-ha) * [How the SafeKit mirror cluster works with Docker?](#safekit-mirror-cluster) * [SafeKit High Availability Limitations](#safekit-ha-limitations) * [Comparison: SafeKit SANless Cluster vs. Traditional Docker HA](#safekit-docker-comparison) * [Comparison: SafeKit vs. Open-Source Linux HA (Pacemaker/Corosync/DRBD)](#safekit-vs-linux-ha-stack) * [Docker High Availability Summary](#docker-ha-summary-quick-installation-guide) * [🔍 SafeKit High Availability Navigation Hub](#hub) ## How the SafeKit software simply implements a Docker high availability cluster? ### How can I achieve high availability for Docker on two servers? **SafeKit** provides a high-availability solution for **Docker** between two redundant servers without requiring a shared disk. The system works by configuring **real-time replication** of directories associated with Docker's persistent data. In the event of a failure, SafeKit manages the automatic failover and restarts your containers on the secondary node in seconds. ### How does automatic network failover work for Docker containers? SafeKit implements an **automatically switched Virtual IP (VIP) address**. This VIP serves as a single entry point for client applications. If the primary server fails, SafeKit moves the Virtual IP to the redundant server using **Gratuitous ARP**. This ensures that clients reconnect transparently to the same IP address where the Docker application has been restarted. ### What is a "SANless" cluster for Docker? A **SANless cluster** for Docker is an architecture that provides high availability without the need for an expensive Storage Area Network (SAN) or Network Attached Storage (NAS). **SafeKit** uses host-based **synchronous replication** to mirror data between the local disks of two servers. This eliminates shared storage as a single point of failure and ensures a **Recovery Point Objective (RPO) of zero**, meaning no data loss occurs during a failover. ### Is it possible to set up a Docker cluster without Kubernetes skills? Yes. This article explains how to [**quickly implement a Docker cluster**](https://safekit.evidian.com/products/high-availability-software-for-application-clustering/docker-container-high-availability-cluster-synchronous-replication-failover/safekit-quick-installation-guide-with-docker/) without specialized clustering skills or complex Kubernetes orchestration. By using SafeKit’s **automatic restart scripts** to handle the start and stop of Docker applications, you get a robust redundancy solution that is much simpler to deploy and maintain than K8s. ### How does SafeKit replication differ from block-level solutions like DRBD for Docker? Unlike most SANless solutions that use **block-level replication** (such as DRBD), **SafeKit** performs **host-based replication at the file level**. This approach is completely transparent for the Docker application because it does not require you to migrate data to a specific, newly created "replicated disk" volume. Instead, you simply configure SafeKit to replicate existing application folders—even those on the **system disk**. This allows you to implement high availability for Docker exactly where it is already installed, without complex disk reconfiguration or application changes. ### Can SafeKit provide high availability for applications beyond Docker? Yes. **SafeKit** is a highly versatile, generic high-availability software compatible with both **Windows and Linux**. Beyond Docker, SafeKit can be used to implement **real-time replication and automatic failover** for any file directory, service, or database. It supports a wide range of technologies, including **Hyper-V and KVM virtual machines**, **Docker**, **K3s**, and various **Cloud applications**. This makes SafeKit a universal clustering solution for protecting critical workloads across diverse IT environments without requiring specialized hardware. ## How the SafeKit mirror cluster works with Docker? ### Step 1. Real-time replication Server 1 (PRIM) runs the Docker application. Clients are connected to a [virtual IP address](https://safekit.evidian.com/products/high-availability-software-for-application-clustering/how-a-virtual-ip-address-works/#mirror). SafeKit replicates in real time modifications made inside files through the network. ![File replication at byte level in a mirror Docker cluster](data:image/svg+xml,%3Csvg%20xmlns='http://www.w3.org/2000/svg'%20viewBox='0%200%20300%20169'%3E%3C/svg%3E)![File replication at byte level in a mirror Docker cluster](https://safekit.evidian.com/wp-content/uploads/2023/02/safekit-prim-second-300.png) The replication is [synchronous](https://safekit.evidian.com/products/high-availability-software-for-application-clustering/synchronous-replication-vs-asynchronous-replication/) 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 Docker 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 of Docker in a mirror cluster](data:image/svg+xml,%3Csvg%20xmlns='http://www.w3.org/2000/svg'%20viewBox='0%200%20300%20169'%3E%3C/svg%3E)![Failover of Docker in a mirror