---
canonical: https://safekit.evidian.com/
part 1 of 3
topics: What is SafeKit?, 🔍 SafeKit High Availability Navigation Hub,  Why Choose SafeKit for Simple and Cost-Effective High Availability?, SafeKit Use Cases, Why an All-in-One SANless High Availability Product is Essential?,  Choosing Your High Availability Strategy: VM HA vs. Application HA, SafeKit High Availability Limitations, SafeKit Technical Failover Tutorials & Demos, How the SafeKit mirror cluster works?, How the SafeKit farm cluster works?
---

# SafeKit: All-in-One SANless High Availability & Application Clustering Software



## What is SafeKit?

**SafeKit** is an **all-in-one high availability software** solution that ensures 100% application uptime by combining real-time **host-based replication**, automatic **failover**, and **load balancing** into a single package.

By synchronizing data between standard servers, **SafeKit** eliminates the need for expensive shared storage (SAN) or specialized IT skills, providing a simple, cost-effective way to protect **enterprise databases** (like SQL Server), **critical security systems** (like Milestone XProtect Video Management Software), and **SCADA industrial control software** (like Siemens applications) across both Windows and Linux environments.

![Evidian SafeKit official logo - SANless high availability and application clustering software icon](https://safekit.evidian.com/wp-content/uploads/2026/04/safekit-icon-512x512-1.png "Evidian SafeKit Icon")

[🧑 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/)

## 🔍 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") |

## Why Choose SafeKit for Simple and Cost-Effective High Availability?

### What are SafeKit’s features?

SafeKit provides the following features for Windows and Linux in a single software product:

* **Load balancing**
* **Synchronous real-time file replication**
* **Automatic application failover**
* **Automatic failback after a server failure**

### Do I need special skills to set up SafeKit?

No. SafeKit is simple to deploy—no advanced expertise required.

### Does SafeKit require additional hardware?

No. SafeKit runs on your existing servers, virtual machines, or in the cloud—no shared disks or SAN storage needed.

### Are extra software licenses required for SafeKit?

No. SafeKit works with standard Windows and Linux editions and does not need enterprise database licenses.

### What problems does SafeKit solve?

SafeKit solves:

* Hardware failures (20% of problems), including the complete failure of a computer room
* Software failures (40% of problems), including restart of critical processes
* Human errors (40% of problems) thanks to its ease of use

### Which applications are supported by SafeKit?

You can implement real-time replication and failover for:

* All types of applications, file directories, and services
* Databases
* Complete Hyper-V or KVM virtual machines
* Docker, Podman, and cloud applications

### How does SafeKit cut costs?

SafeKit eliminates the following requirements:

* Network load balancers or dedicated proxy servers
* Shared disks or replicated SAN storage
* Enterprise editions of operating systems and databases
* Specialized cluster maintenance skills

### How is SafeKit High Availability priced and licensed?

**SafeKit** features a transparent, cost-effective **per-node licensing model** based strictly on the number of servers, regardless of CPU cores or sockets. Unlike many high-availability competitors that mandate recurring subscriptions, SafeKit offers **perpetual licenses** to ensure a lower Total Cost of Ownership (TCO) and long-term software assets.

* **No Hidden Costs:** All [pre-configured HA application modules](https://safekit.evidian.com/products/high-availability-software-for-application-clustering/#safekit-ha-application-modules "Explore free SafeKit HA application modules") are provided free of charge.
* **Risk-Free Evaluation:** Download a [30-day free trial](https://safekit.evidian.com/products/high-availability-software-for-application-clustering/#safekit-ha-technical-resources "Download SafeKit 30-day free trial") to test failover and replication in your environment.
* **Customized Quotes:** Please **[contact us for a quote](https://safekit.evidian.com/products/high-availability-software-for-application-clustering/get-a-quote-safekit-en/ "Request a customized SafeKit pricing quote")** tailored to your specific high availability requirements.

## SafeKit Use Cases

### SafeKit for OEM

Offering high availability with your application increases business value by ensuring continuous service, reducing downtime risks, and enhancing customer trust, while enabling critical operations to run without interruption on standard infrastructures.

