Siemens SIMATIC PCS 7 cluster without shared storage on a SAN

The solution for Siemens SIMATIC PCS7

Evidian SafeKit brings high availability to Siemens SIMATIC PCS7 between two servers of any brand.

This article explains how to implement quickly a Siemens SIMATIC PCS7 cluster without shared storage on a SAN and without specific skills.

The principle of the solution is to put Siemens SIMATIC PCS7 in a virtual machine under Hyper-V. SafeKit implements real-time replication and automatic failover of the virtual machine.

Note that Hyper-V is the free hypervisor included in all Windows versions (even Windows for PC).

Save costs with this solution

There is no need for complex VMware-type solution with three servers and shared storage on a SAN. With SafeKit, you will have instead synchronous real-time replication and failover of several virtual machines between two servers.

And with the standard Hyper-V manager GUI, you will be able to manage very simply your virtual machines.

Note that you can implement with the SafeKit product real-time replication and failover of any file directory and service, database, complete Hyper-V or KVM virtual machines, Docker, Podman, K3S, Cloud applications (see the module list).

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...).

Solution for a new application (restart scripts to write): Windows, Linux

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 quick installation guide with the Hyper-V module

Step by step configuration

1. Prerequisites

The VM1 virtual machine files (VM1 configuration file, virtual hard disk...) must be put in a same folder: this folder will be replicated by SafeKit.

Make sure the virtual switch name(s) referenced by the virtual machine exist on both Hyper-V servers and corresponds to the same physical network.

It is important that all the files representing a VM (Virtual Machines/, Virtual Hard Disks/, .vmcx, .vmgs, .vmrs, .vhdx, ...) are in the same directory replicated by SafeKit. Else your VM will not reboot after replication. If you are not sure, take a snapshot or your VM before starting the procedure.

If all the files of VM1 are not in the same folder, use Hyper-V manager:

Export VM1 in a folder, for example in D:\Repli-Hyper-V
This export will create a folder D:\Repli-Hyper-V\VM1\ containing all VM1 files
Remove VM1 from the inventory of Hyper-V manager
Import VM1, previously exported, into Hyper-V manager

3. Configure node addresses

Enter the node IP addresses, press the Tab key to check connectivity and fill node names.
Then, click on Save and apply to save the configuration.

If either node1 or node2 has a red color, check connectivity of the browser to both nodes and check firewall on both nodes for troubleshooting.

If you want, you can add a new LAN for a second heartbeat and for a dedicated replication network.

This operation will place the IP addresses in the cluster.xml file on both nodes (more information in the training with the command line).

5. Configure the module

Choose an Automatic start of the module at boot without delay.
Normally, you have a single Heartbeat network on which the replication is made. But, you can define a private network if necessary (by adding a LAN at step 3).
Put in VM_PATH, the root path of the replicated directory (D:\Repli-Hyper-V).
Enter in VM_NAME, the name of the virtual machine (VM1).

We assume that all VM1 files are in D:\Repli-Hyper-V\VM1\ (see prerequisites). This directory will be replicated in real-time by SafeKit.

The NORMAL_STOP and FORCE_STOP values can be "stop", "save" or "off":

"stop" shutdowns the VM when the module is stopped.
"save" saves the current state of the VM (suspend) when the module is stopped.
"off" turns off the VM (power off) when the module is stopped.

"stop" is recommended because it causes the shutdown then the reboot of the VM when the module is stopped and restarted. Thus, if the application inside the VM fails, it is restarted.

This will be the case, for example, when switching between primary and secondary roles.

You do not need to configure a virtual IP address. VM1 will be rebooted on the secondary Hyper-V with its physical IP address, and this IP address will be rerouted.

10. Start the node with up-to-date data

If node 1 has the up-to-date replicated directory for VM1/, select it and start it As primary.

When node 2 will be started, all data will be copied from node 1 to node 2.

If you make the wrong choice, you run the risk of synchronizing outdated data on both nodes.

It is also assumed that VM1 is stopped on node 1 so that SafeKit installs the replication mechanisms and then starts VM1 in the start_prim script.

Use Start for subsequent starts: SafeKit retains the most up-to-date server. Starting As primary is a special start-up the first time or during exceptional operations.

