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Hyper-V 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 Hyper-V high availability cluster without shared storage on a SAN?

The solution for Hyper-V

Evidian SafeKit brings high availability to Hyper-V between two servers of any brand.

This article explains how to implement quickly a Hyper-V cluster without shared storage on a SAN and without specific skills.

The principle of the solution is to put a critical application 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).

A solution open to several applications

Several applications can be put in several virtual machines replicated and restarted by SafeKit. You have the possibility to migrate each virtual machine between both servers with the SafeKit console and thus balance the load in an active-active cluster.

[SafeKit] A Hyper-V cluster without shared storage on a SAN

Save costs with this solution

There is no need for complex VMware-type solution with three servers and shared storage on a SAN or vSAN. 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 all solutions).

How the SafeKit Hyper-V cluster works with replication and failover of if(htmlspecialchars($_GET[\'app\'])){echo ?

The following steps are described for one virtual machine containing if(htmlspecialchars($_GET[\'app\'])){echo inside one mirror module. Each replicated virtual machine runs in an independent mirror module (with a maximum of 32 virtual machines) with a primary server that can be either the Hyper-V server 1 or the Hyper-V server 2.

Step 1. Real-time replication

Server 1 (PRIM) runs the VM (virtual machine) containing if(htmlspecialchars($_GET[\'app\'])){echo . SafeKit replicates in real time the VM files (virtual hard disk, VM configuration). Only changes made in the files are replicated across the network.

Synchronous replication in a Hyper-V cluster with if(htmlspecialchars($_GET[\'app\'])){echo

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 if(htmlspecialchars($_GET[\'app\'])){echo 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.

Failover in a Hyper-V cluster with if(htmlspecialchars($_GET[\'app\'])){echo

The failover time is equal to the fault-detection time (set to 30 seconds by default) plus the VM reboot time. 

Step 3. Automatic failback

Failback involves restarting Server 1 after fixing the problem that caused it to fail. SafeKit automatically resynchronizes the VM files.

Failback in a Hyper-V cluster with if(htmlspecialchars($_GET[\'app\'])){echo

Failback takes place without disturbing the VM containing if(htmlspecialchars($_GET[\'app\'])){echo , which can continue running on Server 2.

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 if(htmlspecialchars($_GET[\'app\'])){echo running on Server 2 and SafeKit replicating file updates to Server 1.

Return to high availability in a Hyper-V cluster with if(htmlspecialchars($_GET[\'app\'])){echo

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.

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 High Availability Differentiators