Disaster Recovery vs Disaster Avoidance

One thing is for sure, that you cannot mix disaster recovery for disaster avoidance; both are separate even though it sounds similar.

Let’s try to understand the difference between these concepts using VMware Stretched clusters and VMware Site Recovery Manager.

Stretched clusters consist of two or more physical ESXi hosts deployed in separate sites that are less than 100 kilometres apart and are contained within a single vSphere cluster. This simply means that a VMware cluster of several hosts located at different sites using the same vCenter server.

By using Stretched cluster you can vMotion a VM from one site to another without any downtime, that’s Disaster Avoidance – A solution where  you cannot afford to have minimal downtime for your DR solution. In short it’s a very good Active site balancing solution.

In case of VMware SRM, the VM would start at the recovery site when the storage snap is attached to it by a sequence of automated scripts. Now this is a solution which would require the restart of the VM, hence downtime is mandatory. That’s a normal Disaster Recovery situation. Moreover you would require two vCenter servers for your SRM DR solution.

Now, let’s see the difference in a tabular format

However it’s important to note that both the solutions have their benefits according to the requirement. Both solutions enhance service availability, while stretched clusters focus on data availability and service mobility Site Recovery Manager focuses on controlled and repeatable disaster recovery processes to recover from outages.