11. Wait for the transition to ALONE (green)

Node 1 should reach the ALONE (green) state, which means that the start_prim script has been executed on node 1.

If ALONE (green) is not reached or if VM1 is not started, analyze why with the module log of node 1.

click on node1 to open the module log and check if there are error messages.
click on start_prim message in the log: output messages of the script will be displayed and errors can be detected.

If the cluster is in WAIT (red) not uptodate, STOP (red) not uptodate state, stop the WAIT node and force its start as primary.

14. Testing

Stop the PRIM node by scrolling down its contextual menu and clicking Stop.
Verify that there is a failover on the SECOND node which should become ALONE (green).
Check with Hyper-V manager that VM1 is running on node 2.

If ALONE (green) is not reached or if VM1 is not started on node2, analyze why with the module log of node 2.

click on node2 to open the module log and check if there are error messages.
click on start_prim message in the log: output messages of the script will be displayed and errors can be detected.

As the start_prim script imports the virtual machine on node 2, the failover can fail because of Hyper-V settings (see this article).

If everything is okay, initiate a start on node1, which will resynchronize the replicated directories from node2.

If things go wrong, stop node2 and force the start as primary of node1, which will restart with its locally healthy data at the time of the stop.

More information on tests in the User's Guide.

The custom checker sends heartbeat messages from the host to the VM at regular intervals. It is then the job of the Hyper-V Heartbeat Service installed on the VM to send a response to each of these heartbeat messages. If the Hyper-V Heartbeat Service does not respond to the message, then the custom checker restarts the VM on the same Hyper-V. If after 3 unsuccessful restarts (maxloop) in 24 hours (loop_interval), then the SafeKit hyperv module stops on the primary server and there is a failover of the VM on the secondary server. There is also a configuration with a direct failover on the other Hyper-V server as soon as the VM does not respond to heartbeats.

How to change userconfig.xml to configure the custom checker

In the module configuration, click on Advanced Configuration (see image) to edit userconfig.xml.

Declare the custom checker by adding in the <check> section of userconfig.xml:

<service mode="mirror" maxloop="3" loop_interval="24" ...>
 ...
 <check>
  ...
  <custom ident="VM1" exec="vmcheck.ps1" arg="%VM_NAME%" when="prim" action="restart" ></custom>
 </check>
 ...

Save and apply the new configuration to redeploy the modified userconfig.xml file on both nodes (module must be stopped on both nodes to save and apply).

Parameters:

ident="VM1" identifies the virtual machine with a resource name: custom.VM1. Change this value to identify your virtual machine.
exec="vmcheck.ps1" references the script delivered with the module. Do not change this value.
arg="%VM_NAME%" is an argument for the script. Do not change this value.
when="prim" means that the checker runs only on the primary. Do not change this value.
action="restart" means a local restart of the VM. If the restart fails locally 3 times in 24 Hours (maxloop/loop_interval), then the VM is restarted on the other node.
action="stopstart" means an immediate failover on the secondary node.

16. Automatic restart if a critical service fails inside the VM

If you want an automatic restart or failover when a critical service inside the VM fails, you can configure the Recovery properties of the service (see image).

First you must configure the custom checker previously described.

And then in Microsoft Service Manager inside the VM, select your critical service and in the recovery property of the service, you just have to configure shutdown of the VM when the critical service fails.

For that, in the Recovery options of your critical service, choose "Run a Program" on failures and in Run program options, set"C:\Windows\System32\shutdown.exe" and in "Command line parameters", set /s /c "service fails".

Of course, you can implement more subtle recovery with your own scripts. But just be aware that shutting down the VM will enable the custom checker in the host. The custom checker will detect that the Hyper-V heartbeat is no more responding and will restart the VM on the same Hyper-V server or will make a failover on the other Hyper-V server (depending on its configuration).

To test the feature, use Task Manager and kill the process (End task) associated to the critical service. A clean stop of the service through Service Manager or the "net stop" command does not trigger the recovery action inside Windows Service Manager.

19. If necessary, configure a splitbrain checker

See below "What are the different scenarios in case of network isolation in a cluster?" to know if you need to configure a splitbrain checker.
In the module configuration, click on Advanced Configuration (see image) to edit userconfig.xml.

