Redundancy and high availability at the application level
In this type of solution, only application data are replicated. And only the application is restared in case of failure.
With this solution, restart scripts must be written to restart the application. This solution is platform agnostic and works with applications inside physical machines, virtual machines, in the Cloud. Any hypervisor is supported (VMware, Hyper-V...).
Redundancy and high availability at the virtual machine level
In this type of solution, the SCADA software is put inside a virtual machine. The full Virtual Machine (VM) is replicated and restarted (Application + OS).
The advantage of this solution is that there is no restart scripts to write per application. This solution is generic for any SCADA software. It works with Windows/Hyper-V and Linux/KVM but not with VMware. This is an active/active solution with several virtual machines replicated and restarted between two nodes.
- Solution for a new application (no restart script to write): Windows/Hyper-V, Linux/KVM
SafeKit is available in the Siemens marketplace with its SCADA sofware: Desigo CC (building management), SIMATIC WinCC, SIMATIC PCS 7 and also with the Siveillance suite (video and access control).
SafeKit is deployed by Siemens in Australia, France, the Netherlands, Qatar, Switzerland, the UAE, the UK, the US.
Alstef Group, a key player in baggage handling systems, deploys SafeKit for redundancy and high availability of its SCADA software suite, BAGware.
SafeKit has been deployed by Alstef Group in many airports with BAGware.
Fives Syleps, a key player in automated logistics, deploys SafeKit for redundancy and high availability of its software suite.
SafeKit has been deployed by Fives Syleps in many factories.
- Asynchronous replication => data loss
- Manual failover (no automatic failover)
- Not a high availability solution
- Requires a shared disk
- Price of the shared disk and its installation (SAN, iSCSI)
- Configuration complexity of Windows failover cluster (AD…)
- Remote sites = replicated storage
- Simple and economical
- Synchronous replication => no data loss
- Automatic failover and failback
- No shared disk
- Free trial and quick installation guide
Step 1. Real-time replication
Server 1 (PRIM) runs the VM (virtual machine) containing Siemens SIMATIC PCS 7. SafeKit replicates in real time the VM files (virtual hard disk, VM configuration). Only changes made in the files are replicated across the network.
The replication is synchronous with no data loss on failure contrary to asynchronous replication.
You just have to configure the VM directory name in SafeKit. There are no pre-requisites on disk organization. The directory may be located in the system disk.
Step 2. Automatic failover
When Server 1 fails, Server 2 takes over. SafeKit restarts the VM containing Siemens SIMATIC PCS 7 on Server 2. Hyper-V finds the files replicated by SafeKit uptodate on Server 2.
The VM continues to run on Server 2 by locally modifying its files that are no longer replicated to Server 1.
The failover time is equal to the fault-detection time (set to 30 seconds by default) plus the VM reboot time.
Step 4. Back to normal
After reintegration, the VM files are once again in mirror mode, as in step 1. The system is back in high-availability mode, with the VM containing Siemens SIMATIC PCS 7 running on Server 2 and SafeKit replicating file updates to Server 1.
If the administrator wishes the VM to run on Server 1, he/she can execute a "swap" command either manually at an appropriate time, or automatically through configuration.
No shared disk - 
Shared disk and specific extenal bay of disk
Network load balancing and failover |
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| Windows farm | Linux farm |
| Generic Windows farm > | Generic Linux farm > |
| Microsoft IIS > | - |
| NGINX > | |
| Apache > | |
| Amazon AWS farm > | |
| Microsoft Azure farm > | |
| Google GCP farm > | |
| Other cloud > | |