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:
|VM HA with SafeKit||Application HA with SafeKit|
|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 failover||Application 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 / OS||Integration per application|
|Microsoft Hyper-V Cluster & VMware HA||SafeKit with Hyper-V 2012 R2|
Simple and economical solution
|Shared disk and specific bay of disk||No shared disk|
|Remote sites = replicated bays across a SAN||Remote sites = no replicated SAN|
|Enterprise Editions of Windows and VMware||Works with|
|Specific IT skills to configure the system||No specific IT skill to configure the system|
|Large number of VMs||Limitted number of VMs (25 VMs)|
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.
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.