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 
  • For a clean boot and shutdown of SafeKit, on both nodes start a command line as administrator, goto C:\safekit\private\bin and type  .\addStartupShutdown.cmd

Continue with Configuration tab

SafeKit High Availability Differentiators against Competition

Key differentiators of a farm cluster with load balancing and failover

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, monitoring of server/network/software failures, 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 with the farm.safe 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 be 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

Feature

SafeKit cluster

Other clusters

Software clustering vs hardware clustering
More information...
A software cluster with SafeKit installed on two servers

Like  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



Dislike  Complex hardware clustering with external storage or network load balancers
Shared nothing vs a shared disk cluster
More information...
SafeKit shared-nothing cluster: easy to deploy even in remote sites

Like  SafeKit is a shared-nothing cluster: easy to deploy even in remote sites
Shared disk cluster: complex to deploy

Dislike  A shared disk cluster is complex to deploy
Application High Availability vs Full Virtual Machine High Availability
More information...


Like  Application HA supports hardware failure and software failure with a quick recovery time (RTO around 1 mn or less).
Smooth upgrade of application and OS possible server by server (version N and N+1 can coexist)
Virtual machines high availability supports only hardware failure with an recovery time depending on the OS reboot

Dislike  Full virtual machines HA supports only hardware failure with a VM reboot and a recovery time depending on the OS reboot.
Smooth upgrade not possible
High availability vs fault tolerance SafeKit high availability vs fault-tolerance

Like  No dedicated server. Each server can be the failover server of the other one.
Software failure with restart in another OS environment.
Smooth upgrade of application and OS possible server by server (version N and N+1 can coexist)
Fault tolerance system

Dislike  Secondary server dedicated to the execution of the same application synchronized at the instruction level.
Software exception on both servers at the same time.
Smooth upgrade not possible
Synchronous replication vs asynchronous replication
More information...


Like  SafeKit implements real-time synchronous replication with no data loss in case of failure
Asynchronous replication with data loss on failure

Dislike  With asynchronous replication, there is data loss on failure
Byte-level file replication vs block-level disk replication
More information...
SafeKit cluster with byte-level file replication: simply replicates directories even in the system disk

Like  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

Dislike  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
More information...
Simple quorum in a SafeKit cluster with a split brain checker configured on a router

Like  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

Dislike  To avoid 2 masters, other clusters require a complex configuration with a third machine, a special quorum disk, a special interconnect
Network load balancing
More information...
No special network configuration in a SafeKit cluster

Like  No dedicated proxy servers and no special network configuration are required in a SafeKit cluster for network load balancing
Special network configuration in other clusters

Dislike  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

SafeKit Modules for Plug&Play High Availability Solutions

SafeKit Modules for Plug&Play High Availability Solutions

Network load balancing and failover: click on the blue buttons

Farm modules

Windows

Linux

IIS-
Apache
New application
Amazon AWS farm
Microsoft Azure farm
Google GCP farm
Cloud generic farm

Real-time file replication and failover: click on the blue buttons

Mirror modules

Windows

Linux

Microsoft SQL Server-
Oracle
MySQL
PostgreSQL
Firebird
Hyper-V-
Milestone XProtect-
Hanwha Wisenet SSM-
New application
Amazon AWS mirror
Microsoft Azure mirror
Google GCP mirror
Cloud generic mirror