cluster](https://safekit.evidian.com/wp-content/uploads/2023/02/safekit-stop-alone-300.png) 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 Docker cluster](data:image/svg+xml,%3Csvg%20xmlns='http://www.w3.org/2000/svg'%20viewBox='0%200%20300%20169'%3E%3C/svg%3E)![Failback in a mirror Docker cluster](https://safekit.evidian.com/wp-content/uploads/2023/02/safekit-resynchro-alone-300.png) Failback takes place without disturbing the Docker 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 Docker application running on Server 2 and SafeKit replicating file updates to Server 1. ![Return to normal operation in a mirror Docker cluster](data:image/svg+xml,%3Csvg%20xmlns='http://www.w3.org/2000/svg'%20viewBox='0%200%20300%20169'%3E%3C/svg%3E)![Return to normal operation in a mirror Docker cluster](https://safekit.evidian.com/wp-content/uploads/2023/02/safekit-second-prim-300.png) If the administrator wishes the application to run on Server 1, this can be done manually through the web console at an appropriate time, or automatically through configuration. ### How to configure a SafeKit Mirror Cluster for Docker? ![SafeKit Web Console: High Availability configuration dashboard for Docker showing heartbeat networks, virtual IP setup, and real-time directory replication for a mirror cluster.](data:image/svg+xml,%3Csvg%20xmlns='http://www.w3.org/2000/svg'%20viewBox='0%200%20763%20497'%3E%3C/svg%3E)![SafeKit Web Console: High Availability configuration dashboard for Docker showing heartbeat networks, virtual IP setup, and real-time directory replication for a mirror cluster.](https://safekit.evidian.com/wp-content/uploads/2026/01/safekit-mirror-cluster-config.png) The **SafeKit web console** provides an intuitive interface to orchestrate high availability for your critical applications. In just a few steps, you can configure a **SafeKit mirror cluster** to ensure business continuity: * **Application Failover (Macros Tab):** Define the specific application services to be automatically restarted in the event of a failure. * **Heartbeat network(s):** Dedicated communication path(s) used by cluster nodes to continuously monitor each other's health and availability and synchronize failover decisions. * **Virtual IP Management:** Set up the Virtual IP (VIP) for transparent client reconnection after a failover. * **Real-Time Replication:** Select the critical directories for host-based, synchronous byte-level replication. * **Checkers:** Monitor the application's health and trigger automatic recovery if a process failure is detected. The SafeKit cluster includes a dedicated split-brain checker to resolve network isolation issues without the need for a third witness machine or an additional heartbeat network. Learn more about [heartbeat, failover and quorum in a cluster](https://safekit.evidian.com/products/high-availability-software-for-application-clustering/heartbeat-failover-quorum-windows-linux-aix-cluster/). ### How to monitor a SafeKit mirror cluster for Docker? ![SafeKit Web Console: Real-time monitoring of a 2-node mirror cluster for Docker showing PRIM and SECOND states with active data replication.](data:image/svg+xml,%3Csvg%20xmlns='http://www.w3.org/2000/svg'%20viewBox='0%200%20604%20412'%3E%3C/svg%3E)![SafeKit Web Console: Real-time monitoring of a 2-node mirror cluster for Docker showing PRIM and SECOND states with active data replication.](https://safekit.evidian.com/wp-content/uploads/2026/05/mirror-monitoring-prim-second.png) The **SafeKit management console** offers a unified view of your high availability infrastructure. It allows administrators to monitor the **operational state** of the cluster and track data synchronization in real-time. For a 2-node mirror cluster, the console clearly displays the roles of each server: * **PRIM (Primary):** The active node currently running the application and managing the Virtual IP. It performs writes to the local storage and real-time replication to the secondary node. * **SECOND (Secondary):** The standby node receiving synchronous byte-level updates. It is ready to take over instantly if the Primary fails. * **ALONE State:** Visually alerts you when the cluster is running on a single node (e.g., during maintenance or after a failure), indicating that redundancy is temporarily lost. * **Resynchronization Progress:** When a failed node recovers, its status turns orange during background data reintegration, ensuring no downtime during the "return to normal" phase. Beyond simple status icons, the interface provides **one-click failover orchestration**, allowing you to manually reassign the primary role for planned maintenance while ensuring continuous availability for user activity. ## SafeKit High Availability Limitations ### Why a replication of a few Tera-bytes? Resynchronization time after a failure ([step 3](https://safekit.evidian.com/products/high-availability-software-for-application-clustering/file-replication-byte-level-with-failover-mirror-cluster/#mirrorcluster)) * 1 Gb/s network ≈ 3 Hours for 1 Tera-bytes. * 10 Gb/s network ≈ 1 Hour for 1 Tera-bytes or less