Declare the splitbrain checker by adding in the <check> section of userconfig.xml:

<service>
 ...
 <check>
  ...
  <splitbrain ident="witness" exec="ping" arg="witness IP"/>
 </check>

Save and apply the new configuration to redeploy the modified userconfig.xml file on both nodes (module must be stopped on both nodes to save and apply).

Parameters:

ident="witness" identifies the witness with a resource name: splitbrain.witness. You can change this value to identify the witness.
exec="ping" references the ping code to execute. Do not change this value.
arg="witness IP" is an argument for the ping. Change this value with the IP of the witness (a robust element, typically a router).

When there is a network isolation, the behavior with a split-brain checker is:

a split-brain checker has been configured with the IP address of a witness (typically a router),
the split-brain checker operates when a server goes from PRIM to ALONE or from SECOND to ALONE,
in case of network isolation, before going to ALONE, both nodes test the IP address,
the node which can access the IP address goes to ALONE, the other one goes to WAIT,
when the isolation is repaired, the WAIT node resynchronizes its data and becomes SECOND.

Note: If the witness is down or disconnected, both nodes go to WAIT and the application is no more running. That's why you must choose a robust witness like a router.

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.

Key differentiators of SafeKit vs Microsoft Hyper-V cluster and VMware HA

Key differentiators of high availability at the virtual machine level or at the application level

Key differentiators of the SafeKit high availability technology

Software clustering vs hardware clustering More info >
A simple software cluster with the SafeKit package just installed on two servers	Complex hardware clustering with external storage or network load balancers
Shared nothing vs a shared disk cluster More info >
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 More info >
Application HA supports hardware failure and software failure with a quick recovery time (RTO around 1 mn or less). Application HA requires to define restart scripts per application and folders to replicate (SafeKit application modules).	Full virtual machines HA supports only hardware failure with a VM reboot and a recovery time depending on the OS reboot. No restart scripts to define with full virtual machines HA (SafeKit hyperv.safe or kvm.safe modules). Hypervisors are active/active with just multiple virtual machines.
High availability vs fault tolerance More info >
No dedicated server with SafeKit. 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)	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 info >
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 More info >
SafeKit implements real-time byte-level file replication and is simply configured with application 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 More info >
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
Virtual IP address primary/secondary, network load balancing, failover More info >
No dedicated proxy servers and no special network configuration are required in a SafeKit cluster for virtual IP addresses	Special network configuration is required in other clusters for virtual IP addresses. Note that SafeKit offers a health check adapted to load balancers

Advanced clustering architectures

Several modules can be deployed on the same cluster. Thus, advanced clustering architectures can be implemented:

the farm+mirror cluster built by deploying a farm module and a mirror module on the same cluster,
the active/active cluster with replication built by deploying several mirror modules on 2 servers,
the Hyper-V cluster or KVM cluster with real-time replication and failover of full virtual machines between 2 active hypervisors,
the N-1 cluster built by deploying N mirror modules on N+1 servers.

Advanced configuration

Mirror module / pptx
- start_prim / stop_prim scripts
- userconfig.xml
- Heartbeat (<hearbeat>)
- Virtual IP address (<vip>)
- Real-time file replication (<rfs>)
- How real-time file replication works?
- Mirror's states in action
Farm module / pptx
- start_both / stop_both scripts
- userconfig.xml
- Farm heartbeats (<farm>)
- Virtual IP address (<vip>)
- Farm's states in action

Checkers / pptx
- userconfig.xml
- errd checker
- intf and ip checkers
- custom checker
- splitbrain checker for a mirror module
- tcp, ping, module checkers
- Checkers in action

SafeKit with the Hyper-V module or the KVM module	Microsoft Hyper-V Cluster & VMware HA

No shared disk - synchronous real-time replication instead with no data loss	Shared disk and specific extenal bay of disk
Remote sites = no SAN for replication	Remote sites = replicated bays of disk across a SAN
No specific IT skill to configure the system	Specific IT skills to configure the system