![SafeKit for OEM](data:image/svg+xml,%3Csvg%20xmlns='http://www.w3.org/2000/svg'%20viewBox='0%200%20512%20512'%3E%3C/svg%3E)![SafeKit for OEM](https://safekit.evidian.com/wp-content/uploads/2026/05/safekit-for-oem-512-512.jpg)

Add SafeKit in your catalog as a high availability option: a software-only solution tailored to your application, with no hidden costs such as shared storage, fully hardware-agnostic, and deployable on physical, virtual, or cloud environments, with simple plug-and-play administration.

### SafeKit for Edge

Edge sites often have no data center and no HA expertise—yet business continuity is critical. SafeKit keeps edge applications running in factories, oil platforms, ships, building security, air traffic control, 5G networks, healthcare, retail...

![SafeKit for Edge](data:image/svg+xml,%3Csvg%20xmlns='http://www.w3.org/2000/svg'%20viewBox='0%200%20512%20512'%3E%3C/svg%3E)![SafeKit for Edge](https://safekit.evidian.com/wp-content/uploads/2026/05/safekit-edge-512-512.jpg)

SafeKit turns two standard edge servers (any brand) into a plug‑and‑play HA cluster—no shared storage/SAN. One lightweight stack delivers real‑time replication and automatic failover (and can also include load balancing), easy to install and administer.

### SafeKit for VMS

Video Management Software (VMS) is critical to public safety, recording and displaying live and archived video so security officers can react instantly to incidents. Any VMS outage directly puts people and assets at risk.

![SafeKit for VMS](data:image/svg+xml,%3Csvg%20xmlns='http://www.w3.org/2000/svg'%20viewBox='0%200%20512%20512'%3E%3C/svg%3E)![SafeKit for VMS](https://safekit.evidian.com/wp-content/uploads/2026/05/safekit-vms-512-512.jpg)

SafeKit prevents video loss and monitoring gaps by maintaining continuous access to live and recorded streams, even during server or software failures. It integrates seamlessly with leading VMS platforms such as **Milestone, Genetec, Hanwha**, and others to keep surveillance operational when it matters most.

### SafeKit for EACS

Electronic Access Control Systems (EACS) are essential to physical security, controlling and monitoring access to private and sensitive areas through doors, badges, readers, and sensors. Any system outage can immediately expose people, buildings, and assets to intrusion.

![SafeKit for EACS](data:image/svg+xml,%3Csvg%20xmlns='http://www.w3.org/2000/svg'%20viewBox='0%200%20512%20512'%3E%3C/svg%3E)![SafeKit for EACS](https://safekit.evidian.com/wp-content/uploads/2026/05/safekit-eacs-512-512.jpg)

SafeKit keeps access control decisions, alarms, and credentials available at all times by eliminating single points of failure. It delivers resilient operation for EACS solutions such as **Hirsch Microsesame, Nedap AEOS, and Siemens SiPass**, ensuring secure access even during infrastructure incidents.

### SafeKit for SCADA

SCADA (Supervisory Control and Data Acquisition) systems are at the core of industrial environments, enabling operators to monitor and control critical processes through sensors, valves, pumps, motors, and human‑machine interfaces.

![SafeKit for SCADA](data:image/svg+xml,%3Csvg%20xmlns='http://www.w3.org/2000/svg'%20viewBox='0%200%20512%20512'%3E%3C/svg%3E)![SafeKit for SCADA](https://safekit.evidian.com/wp-content/uploads/2026/05/safekit-scada-512-512.jpg)

SafeKit minimizes production downtime by ensuring SCADA control systems—such as those powering **Probat coffee roasters and ALSTEF baggage sorting machines**—remain operational despite hardware or software incidents. This allows operators to retain full visibility and control of industrial processes at all times, preventing costly shutdowns and safety risks.

### SafeKit for BMS

Building Management Systems (BMS) are central to modern buildings, providing automated control of HVAC, electrical distribution, lighting, fire safety, and water systems. Any system outage can directly impact occupant safety, comfort, and building operations.

