The SafeKit farm cluster implements a network load balancing cluster among several servers. It provides a simple solution to critical application scalability and high availability.
In a network load balancing cluster, the same application runs on each server, and the load is balanced by the distribution of network activity on the different servers of the farm. This type of cluster is suited to front-end applications like web services.
The SafeKit software saves the cost of hardware load balancers. It does not require specific servers above the farm for implementing the network load balancing cluster.
The network load balancing is very efficiently implemented by a network filter driver. This driver works on Windows and Linux (even on Windows editions for PCs).
SafeKit provides a generic farm module on Windows and Linux to build a network load balancing cluster. You can write your own farm module for your application starting from the generic farm module. Apache and Microsoft IIS are examples of farm modules.
Combined with the farm cluster, you can also implement a mirror cluster with real-time file replication and failover.
The virtual IP address is configured locally on each server in the network load balancing cluster.
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 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 SafeKit membership protocol reconfigures the filters in the network load balancing cluster to re-balance the traffic on the remaining available servers.
Note that a comparison between Microsoft NLB and SafeKit network load balancing is available here. And note that SafeKit network load balancing is working not only on Windows (including Windows editions for PCs) but also on Linux.
With a stateful server, there is session affinity. The same client must be connected to the same server on multiple HTTP/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. This configuration is used when there are session affinities.
With a stateless server, there is no session affinity. The same client can be connected to different servers in the farm on multiple HTTP/TCP sessions; because 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.
If you are also interested by real-time replication and failover in a mirror cluster, read this article.
Click on the Windows or Linux module to understand and try the solution
Mirror modules (replication and failover)
|Microsoft SQL Server||-|
|Milestone XProtect (based on Microsoft SQL Server)||-|
|Hanwha SSM (based on PostgreSQL)||-|
|Generic mirror module|
Farm modules (load balancing and failover)
|Generic farm module|
Click on the mirror/farm architecture to understand and try the solution
Real-time replication and failover cluster
Load balancing and failover cluster
In video surveillance systems, Evidian SafeKit implements high availability with synchronous replication and failover of
Harmonic is using SafeKit as a software OEM high availability solution and deploys it with its TV broadcasting solutions over satellites, terrestrials, cable, IPTV. Over 80 SafeKit clusters are deployed on Windows for replication of Harmonic database and automatic failover of the critical application. Philippe Vidal, Product Manager, Harmonic says: “SafeKit is the ideal application clustering solution for a software publisher looking for a simple and economical high availability software. We are deploying SafeKit worldwide and we currently have more than 80 SafeKit clusters on Windows with our critical TV broadcasting application through terrestrial, satellite, cable and IP-TV. SafeKit implements the continuous and real-time replication of our database as well as the automatic failover of our application for software and hardware failures. Without modifying our application, it was possible for us to customize the installation of SafeKit. Since then, the time of preparation and implementation has been significantly reduced.”
The European Society of Warranties and Guarantees in Natixis uses SafeKit as a high availability solution for its applications.
Over 30 SafeKit clusters are deployed on Unix and Windows in Natixis.
Fives Syleps, the Sydel software editor implements high availability of its ERP with SafeKit and deploys the solution in the food industry.
Tony Myers, Director of Business Development says:
“By developing applications for air traffic control, Copperchase is in one of the most critical business activities. We absolutely need our applications to be available all the time. We have found with SafeKit a simple and complete clustering solution for our needs. This software combines in a single product load balancing, real time data replication with no data loss and automatic failover. This is why, Copperchase deploys SafeKit for air traffic control in airports in the UK and the 30 countries where we are present.”
Software vendor Wellington IT deploys SafeKit high availability with its banking application for Credit Unions in Ireland and UK.
Peter Knight, Sales Manager says:
“Business continuity and disaster recovery are a major concern for our Locus banking application deployed in numerous Credit Unions around Ireland and the UK. We have found with SafeKit a simple and robust solution for high availability and synchronous replication between two servers with no data loss. With this software solution, we are not dependent on a specific and costly hardware clustering solution. It is a perfect tool to provide a software high availability option to an application of a software vendor.”
