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Evidian > Products > High Availability Software - Zero Extra Hardware > Alternative to Always On SQL Server for express and standard editions

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

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.

Other redundancy and high availability solutions

With SafeKit, you can implement on Windows and Linux, real-time replication and failover of any folders and services, databases, complete Hyper-V or KVM virtual machines, Docker, Kubernetes, Cloud applications.

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.

How the SafeKit mirror cluster works with Microsoft SQL Server?

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. 

File replication at byte level in a mirror Microsoft SQL Server cluster

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.

Failover of Microsoft SQL Server in a mirror cluster

The failover time is equal to the fault-detection time (30 seconds by default) plus the application start-up time.

Step 3. Automatic failback

Failback involves restarting Server 1 after fixing the problem that caused it to fail.

SafeKit automatically resynchronizes the files, updating only the files modified on Server 2 while Server 1 was halted.

Failback in a mirror Microsoft SQL Server cluster

Failback takes place without disturbing the Microsoft SQL Server application, which can continue running on Server 2.

Step 4. Back to normal

After reintegration, the files are once again in mirror mode, as in step 1. The system is back in high-availability mode, with the Microsoft SQL Server application running on Server 2 and SafeKit replicating file updates to Server 1.

Return to normal operation in a mirror Microsoft SQL Server cluster

If the administrator wishes the application to run on Server 1, he/she can execute a "swap" command either manually at an appropriate time, or automatically through configuration.

Choose between redundancy at the application level or at the virtual machine level

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.

Application HA - redundancy at the application level

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.

VM HA - redundancy at the virtual machine level

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.

More comparison between VM HA vs Application HA

Typical usage with SafeKit

Why a replication of a few Tera-bytes?

Resynchronization time after a failure (step 3)

  • 1 Gb/s network ≈ 3 Hours for 1 Tera-bytes.
  • 10 Gb/s network ≈ 1 Hour for 1 Tera-bytes or less depending on disk write performances.

Alternative

Why a replication < 1,000,000 files?

  • Resynchronization time performance after a failure (step 3).
  • Time to check each file between both nodes.

Alternative

  • Put the many files to replicate in a virtual hard disk / virtual machine.
  • Only the files representing the virtual hard disk / virtual machine will be replicated and resynchronized in this case.

Why a failover ≤ 32 replicated VMs?

  • Each VM runs in an independent mirror module.
  • Maximum of 32 mirror modules running on the same cluster.

Alternative

  • Use an external shared storage and another VM clustering solution.
  • More expensive, more complex.

Why a LAN/VLAN network between remote sites?

Alternative

  • Use a load balancer for the virtual IP address if the 2 nodes are in 2 subnets (supported by SafeKit, especially in the cloud).
  • Use backup solutions with asynchronous replication for high latency network.

SafeKit Quick Installation Guides

New application (real-time replication and failover)


New application (network load balancing and failover)


Database (real-time replication and failover)


Web (network load balancing and failover)


Full VM or container real-time replication and failover


Amazon AWS


Google GCP


Microsoft Azure


Other clouds


Physical security (real-time replication and failover)


Siemens (real-time replication and failover)


SafeKit High Availability Differentiators