![SafeKit for BMS](data:image/svg+xml,%3Csvg%20xmlns='http://www.w3.org/2000/svg'%20viewBox='0%200%20512%20512'%3E%3C/svg%3E)![SafeKit for BMS](https://safekit.evidian.com/wp-content/uploads/2026/05/safekit-bms-512-512.jpg)

SafeKit safeguards building automation by allowing BMS services to continue running transparently in the event of a failure. It supports platforms such as **Siemens Desigo CC, Bosch BIS**, and related systems to maintain safe, efficient, and uninterrupted building operations.

### SafeKit for ATC

Air Traffic Control (ATC) systems are critical to aviation safety, enabling real‑time monitoring and control of aircraft movements on the ground and in the air through surveillance, guidance, and control applications.

![SafeKit for ATC](data:image/svg+xml,%3Csvg%20xmlns='http://www.w3.org/2000/svg'%20viewBox='0%200%20512%20512'%3E%3C/svg%3E)![SafeKit for ATC](https://safekit.evidian.com/wp-content/uploads/2026/05/safekit-atc-512-512.jpg)

SafeKit reinforces ATC system resilience by guaranteeing uninterrupted controller access to critical airside applications. It is used with ATC and airport solutions such as **ADB SafeGate** to support safe, continuous air traffic operations under all conditions.

### SafeKit for OCC

Operations Control Centers (OCC) are at the heart of modern metro networks, centralizing supervision of train movements, power supply, signaling, passenger information, and incident management. In automated driverless metro lines, the OCC is the single point of control for operations.

![SafeKit for OCC](data:image/svg+xml,%3Csvg%20xmlns='http://www.w3.org/2000/svg'%20viewBox='0%200%20512%20512'%3E%3C/svg%3E)![SafeKit for OCC](https://safekit.evidian.com/wp-content/uploads/2026/05/safekit-occ-512-512.jpg)

SafeKit secures uninterrupted metro supervision by ensuring OCC applications remain available during failures. It supports Operations Control Centers for **automated, driverless Paris metro lines**, enabling continuous service and rapid incident response without reliance on onboard drivers.

## Why an All-in-One SANless High Availability Product is Essential?

In the world of business continuity, many organizations mistakenly believe that having a backup or a data replication tool is the same as having **High Availability (HA)**. In reality, these are only pieces of a much larger puzzle. To truly guarantee 100% uptime, you need an all-in-one solution that integrates every layer of the failover process.

Here is why a fragmented approach fails and why an integrated, all-in-one product like **SafeKit**—utilizing **host-based replication at the file level**—is required.

### Is host-based replication alone sufficient for High Availability?

No. Data replication is simply the act of copying data from Server A to Server B. While critical, replication by itself does not provide availability. Without the other components of an HA stack, replication is just a "passive copy" that requires manual, time-consuming intervention to become useful:

* If Server A crashes, data replication software will not automatically point your users to Server B.
* It will not detect that the application has stopped.
* It will not restart the services.

### The Hidden Risks of Fragmented Solutions: Why Siloed HA Increases Failure

Many vendors require you to "bolt together" several different products to achieve **host-based replication**, **failover**, and **load balancing**. This fragmented architecture is a dangerous strategy for mission-critical systems:

* **Fragile Integration:** When you use product A for replication and product B for clustering, you create a "house of cards." Every OS update or security patch risks breaking the fragile communication link between these separate engines.
* **High Cognitive Load & Human Error:** Managing multiple interfaces increases the risk of mistakes. During a high-pressure system failure, jumping between different GUIs or using different CLI syntaxes to diagnose a problem leads to confusion and extended downtime.
* **Vendor Finger-Pointing:** If a failover fails, the replication vendor may blame the clustering tool, leaving you stuck in the middle with no clear path to resolution. An all-in-one solution provides a single point of accountability.
* **Complex Maintenance:** Fragmented systems require specialized skills for each separate component, making the solution harder to maintain and significantly more expensive over time.

