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Tag Archives: Fault Tolerance

Thank you for still reading my blog. I just had a chance to build a FT VM lab. I record some potential issues and how to resolve the problem. I hope it will help you to understand FT.

Quote the VMware FT compatibility Requirements:

Identify VMware FT compatibility requirements

  • Same Build number for ESX(i) hosts
  • Gigabit NIC’s
  • Common Shared Storage
  • Single Proc machine
  • Thin Provisioned disks not supported (automatically converted)
  • No snapshots

Lab Environment

I have following hardware as my lab equipment.

2 identical HP server. 6 Nics on the server. 1 Test VM running W2K3R2 x64bit.

Test VM has 1 vCPU.

All right. We all set. Let’s see what we can do.

Turn on Fault Tolerance

If you got all your configuration right, all what you need to do is to right click your VM and choose Turn on Fault Tolerance.



However, you may got following errors.

Typical Errors


1.No FT VMkernel



FT requires to use specific Network to make sure logs will be copied from Primary VM to Secondary VM. You need to either create a specific VMkernel or use the exist one. In my case, I use my vMotion network since I know I don’t vMotion much.





2. Insufficient resources for HA



The FT requires HA to be enabled. However, with my scenario, I only have 2 hosts and HA enabled. The Host failure cluster tolerate is 1 host. FT won’t accept that. The easiest way is to use percentage of resrouces and setup it as 5%.



3. Thin disk need to be converted to thick



This is a test lab. The is no double I use thin disk for this test VM. so FT doesn’t work on thin disk and it has be converted to thick.


Power off test VM. Go to that VM from datastore broswer and right click the vmdk. Choose “Inflate”



Then, it should work!



Few tips for FT. FT is very powerful. I have running ping test from test VM and power off the primary host. No ping was dropped!. But it does generate heaps of traffic on FT log vmkernel (33MBPS). so Please be aware don’t put too much pressure on your network.

Have fun.