depending on disk write performances. #### Alternative * For a large volume of data, use [external shared storage](https://safekit.evidian.com/products/high-availability-software-for-application-clustering/san-vs-nas-shared-storage-for-a-failover-cluster/). * More expensive, more complex. ### Why a replication < 1,000,000 files? * Resynchronization time performance after a failure ([step 3](https://safekit.evidian.com/products/high-availability-software-for-application-clustering/file-replication-byte-level-with-failover-mirror-cluster/#mirrorcluster)). * Time to check each file between both nodes. #### Alternative * Put the many files to replicate in a virtual hard disk / virtual machine. * Only the files representing the virtual hard disk / virtual machine will be replicated and resynchronized in this case. ### Why a failover ≤ 32 replicated VMs? * Each VM runs in an independent mirror module. * Maximum of 32 mirror modules running on the same cluster. #### Alternative * Use an external shared storage and another VM clustering solution. * More expensive, more complex. ### Why a LAN/VLAN network between remote sites? * Automatic failover of the [virtual IP address](https://safekit.evidian.com/products/high-availability-software-for-application-clustering/how-a-virtual-ip-address-works/) with 2 nodes in the same subnet. * Good bandwidth for resynchronization ([step 3](https://safekit.evidian.com/products/high-availability-software-for-application-clustering/file-replication-byte-level-with-failover-mirror-cluster/#mirrorcluster)) and good latency for [synchronous replication](https://safekit.evidian.com/products/high-availability-software-for-application-clustering/synchronous-replication-vs-asynchronous-replication/) (typically a round-trip of less than 2ms). #### Alternative * Use a [load balancer for the virtual IP address](https://safekit.evidian.com/products/high-availability-software-for-application-clustering/how-a-virtual-ip-address-works/) if the 2 nodes are in 2 subnets (supported by SafeKit, especially in the cloud). * Use backup solutions with asynchronous replication for high latency network. ## Comparison: SafeKit SANless Cluster vs. Traditional Docker HA | Feature | Traditional HA (K8s / Shared Storage) | SafeKit (SANless Mirror) | | --- | --- | --- | | Storage Architecture | Requires expensive **SAN or NAS** (Shared Disk) | **Shared-Nothing**: Uses local disks only | | Replication Type | Often Block-level (Complex to configure) | **Byte-level File Replication** (Transparent) | | Data Consistency | Depends on external storage reliability | **Synchronous Replication** (RPO = 0) | | Network Setup | Complex (Load balancers, Ingress, etc.) | **Automatic Virtual IP (VIP)** failover | | Skill Requirement | Expert (Kubernetes/Clustering specialists) | **Simple**: No specialized skills required | | Failback Process | Manual or complex re-syncing | **Automatic Resynchronization** of modified data | ## Comparison: SafeKit vs. Open-Source Linux HA (Pacemaker/Corosync/DRBD) | Feature | Linux HA Stack (Pacemaker + Corosync + DRBD) | SafeKit (SANless Mirror) | | --- | --- | --- | | Architecture | **Modular:** Requires managing 3+ distinct tools and kernel modules. | **All-in-One:** Single integrated software for replication and failover. | | Replication Level | **Block-level (DRBD):** Replicates the entire partition/disk volume. | **Byte-level (SafeKit):** Replicates only modified data inside specific files. | | Ease of Configuration | **Complex:** Requires CLI (Command Line Interface) expertise to manually program ordering constraints (Virtual IP, mounts), application recovery scripts, and quorum/fencing rules. | **Simple:** Intuitive web console and ready-to-use application modules. | | Fencing (STONITH) | **Mandatory to prevent corruption:** STONITH (Shoot The Other Node In The Head) requires a specialized hardware (IPMI/iDRAC) to literally cut the power or reboot the failing server. | **Software-based:** [Intelligent split-brain resolution without extra hardware.](https://safekit.evidian.com/products/high-availability-software-for-application-clustering/heartbeat-failover-quorum-windows-linux-aix-cluster/) | | Failback Process | **Manual/Technical:** Risk of data divergence or "split-brain" during re-sync. | **Automatic & Transparent:** Background resynchronization with safe failback. | | Maintenance | Requires high specialized skills to update/troubleshoot individual components. | Easy to maintain by general system administrators via web dashboard. | ## Docker High Availability Summary **SafeKit** provides a simple **2-node HA cluster for Docker**, offering a lightweight **Kubernetes alternative** for mission-critical workloads. By replacing the complex **Corosync, Pacemaker, and DRBD** stack, SafeKit eliminates the need for expensive **SAN/NAS** shared storage. Through **real-time synchronous replication** and an **automatic Virtual IP (VIP) failover**, SafeKit ensures **zero data loss (RPO=0)** and transparent application recovery. It is the ideal solution for organizations requiring