### Beyond data, what specific components are required for a true SANless failover?

To automate recovery and eliminate downtime, an all-in-one product must manage several technical moving parts simultaneously:

* **Host-Based Replication:** real-time, synchronous replication of critical application data between servers without relying on shared storage (SAN). This ensures zero data loss (RPO=0) and eliminates expensive hardware dependencies.
* **Virtual IP Address (VIP):** This provides a single entry point for users. When a failure occurs, the software moves the VIP from the failed node to the healthy one, so users don't have to change their configuration.
* **Hardware and Software Error Detectors:** The system must constantly "heartbeat" both the physical server and the specific software processes to identify a hang or a crash immediately.
* **Customizable Restart Scripts:** Not every application starts the same way. An all-in-one tool allows for custom scripts to ensure complex services start in the correct order.
* **Automatic Failover:** The intelligence to orchestrate the entire move from one server to another without human input.

### Why must the failover mechanism be synchronized with host-based replication?

If your failover manager and your data replication are two different products, they may not be "in sync."

**The Danger:** If a failover occurs but the replication hasn't finished sending the latest bits, Server B will start the application with outdated or corrupted data.

An **all-in-one SANless HA solution** ensures that the failover mechanism is aware of the replication state. It will only allow the application to start on the backup node if the data is guaranteed to be up-to-date, preventing conflicting active nodes and data loss.

### What happens when the failed server is repaired (failback)?

Often ignored in technical guides and poorly executed by traditional HA solutions, automatic failback remains the most critical requirement for true resilience. A true all-in-one product handles the "Return to Normal" as elegantly as the failure. When the failed server comes back online, it is behind in data. The HA software must:

1. **Resynchronize data** in the background from the active node to the recovered node.
2. **Maintain Uptime:** This resynchronization must happen without interrupting the application currently running on the active node.
3. **Restore Redundancy:** Once the data is mirrored again, the cluster automatically returns to a protected state, ready for the next event.

### Block vs. File Level Replication: Why Transparency Matters

The technical method used for **host-based replication** significantly impacts how much you have to change your existing application setup.

* **The Challenge of Block-Level Replication:** Most SANless solutions replicate at the disk/block level. This is **not transparent** for the application. It requires you to reconfigure the application entirely to move its data onto a specific, newly created "replicated disk" volume. This often involves complex migration and potential changes to application logic.
* **The SafeKit File-Level Advantage:** SafeKit performs **host-based replication at the file level**, which is completely transparent for the application. You do not need to move data to a special disk; you simply configure SafeKit to replicate the existing application folders. These folders can even remain on the **system disk**, allowing you to protect an application exactly where it is already installed.

## Choosing Your High Availability Strategy: VM HA vs. Application HA

SafeKit offers two primary approaches to ensure business continuity: Virtual Machine HA (VM HA) and Application HA. While both methods provide automatic failover capabilities, they differ significantly in their scope, data replication mechanisms, recovery speed, and platform compatibility. This comparison breaks down these differences to help identify the optimal strategy for specific IT environments, whether the focus is on broad virtualization support or granular, high-speed application recovery.

