Alternative to Always On SQL Server for express and standard editions

The solution for Microsoft SQL Server

Evidian SafeKit brings high availability to Microsoft SQL Server between two redundant nodes with synchronous real-time replication of data and automatic failover.

The solution is independent of the Microsoft SQL Server edition and works with express and standard editions.

A generic product

SafeKit is a generic product. You can replicate more than SQL server data and logs. If your application is SQL Server-based with specific folders containing your configuration or other files, you can replicate them in the same way. And you can restart your own services in addition to SQL server services.

>> SafeKit installation guide with Microsoft SQL Server express and standard editions

Without Microsoft failover cluster

SafeKit works without Microsoft failover cluster as with Always On SQL Server. It is an all-in-one offer that brings virtual IP address, synchronous real-time replication of folders, automatic failover and failback, and more... SafeKit eliminates the need for shared disks and database enterprise editions.

Without domain controller and active directory

SafeKit works without configuring domain controller and active directory as with Always On SQL Server. This easy-to-deploy, cost-effective solution does not require any specific skills.

Without 3 nodes for quorum

SafeKit works without the need for 3 nodes for quorum as with Always On SQL Server. In case of network isolation, SafeKit implements a split brain checker with a ping to a router playing the role of witness. Moreover, multiple heartbeats can be easily configured in the product.

A complete solution

SafeKit solves:

hardware failures (20% of problems), including the complete failure of a computer room,
software failures (40% of problems), including restart of critical processes,
and human errors (40% of problems) thanks to its ease of use and its web console.

Step 1. Real-time replication

Server 1 (PRIM) runs the Microsoft SQL Server application. Clients are connected to a virtual IP address. SafeKit replicates in real time modifications made inside files through the network.

The replication is synchronous with no data loss on failure contrary to asynchronous replication.

You just have to configure the names of directories to replicate in SafeKit. There are no pre-requisites on disk organization. Directories may be located in the system disk.

Step 2. Automatic failover

When Server 1 fails, Server 2 takes over. SafeKit switches the virtual IP address and restarts the Microsoft SQL Server application automatically on Server 2.

The application finds the files replicated by SafeKit uptodate on Server 2. The application 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 (30 seconds by default) plus the application start-up time.

Redundancy 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.

We deliver application modules to implement redundancy at the application level (like the Microsoft SQL Server module provided in the free trial below). They are preconfigured for well known applications and databases. You can customize them with your own services, data to replicate, application checkers. And you can combine application modules to build advanced multi-level architectures.

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 at the virtual machine level

In this type of solution, the full Virtual Machine (VM) is replicated (Application + OS). And the full VM is restarted in case of failure.

The advantage is that there is no restart scripts to write per application and no virtual IP address to define. If you do not know how the application works, this is the best solution.

This solution 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 installation guide with Microsoft SQL Server

Package installation on Windows

Download the free version of SafeKit on 2 Windows nodes.

Note: the free version includes all SafeKit features. At the end of the trial, you can activate permanent license keys without uninstalling the package.
To open the Windows firewall, on both nodes start a powershell as administrator, and type
```
c:/safekit/private/bin/firewallcfg add
```
To initialize the password for the default admin user of the web console, on both nodes start a powershell as administrator, and type
```
c:/safekit/private/bin/webservercfg.ps1 -passwd pwd
```
1. Use aphanumeric characters for the password (no special characters).
2. pwd must be the same on both nodes.
Exclude from antivirus scans C:\safekit\ (the default installation directory) and all replicated folders that you are going to define.

Antiviruses may face detection challenges with SafeKit due to its close integration with the OS, virtual IP mechanisms, real-time replication and restart of critical services.

Step by step configuration

4. 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.
Check that the replicated directories are installed on both nodes and contain the application data.
Replication of data and also logs is required for a database.
You can add new replicated directories as needed.
Enter a virtual IP address. A virtual IP address is a standard IP address in the same IP network (same subnet) as the IP addresses of both nodes.
Application clients must be configured with the virtual IP address (or the DNS name associated with the virtual IP address).
The virtual IP address is automatically switched in the event of a failure.
start_prim and stop_prim must contain starting and stopping of the Microsoft SQL Server application.
You can add new services in these scripts.
Check that the names of the services in these scripts are those installed on both nodes, otherwise modify them in the scripts.
Stop the services configured in start_prim on both nodes.
On Windows and on both nodes, with the Windows services manager, set Boot Startup Type = Manual for all the services registered in start_prim (SafeKit controls the start of services in start_prim).

Note that if a process name is displayed in Process Checker, it will be monitored with a restart action in case of failure. Configuring a wrong process name will cause the module to stop right after its start.

