I received a question today from someone who wanted to know the difference for isolation detection between vSphere 5.0 and 5.1. I described this in our book, but I figured I would share it here as well. Note that this is an outtake from the book.

The isolation detection mechanism has changed substantially since previous versions of vSphere. The main difference is the fact that HA triggers a master election process before it will declare a host is isolated. In this timeline, “s” refers to seconds. The following timeline is the timeline for a vSphere 5.0 host:

  • T0 – Isolation of the host (slave)
  • T10s – Slave enters “election state”
  • T25s – Slave elects itself as master
  • T25s – Slave pings “isolation addresses”
  • T30s – Slave declares itself isolated and “triggers” isolation response

For a vSphere 5.1 host this timeline slightly differs due the insertion of a minimum 30s delay after the host declares itself isolated before it applies the configured isolation response.

--> Please see the rest on the blog : http://www.yellow-bricks.com/2012/12/31/isolation-detection-in-vsphere-5-1-versus-5-0