Feature Comparison: SafeKit VM HA vs. SafeKit Application HA Clustering

| Comparison Feature | VM HA with SafeKit Hyper-V or KVM Module | Application HA with SafeKit Application Modules |
| --- | --- | --- |
| Deployment Diagram | Diagram illustrating SafeKit VM High Availability using Hyper-V or KVM: two hypervisors replicate the entire VM image, enabling full VM reboot and recovery upon host failure.Diagram illustrating SafeKit VM High Availability using Hyper-V or KVM: two hypervisors replicate the entire VM image, enabling full VM reboot and recovery upon host failure. | Diagram illustrating SafeKit Application High Availability: two application servers (nodes) with file system replication and quick application-level failover for low RTO.Diagram illustrating SafeKit Application High Availability: two application servers (nodes) with file system replication and quick application-level failover for low RTO. |
| Failover Scope | SafeKit inside 2 hypervisors: replication and failover of the full VM. | SafeKit inside 2 virtual or physical machines: replication and failover at the application level. |
| Data Replicated | Replicates more data (Application + Operating System). | Replicates only application data, leading to smaller data volumes. |
| Recovery Process & Speed (RTO) | Reboot of VM on hypervisor 2 if hypervisor 1 crashes. Recovery time depends on the OS reboot. VM checker and failover mechanism. | Quick recovery time with restart of App on OS2 if server 1 crashes. Typically around 1 minute or less (low RTO). Application checker and software failover. |
| Installation | Application is installed once in a single VM. | Application is installed on two nodes. |
| Configuration | Generic solution for any application / OS running in the VM.  * It does not require a technical understanding of the application installed within the VM. * It is the best solution if you do not know how the application works. * You only need to define the location of the VM files. | It requires a technical understanding of the application itself.  * Which services need to be restarted. * The specific application folders that need real-time replication. * The configuration of a virtual IP address for failover. |
| Platform Compatibility | Works with Windows/Hyper-V and Linux/KVM but is not compatible with VMware. | Platform agnostic; works with physical or virtual machines, cloud infrastructure, and any hypervisor, including VMware. |
| Ideal For | Ideal for managing complex environments with multiple applications across several VMs through a single HA policy. | Ideal for embedding high availability directly into a software solution, independent of the underlying hardware or hypervisor. |

## 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.

## SafeKit Technical Failover Tutorials & Demos

### [SafeKit Video: Webinar (9:43)](https://www.youtube.com/embed/UiLwzqsMxis?rel=0&autoplay=1&cc_load_policy=1&hl=en&cc_lang_pref=en)

#### Chapters

1. [Introduction](https://www.youtube.com/embed/UiLwzqsMxis?rel=0&autoplay=1&cc_load_policy=1&hl=en&cc_lang_pref=en&start=0&end=38) (0:38)
2. [Demonstration of SafeKit](https://www.youtube.com/embed/UiLwzqsMxis?rel=0&autoplay=1&cc_load_policy=1&hl=en&cc_lang_pref=en&start=38&end=139) (1:41)
3. [Examples of redundancy and high availability solution](https://www.youtube.com/embed/UiLwzqsMxis?rel=0&autoplay=1&cc_load_policy=1&hl=en&cc_lang_pref=en&start=139&end=259) (2:00)
4. [SafeKit sold in many different countries with Milestone](https://www.youtube.com/embed/UiLwzqsMxis?rel=0&autoplay=1&cc_load_policy=1&hl=en&cc_lang_pref=en&start=259&end=308) (0:49)
5. [Choose between 2 solutions: virtual machine or application cluster](https://www.youtube.com/embed/UiLwzqsMxis?rel=0&autoplay=1&cc_load_policy=1&hl=en&cc_lang_pref=en&start=308&end=457) (2:29)
6. [Distinctive advantages](https://www.youtube.com/embed/UiLwzqsMxis?rel=0&autoplay=1&cc_load_policy=1&hl=en&cc_lang_pref=en&start=457) (2:06)

[All videos here](https://safekit.evidian.com/products/high-availability-software-for-application-clustering/safekit-on-line-training/)

### [SafeKit: How to Implement HADR (7:40)](https://www.youtube.com/watch?v=g5zcTjiY7T4)

#### Chapters

1. [Introduction to SafeKit HADR over Stretched VLANs](https://www.youtube.com/embed/g5zcTjiY7T4?autoplay=1&start=0&end=65) (1:06)
2. [How Synchronous Mirroring & Double-Acknowledgment Works (1:41)](https://www.youtube.com/embed/g5zcTjiY7T4?autoplay=1&start=65&end=166)
3. [Failover Mechanics: Gratuitous ARP (GARP) & Virtual IP](https://www.youtube.com/embed/g5zcTjiY7T4?autoplay=1&start=166&end=296) (2:10)
4. [Designing for Slow WAN: HA vs. Backup Strategies](https://www.youtube.com/embed/g5zcTjiY7T4?autoplay=1&start=296) (2:45)