This operation will report the configuration in the userconfig.xml, start_prim, stop_prim files on both nodes (more information in the training with the command line).

7. 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 the status is ALONE (green) and the application is not started, check output messages of start_prim in the Application Log of node 1.

If node 1 does not reach ALONE (green) state, analyze why with the Module Log of node 1.

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

10. 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).
And with Microsoft Management Console (MMC) on Windows or with command lines on Linux, check the failover of Microsoft SQL Server services (stopped on node 1 in the stop_prim script and started on node 2 in the start_prim script).

If the Microsoft SQL Server application is not started on node 2 while the state is ALONE (green), check output messages of the start_prim script in the Application Log of node 2.

If ALONE (green) is not reached, analyze why with the Module Log of node 2.

More information on tests in the User's Guide.

Learn more

Internals

Internals of a SafeKit / Microsoft SQL Server high availability cluster with synchronous replication and failover

Go to the Advanced Configuration tab in the console, for editing these files

Internal files of the Windows sqlserver.safe module

userconfig.xml (description in the User's Guide)

<!DOCTYPE safe>
<safe>
<service mode="mirror" defaultprim="alone" maxloop="3" loop_interval="24" failover="on">
  <!-- Heartbeat Configuration -->
  <!-- Names or IP addresses on the default network are set during initialization in the console -->
  <heart pulse="700" timeout="30000">
    <heartbeat name="default" ident="flow">
    </heartbeat>
  </heart>
  <!-- Virtual IP Configuration -->
  <!-- Replace
     * VIRTUAL_TO_BE_DEFINED by the name of your virtual server 
  -->
  <vip>
    <interface_list>
        <interface check="on" arpreroute="on"> 
	  <real_interface>
               <virtual_addr addr="VIRTUAL_TO_BE_DEFINED" where="one_side_alias" />
          </real_interface>
        </interface>
    </interface_list>
  </vip>
  <!-- Software Error Detection Configuration -->
  <errd polltimer="10">
    <!-- Microsoft SQL Server process -->
    <proc name="sqlservr.exe" atleast="1" action="restart" class="prim" />
    <proc name="sqlagent.exe" atleast="1" action="restart" class="prim" />
    <proc name="sqlwriter.exe" atleast="1" action="restart" class="prim" />
  </errd>
  <!-- File Replication Configuration -->
  <!-- Replace
     * YOUR_INSTANCE to set the directory of your Microsoft SQL Server database and logs
  -->
  <rfs async="second" acl="off" nbrei="3">
	<replicated dir="C:\Program Files\Microsoft SQL Server\YOUR_INSTANCE\MSSQL\DATA" mode="read_only" />
	<replicated dir="C:\Program Files\Microsoft SQL Server\YOUR_INSTANCE\MSSQL\Log" mode="read_only" />
  </rfs>
  <!-- User scripts activation -->
  <user nicestoptimeout="300" forcestoptimeout="300" logging="userlog" />
</service>
</safe>

start_prim.cmd

@echo off
rem Script called on the primary server for starting application services 

rem For logging into SafeKit log use:
rem "%SAFE%\safekit" printi | printe "message"

rem stdout goes into Application log
echo "Running start_prim %*" 

set res=0

net start "MSSQLServer" > nul
if not %errorlevel% == 0 (
  %SAFE%\safekit printi "MSSQLServer start failed"
) else (
  %SAFE%\safekit printi "MSSQLServer started"
)

net start "SQLServerAgent" > nul
if not %errorlevel% == 0 (
  %SAFE%\safekit printi "SQLServerAgent start failed"
) else (
  %SAFE%\safekit printi "SQLServerAgent started"
)

net start "SQLWriter" > nul
if not %errorlevel% == 0 (
  %SAFE%\safekit printi "SQLWriter start failed"
) else (
  %SAFE%\safekit printi "SQLWriter started"
)

if %res% == 0 goto end

:stop
set res=%errorlevel%
"%SAFE%\safekit" printe "start_prim failed"

rem uncomment to stop SafeKit when critical
rem "%SAFE%\safekit" stop -i "start_prim"

:end

stop_prim.cmd

@echo off
rem Script called on the primary server for stopping application services 

rem ----------------------------------------------------------
rem
rem 2 stop modes:
rem
rem - graceful stop
rem   call standard application stop with net stop
rem
rem - force stop (%1=force)
rem   kill application's processes
rem
rem ----------------------------------------------------------

rem For logging into SafeKit log use:
rem "%SAFE%\safekit" printi | printe "message"

rem stdout goes into Application log
echo "Running stop_prim %*" 

set res=0

rem default: no action on forcestop
if "%1" == "force" goto check

rem %SAFE%\safekit printi "Stopping SQLWriter..."
rem net stop "SQLWriter" /Y > nul

rem %SAFE%\safekit printi "Stopping SQLServerAgent..."
rem net stop "SQLServerAgent" /Y > nul