robust, **SANless high availability** with minimal configuration and administrative overhead. ## 🔍 SafeKit High Availability Navigation Hub Explore SafeKit: Features, technical videos, documentation, and free trial | Resource Type | Description | Direct Link | | --- | --- | --- | | **Key Features** | Why Choose SafeKit for Simple and Cost-Effective High Availability? | [See Why Choose SafeKit for High Availability](https://safekit.evidian.com/products/high-availability-software-for-application-clustering/#why-choose-safekit-for-ha "Discover SafeKit features for simple and cost-effective high availability") | | **Use Cases** | Explore How SafeKit Ensures the High Availability of Critical Infrastructure | [See All Use Cases](https://safekit.evidian.com/products/high-availability-software-for-application-clustering/#safekit-use-cases "Explore SafeKit high availability use cases") | | **Deployment Model** | All-in-One SANless HA: Shared-Nothing Software Clustering | [See SafeKit All-in-One SANless HA](https://safekit.evidian.com/products/high-availability-software-for-application-clustering/#all-in-one-sanless-ha "Learn about all-in-one SANless high availability with shared-nothing software clustering") | | **HA Strategies** | SafeKit: Infrastructure (VM) vs. Application-Level High Availability | [See SafeKit HA & Redundancy: VM vs. Application Level](https://safekit.evidian.com/products/high-availability-software-for-application-clustering/#safekit-ha-redundancy-choices "Compare VM-level redundancy with SafeKit application-level high availability strategies") | | **Technical Specifications** | Technical Limitations for SafeKit Clustering | [See SafeKit High Availability Limitations](https://safekit.evidian.com/products/high-availability-software-for-application-clustering/#safekit-ha-limitations "Technical requirements and limitations for SafeKit application clustering") | | **Proof of Concept** | SafeKit: High Availability Configuration & Failover Demos | [See SafeKit Failover Tutorials](https://safekit.evidian.com/products/high-availability-software-for-application-clustering/#safekit-failover-tutorials "Step-by-step videos on SafeKit high availability, from installation to automated failover") | | **Architecture** | How the SafeKit Mirror Cluster works (Real-Time Replication & Failover) | [See SafeKit Mirror Cluster: Real-Time Replication & Failover](https://safekit.evidian.com/products/high-availability-software-for-application-clustering/#safekit-mirror-cluster "See technical architecture and failover mechanism of SafeKit Mirror Cluster") | | **Architecture** | How the SafeKit Farm Cluster works (Network Load Balancing & Failover) | [See SafeKit Farm Cluster: Network Load Balancing & Failover](https://safekit.evidian.com/products/high-availability-software-for-application-clustering/#safekit-farm-cluster "Technical overview of SafeKit Farm Cluster architecture with network load balancing") | | **Competitive Advantages** | Comparison: SafeKit vs. Traditional High Availability (HA) Clusters | [See SafeKit vs. Traditional HA Cluster Comparison](https://safekit.evidian.com/products/high-availability-software-for-application-clustering/#safekit-ha-comparison "Detailed comparison of SafeKit software vs traditional hardware-based HA clusters") | | **Technical Resources** | SafeKit High Availability: Documentation, Downloads & Trial | [See SafeKit HA Free Trial & Technical Documentation](https://safekit.evidian.com/products/high-availability-software-for-application-clustering/#safekit-ha-technical-resources "Access SafeKit free trial, technical documentation, and high availability white papers") | | **Pre-configured Solutions** | SafeKit Application Module Library: Ready-to-Use HA Solutions | [See SafeKit High Availability Application Modules](https://safekit.evidian.com/products/high-availability-software-for-application-clustering/#safekit-ha-application-modules "Browse the library of pre-configured SafeKit modules for automated application failover") | [🧑 Contact us](https://safekit.evidian.com/products/high-availability-software-for-application-clustering/contact-us-for-safekit/) [🎁 SafeKit free trial](https://safekit.evidian.com/products/high-availability-software-for-application-clustering/safekit-free-trial/) [🏅 Free certification](https://training.my.evidian.com/mod/page/view.php?id=712) [💰 Perpetual license cost](https://safekit.evidian.com/products/high-availability-software-for-application-clustering/get-a-quote-safekit-en/) * © Eviden, all rights reserved * |[Eviden privacy](https://eviden.com/privacy-policy) * |[Eviden terms and conditions](https://eviden.com/terms-and-conditions) * |[Eviden](https://eviden.com) [![eviden-logo](https://safekit.evidian.com/wp-content/uploads/2026/01/eviden-logo-black-265-54.png)](https://eviden.com/) We use cookies on our website to give you the most relevant experience by remembering your preferences and repeat visits. By clicking “Accept”, you consent to the use of ALL the cookies. However you may visit Cookie Settings to provide a controlled consent.