[Learn more about SafeKit HADR](https://safekit.evidian.com/products/high-availability-software-for-application-clustering/high-availability-disaster-recovery-hadr/)

### [SafeKit Video: Virtual Machine-Level Clustering (5:15)](https://www.youtube.com/embed/foo6YKg5Dmw?rel=0&autoplay=1)

#### Chapters

1. [2 Hyper-V nodes and 2 virtual machines](https://www.youtube.com/embed/foo6YKg5Dmw?rel=0&autoplay=1&start=0&end=49) (0:49)
2. [Configure the cluster and two hyperv.safe modules](https://www.youtube.com/embed/foo6YKg5Dmw?rel=0&autoplay=1&start=49&end=168) (1:59)
3. [Start and test VM replication, migration, failover on crash](https://www.youtube.com/embed/foo6YKg5Dmw?rel=0&autoplay=1&start=168) (2:26)

[Free trial here](https://safekit.evidian.com/products/high-availability-software-for-application-clustering/hyper-v-replication-automatic-failover-load-balancing/safekit-quick-installation-guide-with-hyper-v/)

### [SafeKit Video: Application-Level Clustering with SQL (8:47)](https://www.youtube.com/embed/T_6PsS4f9OQ?rel=0&autoplay=1)

#### Chapters

1. [2 nodes with SQL Server](https://www.youtube.com/embed/T_6PsS4f9OQ?rel=0&autoplay=1&start=0&end=32) (0:32)
2. [Configure the cluster and the mirror.safe module](https://www.youtube.com/embed/T_6PsS4f9OQ?rel=0&autoplay=1&start=32&end=270) (3:58)
3. [Start and test SQL replication, migration, failover on crash](https://www.youtube.com/embed/T_6PsS4f9OQ?rel=0&autoplay=1&start=270) (4:17)

[Free trial here](https://safekit.evidian.com/products/high-availability-software-for-application-clustering/windows-high-availability-software-synchronous-replication-failover/safekit-quick-installation-guide-for-a-new-windows-application-with-real-time-replication-and-failover/)

### [SafeKit Video: OEM High Availability Integration (4:22)](https://www.youtube.com/embed/dxiPG5ILC-0?rel=0&autoplay=1)

#### Chapters

1. [SafeKit for OEM Integration](https://www.youtube.com/embed/dxiPG5ILC-0?rel=0&autoplay=1&start=0&end=9) (0:09)
2. [OEM Setup Example: Milestone XProtect](https://www.youtube.com/embed/dxiPG5ILC-0?rel=0&autoplay=1&start=9&end=138) (2:18)
3. [Failover Scenarios Explained](https://www.youtube.com/embed/dxiPG5ILC-0?rel=0&autoplay=1&start=138&end=247) (1:49)
4. [Wrap-Up: Add OEM HA to Your Catalog](https://www.youtube.com/embed/dxiPG5ILC-0?rel=0&autoplay=1&start=247) (0:15)

[Free trial here](https://safekit.evidian.com/products/high-availability-software-for-application-clustering/windows-high-availability-software-synchronous-replication-failover/safekit-quick-installation-guide-for-a-new-windows-application-with-real-time-replication-and-failover/)

### [SafeKit Video: Network Load Balancing Clustering (5:03)](https://www.youtube.com/embed/XSMV_eM-jgk?rel=0&autoplay=1)

#### Chapters

1. [2 nodes with Apache](https://www.youtube.com/embed/XSMV_eM-jgk?rel=0&autoplay=1&start=0&end=13) (0:13)
2. [Configure the cluster and the farm.safe module](https://www.youtube.com/embed/XSMV_eM-jgk?rel=0&autoplay=1&start=13&end=153) (2:20)
3. [Start and test network load balancing, failover on crash](https://www.youtube.com/embed/XSMV_eM-jgk?rel=0&autoplay=1&start=153) (2:30)

[Free trial here](https://safekit.evidian.com/products/high-availability-software-for-application-clustering/windows-load-balancing-failover/safekit-quick-installation-guide-for-a-new-windows-application-with-network-load-balancing-and-failover/)