%SAFE%\safekit printi "Stopping MSSQLServer..."
net stop "MSSQLServer" /Y > nul

rem wait a little for a real stop of services
%SAFEBIN%\sleep 10
goto end

:check

rem call :checksrv "SQLWRITER"
rem call :checksrv "SQLServerAgent"
call :checksrv "MSSQLServer"

goto end

:checksrv
 set SERVICE=%1
 net stop %SERVICE% /Y  
 if NOT ERRORLEVEL 1 goto end
 sc query state= inactive | findstr %SERVICE%
 if NOT ERRORLEVEL 1 goto end
 "%SAFE%\safekit" stop -i "stop_prim : service not stopped" 
 exit


:end

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.

Key differentiators of a mirror cluster with replication and failover

Evidian SafeKit mirror cluster with real-time file replication and failover
3 products in 1 More info >	The SafeKit high availability software saves on Windows and Linux the cost of : external shared or replicated storage, load balancing boxes, enterprise editions of OS and databases SafeKit includes all clustering features: synchronous real-time file replication, monitoring of server / network / software failures, automatic application restart, virtual IP address switched in case of failure to reroute clients
Very simple configuration More info >	The cluster configuration is very simple and made by means of application modules. New services and new replicated directories can be added to an existing application module to complete a high availability solution All the configuration of clusters is made using a simple centralized web administration console There is no domain controller or active directory to configure as with Microsoft cluster
Synchronous replication More info >	The real-time replication is synchronous with no data loss on failure This is not the case with asynchronous replication
Fully automated failback More info >	After a failure when a server reboots, the replication failback procedure is fully automatic and the failed server reintegrates the cluster without stopping the application on the only remaining server This is not the case with most replication solutions particularly with replication at the database level. Manual operations are required for resynchronizing a failed server. The application may even be stopped on the only remaining server during the resynchonization of the failed server
Replication of any type of data More info >	The replication is working for databases but also for any files which shall be replicated This not the case for replication at the database level
File replication vs disk replication More info >	The replication is based on file directories that can be located anywhere (even in the system disk) This is not the case with disk replication where special application configuration must be made to put the application data in a special disk
File replication vs shared disk More info >	The servers can be put in two remote sites This is not the case with shared disk solutions
Remote sites and virtual IP address More info >	All SafeKit clustering features are working for 2 servers in remote sites. Replication requires an extended LAN type network (latency = performance of synchronous replication, bandwidth = performance of resynchronization after failure). If both servers are connected to the same IP network through an extended LAN between two remote sites, the virtual IP address of SafeKit is working with rerouting at level 2 If both servers are connected to two different IP networks between two remote sites, the virtual IP address can be configured at the level of a load balancer with the "healh check" of SafeKit.
Quorum and split brain More info >	The solution works with only 2 servers and for the quorum (network isolation between both sites), a simple split brain checker to a router is offered to support a single execution of the critical application This is not the case for most clustering solutions where a 3^rd server is required for the quorum
Active/active cluster More info >	The secondary server is not dedicated to the restart of the primary server. The cluster can be active-active by running 2 different mirror modules This is not the case with a fault-tolerant system where the secondary is dedicated to the execution of the same application synchronized at the instruction level
Uniform high availability solution More info >	SafeKit implements a mirror cluster with replication and failover. But it imlements also a farm cluster with load balancing 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 This is not the case with an architecture mixing different technologies for load balancing, replication and failover
RTO / RPO More info >	SafeKit implements quick application restart in case of failure: around 1 mn or less Quick application restart is not ensured with full virtual machines replication. In case of hypervisor failure, a full VM must be rebooted on a new hypervisor with a recovery time depending on the OS reboot as with VMware HA or Hyper-V cluster

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 More info >	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 This is not the case with network load balancers This is not the case with dedicated proxies on Linux This is not the case with a specific multicast Ethernet address on Windows
All clustering features More info >	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 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 The cluster configuration is very simple and made by means of application modules. There is no domain controller or active directory to configure on Windows. The solution works on Windows and Linux
Remote sites and virtual IP address More info >	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 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 with the help of the SafeKit health check. Thus you can implement load balancing but also all the clustering features of SafeKit, in particular monitoring and automatic recovery of the critical application on application servers
Uniform high availability solution More info >	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 This is not the case with an architecture mixing different technologies for load balancing, replication and failover

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

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 Wisenet Wave > Hanwha Wisenet SSM >	-
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 >

Alternative to Always On SQL Server for express and standard editions

Evidian SafeKit without failover cluster, without domain controller and active directory, without 3 nodes for quorum