VM HA vs Application HA

VM HA implements high availability at the virtual machine level, while Application HA implements high availability at the application level.

We start this article with the example of an Application HA cluster (Microsoft SQL Server 2012) and with the example of a VM HA cluster (Hyper-V). Both clusters have been implemented with real time replication and failover of the SafeKit software.

Then, this article examines:

Example of an Application HA cluster: Microsoft SQL server 2012 with real-time replication and failover

More information on how SafeKit works with other applications on Windows, Linux and AIX here...

Example of a VM HA cluster: Hyper-V cluster with real-time replication and failover

More information on how SafeKit implements a Hyper-V cluster here...

VM HA vs Application HA

VM HA with SafeKitApplication HA with SafeKit
Application HA
Replicates too much data (App+OS)Replicates only application data
Reboot of VM if crash (recovery time)Quick restart of App on OS2 if crash of VM1
No application checker and software failoverApplication checker and software failover
Risk of downtime when fixing OS or App (single image)Smooth upgrade of OS1 or OS2 or App (two images)
Generic solution for any application / OSIntegration per application

SafeKit vs Microsoft Hyper-V Cluster & VMware HA

Microsoft Hyper-V Cluster & VMware HASafeKit with Hyper-V 2012 R2
Simple and economical solution
SafeKit with Hyper-V 2012 R2
Shared disk and specific bay of diskNo shared disk
Remote sites = replicated bays across a SANRemote sites = no replicated SAN
Enterprise Editions of Windows and VMwareWorks with

  • the free edition of Hyper-V 2012 R2
  • Hyper-V integrated in Windows 2012 R2
  • Hyper-V integrated in Windows 8.1
Specific IT skills to configure the systemNo specific IT skill to configure the system
Large number of VMsLimitted number of VMs (25 VMs)

Application HA in or outside the Cloud with SafeKit

In or outside the Cloud, SafeKit offers

This is an essential feature for a software publisher which deploys its application in heterogeneous environments. The high availability of its application must work on physical servers, in VMware environments (with or without the VMware HA option), in Hyper-V environments (with or without the Microsoft cluster option), in other hypervisors...

For instance, today we have a generic solution for deploying in or outside the cloud  the Evidian Web Access Manager application with SafeKit load balancing, real-time replication and failover.

Contrary to Microsoft NLB, SafeKit network load balancing works without any special configuration in VMware.

VM HA in the Cloud with SafeKit

SafeKit offers a simple and economical solution to build a private cloud with

This solution works with the free edition of Hyper-V 2012 R2. The architecture does not require a shared disk or a replicated SAN if the two servers are in two remote computer rooms.

A video of  an Hyper-V cluster with load balancing, replication, HA and failover built with SafeKit demonstrates this architecture.

Note that this architecture does not work with VMware ESXi because SafeKit cannot be installed in the VMware hypervisor.

More comparisons to understand how to achieve simplicity in high availability


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