Paris transport company (RATP) chose the SafeKit high availability and load balancing solution for the centralized control room of line 1 of the Paris subway.
Stéphane Guilmin, RATP, Project manager says:
“Automation of line 1 of the Paris subway is a major project for RATP, requiring a centralized command room (CCR) designed to resist IT failures. With SafeKit, we have three distinct advantages to meet this need. Firstly, SafeKit is a purely software solution that does not demand the use of shared disks on a SAN and network boxes for load balancing. It is very simple to separate our servers into separate machine rooms. Moreover, this clustering solution is homogeneous for our Windows and Unix platforms. SafeKit provides the three functions that we needed: load balancing between servers, automatic failover after an incident and real time data replication.”
And also, Philippe Marsol, Atos BU Transport, Integration Manager says:
“SafeKit is a simple and powerful product for application high availability. We have integrated SafeKit in our critical projects like the supervision of Paris metro Line 4 (the control room) or Marseille Line 1 and Line 2 (the operations center). Thanks to the simplicity of the product, we gained time for the integration and validation of the solution and we had also quick answers to our questions with a responsive Evidian team.”
The software integrator Systel deploys SafeKit high-availability solution in firefighter and emergency medical call centers.
Marc Pellas, CEO says:
“SafeKit perfectly meets the needs of a software vendor. Its main advantage is that it brings in high availability through a software option that is added to our own multi-platform software suite. This way, we are not dependent on a specific and costly hardware clustering solution that is not only difficult to install and maintain, but also differs according to client environments. With SafeKit, our firefighter call centers are run with an integrated software clustering solution, which is the same for all our customers, is user friendly and for which we master the installation up to after-sales support.”
ERP high availability and load balancing of the French army (DGA) are made with SafeKit.
Alexandre Barth, Systems administrator says:
“Our production team implemented the SafeKit solution without any difficulty on 14 Windows and Linux clusters. Our critical activity is thus secure, with high-availability and load balancing functions. The advantages of this product are easy deployment and administration of clusters, on the one hand, and uniformity of the solution in the face of heterogeneous operating systems, on the other hand.”
|OEM Software||Distributed Enterprise||Remote Sites|
|A software publisher uses SafeKit as an OEM software for high availability of its application||A distributed enterprise deploys SafeKit in many branches without specific IT skills||SafeKit is deployed in two remote sites without the need for replicated bays of disks through a SAN|
1 - The ideal product for a software publisher
“SafeKit is the ideal application clustering solution for a software publisher. We currently have deployed more than 80 SafeKit clusters worldwide with our critical TV broadcasting application.”
2 - The product very easy to deploy for a reseller
“WithNCompany has deployed in South Korea many SafeKit high availability solutions with the Samsung Video Surveillance Platform. SafeKit is appreciated because the product is easy to install and very quickly deployed.”
3 - The product to gain time for a system integrator
“Thanks to a simple and powerful product, we gained time in the integration and validation of our critical projects like the supervision of Paris and Marseille metro lines (the control rooms).”
High availability architectures comparison
(click on the feature for more information)
|Feature||SafeKit cluster||Other clusters|
|Software clustering vs hardware clustering|| |
A simple software cluster with the SafeKit package installed on two servers
Complex hardware clustering with external storage or network load balancers
|Shared nothing vs a shared disk cluster|| |
SafeKit is a shared-nothing cluster: easy to deploy even in remote sites
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
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
With asynchronous replication, there is data loss on failure
|Byte-level file replication vs block-level disk replication|| |
SafeKit implements byte-level file replication and is simply configured with directories to replicate even in the system 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|| |
To avoid 2 masters, SafeKit proposes a simple split brain checker configured on a router
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 is required in a SafeKit cluster for network load balancing
Special network configuration is required in other clusters for network load balancing
RTO is the time during which the application is unavailable in case of failure. RTO of the SafeKit farm solution is in the order of a few seconds on hardware failure.
For a hardware failure, RTO = failure detection timeout through monitoring channels (default a few seconds): after the timeout the load balancing filters are reconfigured.
For a software failure or an administrator restart, RTO = time to (cleanly) stop services + time to restart them.