Virtualization: March 2014

In this post i will discuss and configure VMware fault tolerance (FT). FT provides continuous availability for a virtual machine, it means if a virtual machine is running on a physical host and that physical host is suddenly down completely and if a virtual machine is protected by fault tolerance, it will have a shadow virtual machine running on another physical host and that virtual machine has a zero downtime. FT takes VMHA to next level. In HA cluster, if a host is down the virtual machine will have to be restarted on another host. In FT the virtual machines are always running no matter what if a physical host is completely lost. FT uses VMware's lockstep technology.
With VMware FT the primary virtual machine is called "Primary" and the copied/lockstep virtual machine is called "Secondary". The virtual machine disk files remain on shared storage.

Requirements:
1- Minimum of vSphere Enterprise license.
2- CPUs of all servers must match and be from a specific list of processors that FT supports.
3- Minimum of 3 NIC of 1GB are recommended. One for management, one for vMotion and one for FT logging.
4- Shared storage present on each host.
5- VMware High Availability cluster must be enabled.
6- Virtual machine's disk must be of thick eager zero type.

Configuration:
I have already installed ESXi 5.1 on two host and a shared storage is also presented on the host. A virtual machine is created on shared storage. Since Ft requires vMotion and High Availability. I have configured both the features. There are separate posts for both vMotion and VMHA configuration in the blog.

1- I have also setup my network according to VMware FT best practice. I have assigned separate NIC for management, vMotion and FT logging. Perform the same network configuration on each physical host.

2- In order to fulfill Fault Tolerance per-requistics, VMware has a free tool named "Site Survey". The tool is available for download from VMware website. I have downloaded and installed the tool and now is appears as a tab in vSphere client. Select Run SiteSurvey.

3- Select Run.

4- The tool will generate a detailed report. Read the report and resolve the issue related to FT. I have resolved all the FT issues.

5- Now select the virtual machine on which the fault tolerance is going to perform. In my lab environment, I have virtual machine named “SRV”. Right click the virtual machine and select "Turn On Fault Tolerance" under Fault Tolerance.