### [SafeKit Video: Free Certification Platform Tutorial (6:11)](https://www.youtube.com/embed/ijH4zXtn_3s?rel=0&autoplay=1)

#### Chapters

1. [The Training and Certification Platform](https://www.youtube.com/embed/ijH4zXtn_3s?rel=0&autoplay=1&start=0&end=102) (1:41)
2. [What is a SafeKit Training Module?](https://www.youtube.com/embed/ijH4zXtn_3s?rel=0&autoplay=1&start=101&end=218) (1:57)
3. [How to Earn a SafeKit Certificate?](https://www.youtube.com/embed/ijH4zXtn_3s?rel=0&autoplay=1&start=218&end=318) (1:40)
4. [Share Your Certificate on LinkedIn](https://www.youtube.com/embed/ijH4zXtn_3s?rel=0&autoplay=1&start=318) (0:53)

[Training and certification platform here](https://training.my.evidian.com/)

### [SafeKit Video: Competition and Cluster Architectures (13:21)](https://www.youtube.com/watch?v=DKra6YVLGZk)

#### Chapters

1. [Introduction](https://www.youtube.com/embed/DKra6YVLGZk?autoplay=1&start=0&end=250) (4:10)
2. [Cluster of virtual machines](https://www.youtube.com/embed/DKra6YVLGZk?autoplay=1&start=250&end=330) (1:20)
3. [Mirror cluster](https://www.youtube.com/embed/DKra6YVLGZk?autoplay=1&start=330&end=694) (6:04)
4. [Farm cluster](https://www.youtube.com/embed/DKra6YVLGZk?autoplay=1&start=694) (1:46)

[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")

### [SafeKit Video: Console on Smartphone (0:54)](https://www.youtube.com/embed/W_qaeZmEozA?rel=0&autoplay=1)

### [SafeKit Video: Email Notifications on Failover (1:04)](https://www.youtube.com/embed/arSUU45_AJs?rel=0&autoplay=1)

## 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](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 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 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 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](data:image/svg+xml,%3Csvg%20xmlns='http://www.w3.org/2000/svg'%20viewBox='0%200%20300%20169'%3E%3C/svg%3E)![Failover 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 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 cluster](https://safekit.evidian.com/wp-content/uploads/2023/02/safekit-resynchro-alone-300.png)

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](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 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?

![SafeKit Web Console: High Availability configuration dashboard 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 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?

![SafeKit Web Console: Real-time monitoring of a 2-node mirror cluster showing PRIM and SECOND states with active data replication.](data:image/svg+xml,%3Csvg%20xmlns='http://www.w3.org/2000/svg'%20viewBox='0%200%20478%20376'%3E%3C/svg%3E)![SafeKit Web Console: Real-time monitoring of a 2-node mirror cluster showing PRIM and SECOND states with active data replication.](https://safekit.evidian.com/wp-content/uploads/2026/01/safekit-mirror-cluster-monitor.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.

## How the SafeKit farm cluster works?

### Virtual IP address in a farm cluster

![How the Evidian SafeKit farm cluster implements network load balancing and failover](data:image/svg+xml,%3Csvg%20xmlns='http://www.w3.org/2000/svg'%20viewBox='0%200%20300%20169'%3E%3C/svg%3E)![How the Evidian SafeKit farm cluster implements network load balancing and failover](https://safekit.evidian.com/wp-content/uploads/2023/02/safekit-up-up-up-300.png)

On the previous figure, the application is running on the 3 servers (3 is an example, it can be 2 or more). Users are connected to a virtual IP address.

The [virtual IP address](https://safekit.evidian.com/products/high-availability-software-for-application-clustering/how-a-virtual-ip-address-works/#farm) is configured locally on each server in the farm cluster.  
The input traffic to the virtual IP address is received by all the servers and split among them by a network filter inside each server's kernel.

SafeKit detects hardware and software failures, reconfigures network filters in the event of a failure, and offers configurable application checkers and recovery scripts.

