How the Evidian SafeKit software simply implements Windows load balancing and failover without network load balancers or dedicated proxy servers

How the Evidian SafeKit farm cluster implements Windows load balancing and failover?

Evidian SafeKit brings load balancing and failover to Windows. This article explains how to implement quickly a Windows cluster without network load balancers or dedicated proxy servers. SafeKit is installed directly on the Windows servers. The high availabity module farm.safe and a free trial are offered in the Installation tab below.

Note that you can implement with the same product real-time replication and failover of the back-end application like Microsoft SQL Server, PostgreSQL or other applications: see examples of mirror modules here.

This clustering solution is recognized as the simplest to implement by our customers and partners. It is also a complete solution that solves hardware failures (20% of problems) including the complete failure of a computer room, software failures (40% of problems) including smooth upgrade server by server and human errors (40% of problems) thanks to its simplicity of administration.

On the previous figure, Windows services are running of the 3 servers. Users are connected to a virtual IP address which is configured locally on each server. The input traffic for the virtual IP address is received by all the servers and split among them by a filter inside each server's kernel.

The network load balancing algorithm inside the 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 Windows services that responds to the request of the client. The output messages are sent directly from the Windows server to the client.

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

Installation of a SafeKit / Windows load balancing cluster with failover

Package installation on Windows

  • Install the free version of SafeKit on 2 Windows nodes (or more)

  • The module contains the files userconfig.xml, start_both and stop_both described later in the internals section
  • The module farm.safe is delivered inside the package.
  • To open the Windows firewall, on both nodes start a command line as administrator, goto C:\safekit\private\bin and type  .\firewallcfg.cmd add 

Continue with Configuration tab

SafeKit High Availability Differentiators against Competition

Evidian SafeKit farm cluster with load balancing and failover

No load balancer or dedicated proxy servers or special multicast Ethernet address No load balancer or dedicated proxy servers

Like   The solution does not require load balancers or dedicated proxy servers above the farm for imlementing load balancing. SafeKit is installed directly on the application servers in the farm. The load balancing is based on a standard virtual IP address/Ethernet MAC address and is working with physical servers or virtual machines on Windows and Linux without special network configuration

Dislike  This is not the case with network load balancers

Dislike  This is not the case with dedicated proxies on Linux

Dislike  This is not the case with a specific multicast Ethernet address on Windows

All clustering features All clustering features

Like  The solution includes all clustering features: virtual IP address, load balancing on client IP address or on sessions, server failure monitoring, network failure monitoring, software failure monitoring, automatic application restart with a quick revovery time and a replication option with a mirror module

Dislike  This is not the case with other load balancing solutions. They are able to make load balancing but they do not include a full clustering solution with restart scripts and automatic application restart in case of failure. They do not offer a replication option

Like   The cluster configuration is very simple and made by means of a high availability application module. There is no domain controller or active directory to configure on Windows. The solution works on Windows and Linux

Remote sites Remote sites

Like   If servers are connected to the same IP network through an extended LAN between remote sites, the virtual IP address of SafeKit is working with load balancing at level 2

Like   If servers are connected to different IP networks between remote sites, the virtual IP address can be configured at the level of a load balancer. SafeKit offers a health check: the load balancer is configured with a URL managed by SafeKit which returns OK on the UP servers and NOT FOUND else. This solution is implemented for SafeKit in the Cloud but it can be also implemented with a load balancer on premise. Thus you can implement load balancing but also all the clustering features of SafeKit including an easy administration of the cluster through the SafeKit web console

Uniform high availability solution Uniform high availability solution

Like  SafeKit imlements a farm cluster with load balancing and failover. But it implements also a mirror cluster with replication and failover. Thus a N-tiers architecture can me made highly available and load balanced with the same solution on Windows and Linux (same installation, configuration, administration with the SafeKit console or with the command line interface). This is unique on the market

Dislike  This is not the case with an architecture mixing different technologies for load balancing, replication and failover

High availability architectures comparison

(click on the feature for more information)

FeatureSafeKit clusterOther clusters
Software clustering vs hardware clustering A software cluster with SafeKit installed on two servers
A simple software cluster with the SafeKit package just installed on two servers
Hardware clustering with external shared storage Network load balancers or dedicated proxy servers

Complex hardware clustering with external storage or network load balancers
Shared nothing vs a shared disk cluster SafeKit shared-nothing cluster: easy to deploy even in remote sites
SafeKit is a shared-nothing cluster: easy to deploy even in remote sites
Shared disk cluster: complex to deploy
A shared disk cluster is complex to deploy
Application High Availability vs Full Virtual Machine High Availability
SafeKit application HA supports hardware failure, software failure, human errors with quick recovery time
Virtual machines high availability supports only hardware failure with an unknown recovery time
Full virtual machines HA supports only hardware failure with a VM reboot and an unknown recovery time if the OS reboot does not work
Synchronous replication vs asynchronous replication
SafeKit implements real-time synchronous replication with no data loss in case of failure
Asynchronous replication with data loss on failure
With asynchronous replication, there is data loss on failure
Byte-level file replication vs block-level disk replication SafeKit cluster with byte-level file replication: simply replicates directories even in the system disk
SafeKit implements real-time byte-level file replication and is simply configured with application directories to replicate even in the system disk
Cluster with block-level disk replication: complex and require to put application data in a special disk
Block-level disk replication is complex to configure and requires to put application data in a special disk
Heartbeat, failover and quorum to avoid 2 master nodes Simple quorum in a SafeKit cluster with a split brain checker configured on a router
To avoid 2 masters, SafeKit proposes a simple split brain checker configured on a router
Complex quorum in other clusters: third machine, special quorum disk, remote hardware reset
To avoid 2 masters, other clusters require a complex configuration with a third machine, a special quorum disk, a special interconnect
Network load balancing No special network configuration in a SafeKit cluster
No dedicated server and no special network configuration are required in a SafeKit cluster for network load balancing
Special network configuration in other clusters
Special network configuration is required in other clusters for network load balancing

Customers of SafeKit High Availability Software in all Business Activities

Demonstrations of SafeKit High Availability Software

SafeKit Webinar

This webinar presents in 10 minutes Evidian SafeKit.

In this webinar, you will understand:

  • mirror and farm clusters
  • cost savings against hardware clustering solutions
  • best use cases
  • the integration process for a new application

Microsoft SQL Server Cluster

This video shows a mirror module configuration with synchronous real-time replication and failover.

The file replication and the failover are configured for Microsoft SQL Server but it works in the same manner for other databases.

Free trial here

Apache Cluster

This video shows a farm module configuration with load balancing and failover.

The load balancing and the failover are configured for Apache but it works in the same manner for other web services.

Free trial here

Hyper-V Cluster

This video shows a Hyper-V cluster with full replications of virtual machines.

Virtual machines can run on both Hyper-V servers and they are restarted in case of failure.

Free trial here

Free On-Line Training on SafeKit High Availability Software