VM HA with the SafeKit Hyper-V or KVM module	Application HA with SafeKit application modules
SafeKit inside 2 hypervisors SafeKit replication and failover of full VM	SafeKit inside 2 virtual or physical machines SafeKit replication and failover at application level
Replicates more data (App+OS)	Replicates only application data
Reboot of VM on hypervisor 2 if hypervisor 1 crashes Recovery time depending on the OS reboot	Quick recovery time with restart of App on OS2 if crash of server 1 Around 1 mn or less (see RTO/RPO here) Application checker and software failover
Generic solution for any application / OS	Restart scripts to be written in application modules

Network load balancing and failover
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 >

Real-time file replication and failover
Windows mirror	Linux mirror
Generic Windows mirror >	Generic Linux mirror >
Microsoft SQL Server >	-
Oracle >
MariaDB >
MySQL >
PostgreSQL >
Firebird >
Windows Hyper-V >	Linux KVM >
-	Docker > Podman > Kubernetes K3S >
-	Elasticsearch >
Milestone XProtect >	-
Genetec SQL Server >	-
Hanwha Vision > Hanwha Wisenet >	-
Nedap AEOS >	-
Siemens SIMATIC WinCC > Siemens SIMATIC PCS 7 > Siemens Siveillance suite > Siemens Siveillance VMS > Siemens Desigo CC > Siemens SiPass > Siemens SIPORT >	-
Bosch AMS > Bosch BIS > Bosch BVMS >	-
Amazon AWS mirror >
Microsoft Azure mirror >
Google GCP mirror >
Other cloud >

Siemens SIMATIC PCS 7 cluster without shared storage on a SAN

[SafeKit] Synchronous real-time replication, high availability and migration of virtual machines between two servers

How the Evidian SafeKit software simply implements a Siemens SIMATIC PCS7 high availability cluster without shared storage on a SAN?

The solution for Siemens SIMATIC PCS7

A solution open to several applications

Save costs with this solution

About products under Siemens LMS licensing

SafeKit brings two solutions for redundancy and high availability of a SCADA software

Redundancy and high availability at the application level

Redundancy and high availability at the virtual machine level

SafeKit, a recognized solution on the SCADA market

Solution preferred by Siemens

SafeKit chosen by Alstef Group

Fives Syleps has chosen SafeKit

Comparison

Built-in Hyper-V replication

Microsoft clustering (same as VMware HA)

Evidian SafeKit

SafeKit free trial + Hyper-V mirror module for Siemens SIMATIC PCS 7 + quick installation guide

Prerequisites

Package installation on Windows

Module installation on Windows

1. Prerequisites

2. Launch the SafeKit console

3. Configure node addresses

4. Select a module

5. Configure the module

6. Edit scripts (optional)

7. Communication encryption (optional)

8. Save and apply

9. Verify successful configuration

10. Start the node with up-to-date data

11. Wait for the transition to ALONE (green)

12. Start node 2

13. Verify that the cluster is operational

14. Testing

15. Custom checker to detect VM malfunction

How to change userconfig.xml to configure the custom checker

16. Automatic restart if a critical service fails inside the VM

17. Remove the start of VM1 in Hyper-V at boot

18. Support

19. If necessary, configure a splitbrain checker

What are the different scenarios in case of network isolation in a cluster?

A single network

Two networks with a dedicated replication network

A single network and a splitbrain checker

How the SafeKit Hyper-V cluster works with replication and failover of Siemens SIMATIC PCS 7?

Step 1. Real-time replication

Step 2. Automatic failover

Step 3. Automatic failback

Step 4. Back to normal

Typical usage with SafeKit

Why a replication of a few Tera-bytes?

Why a replication < 1,000,000 files?

Why a failover ≤ 32 replicated VMs?

Why a LAN/VLAN network between remote sites?

SafeKit Customers in all Business Activities

Best use cases [+]

Video management, access control, building management [+]

TV broadcasting [+]

Finance [+]

Industry [+]

Air traffic control [+]

Bank [+]

Transport [+]

Healthcare [+]

Government [+]

Partners, the success with SafeKit

Building Management Software (BMS)

Video Management Software (VMS)

Electronic Access Control Software (EACS)

SCADA Software (Industry)

Evidian SafeKit Webinar

Redundancy and High Availability Differentiators against Competition

SafeKit Modules for Plug&Play Redundancy and High Availability Solutions

Network load balancing and failover

Advanced clustering architectures

Real-time file replication and failover

Evidian SafeKit 8.2

All new features compared to 7.5 described in the release notes