### Load balancing in a network filter

The network load balancing algorithm inside the network filter is based on the identity of the client packets (client IP address, client TCP port). Depending on the identity of the client packet input, only one filter in a server accepts the packet; the other filters in other servers reject it.

Once a packet is accepted by the filter on a server, only the CPU and memory of this server are used by the application that responds to the request of the client. The output messages are sent directly from the application server to the client.

If a server fails, the farm heartbeat protocol reconfigures the filters in the network load balancing cluster to re-balance the traffic on the remaining available servers.

### Stateful or stateless applications

With a stateful application, there is session affinity. The same client must be connected to the same server on multiple TCP sessions to retrieve its context on the server. In this case, the SafeKit load balancing rule is configured on the client IP address. Thus, the same client is always connected to the same server on multiple TCP sessions. And different clients are distributed across different servers in the farm.

With a stateless application, there is no session affinity. The same client can be connected to different servers in the farm on multiple TCP sessions. There is no context stored locally on a server from one session to another. In this case, the SafeKit load balancing rule is configured on the TCP client session identity. This configuration is the one which is the best for distributing sessions between servers, but it requires a TCP service without session affinity.

### How to configure a SafeKit farm cluster?

![SafeKit Web Console: Farm cluster configuration for network load balancing and virtual IP management.](data:image/svg+xml,%3Csvg%20xmlns='http://www.w3.org/2000/svg'%20viewBox='0%200%20966%20616'%3E%3C/svg%3E)![SafeKit Web Console: Farm cluster configuration for network load balancing and virtual IP management.](https://safekit.evidian.com/wp-content/uploads/2026/01/safekit-farm-cluster-config.png)

The **SafeKit farm cluster** is designed for high availability and scalability of services. The configuration focuses on distributing incoming traffic across both nodes simultaneously:

* **Load Balanced Services (Macros tab):** Define the specific application services (e.g., Apache, IIS, Nginx) to be kept active on all nodes.
* **Heartbeat network(s):** Communication path(s) used to detect if a node has left the farm, triggering an immediate redistribution of the load.
* **Virtual IP (Farm VIP):** Unlike a mirror cluster, the Farm VIP is shared between nodes using kernel filtering algorithm to distribute network traffic.
* **Load Balancing Rules:** Define the traffic distribution policy based on the source IP address or port.
* **Checkers:** Monitor the application's health and trigger automatic restart if a process failure is detected.

### How to monitor a SafeKit farm cluster?

![SafeKit Console: Monitoring a 2-node Farm cluster showing both nodes in UP state with active load balancing.](data:image/svg+xml,%3Csvg%20xmlns='http://www.w3.org/2000/svg'%20viewBox='0%200%20473%20373'%3E%3C/svg%3E)![SafeKit Console: Monitoring a 2-node Farm cluster showing both nodes in UP state with active load balancing.](https://safekit.evidian.com/wp-content/uploads/2026/01/safekit-farm-cluster-monitor.png)

Monitoring a farm cluster provides visibility into the **Active-Active** nature of the infrastructure, where all nodes contribute to the application's performance (showing 2 nodes in this example):

* **UP State (50% on 2 nodes):** In a healthy farm, both nodes are in the "UP" (50%) state, meaning they are both actively receiving and processing client requests via the shared Virtual IP.
* **Automatic Re-balancing:** If one node fails, the console visually shows the remaining node taking 100% of the traffic. There is no "failover" delay, as the surviving node is already active (aside from a detection time of a few seconds).
* **Node Insertion:** When a repaired node is restarted, it transitions from "STOP" to "UP" and automatically starts receiving its portion of the load without administrator intervention.
* **No Data Sync:** Note that in a farm cluster, there is no "Orange" resynchronization state, as nodes are expected to be stateless or share a backend database (which can be protected separately in a mirror cluster).

Beyond simple status icons, the interface provides one-click node management, allowing you to manually stop or start a node for planned maintenance while the shared Virtual IP automatically redistributes traffic without interrupting user activity.