http://pubs.vmware.com/vsphere-50/index.jsp?topic=/com.vmware.vsphere.storage.doc_50/GUID-F78EB579-B11C-4E65-9EE3-145888A005F6.html

This describes how to setup the vSphere side of things for a mirrored disk within a Windows 2008 Guest. Just imagine doing in-guest mirroring of your data while doing FT on the outside. This means you would be able to span multiple sites without the need for a replication mechanism.

I asked around and unfortunately this scenario is not supported today for vSphere FT, but it definitely has potential… Another way to solve this problem would be if we could somehow leverage the Mirror Mode driver that is used by Storage vMotion today. Once again, this is not available today and I don’t even know if people are working on it… just something that popped up and something that has great potential and seems like a small step.

The Design and Evaluation of a Practical System for Fault-Tolerant Virtual Machines

There are many possible ways to attempt to detect failure of the primary and backupVMs. VMware FT uses UDP heartbeating between servers that are running fault-tolerantVMs to detect when a server may have crashed. In addition, VMware FT monitors thelogging traffic that is sent from the primary to the backup VM and the acknowledgmentssent from the backup VM to the primary VM.

Please take the time to fill out the survey and help VMware to improve FT and HA! It will only take a couple of minutes: http://www.surveymethods.com/EndUser.aspx?AD89E5F7ABEEFDF8

This survey will collect information relevant to VMware Fault Tolerance and VMware HA, a new solution that shipped with VMware vSphere 4. VMware Fault Tolerance provides 100% uptime for a VM in the course of an ESX host failure. This feature will ensure your VM continues running without data loss or noticeable downtime should you encounter a single host failure. As we continue to advance this solution, we hope you can provide us information about your current deployment that will help us design Fault Tolerance and HA with your most missions critical VMs in mind.

As you can imagine the HT requirement for FT has been floating around ever since and is a myth which have never been debunked. I’ve spoken with product management about it and they confirmed it’s an obsolete requirement. Hyperthreading does not have to be disabled for FT to work. Or to put it even more strongly: FT is supported on systems which have hyperthreading enabled. Product Management promised me that a KB article will be created to debunk this myth or an entry will be added to the FT FAQ KB article soon.

UPDATE: The FT FAQ KB Article has been updated and includes the following statement.

Does Fault Tolerance support Intel Hyper-Threading Technology?
Yes, Fault Tolerance does support Intel Hyper-Technology on systems that have it enabled. Enabling or disabling Hyper-Threading has no impact on Fault Tolerance.

The CPU scheduler in VMware ESX 4 is crucial to providing good performance in a consolidated environment. Since most modern processors are equipped with multiple cores per processor, systems with tens of cores running hundreds of virtual machines are common. In such a large system, allocating CPU resource efficiently and fairly is critical. In ESX 4, there are significant changes to the ESX CPU scheduler that improve performance and scalability. This paper describes these changes and their impact. This paper also provides details of the CPU scheduling algorithms in the ESX server.

I can elaborate all I want but I need you guys to read the whitepaper to understand why vSphere is performing a lot better than VI 3.5. (I will give you a hint: “cell”.)

Another whitepaper that’s definitely worth reading is “Virtual Machine Monitor Execution Modes: in VMware vSphere 4.0“.

The monitor is a thin layer that provides virtual x86 hardware to the overlying operating system. This paper contains VMware vSphere 4.0 default monitor modes chosen for many popular guests running modern x86 CPUs. While most workloads perform well under these default settings, a user may derive performance benefits by overriding the defaults. The paper examines situations where manual monitor mode configuration may be practical and provides two ways of changing the default monitor mode of the virtual machine in vSphere.

And while you arealready taking the time off to educate yourself you might also want to read the “FT Architecture and Performance” whitepaper. Definitely worth reading!

Description: Managing VMware Fault Tolerance via the command line.

Params: The following operations are supported: create|enable|disable|stop

Requirement:
vSphere vCenter 4.0
ESX(i) 4.0
Advanced, Enterprise, Enterprise Plus or Eval licensing

Assumption: Your environment is FT capable and is configured properly

I think it speaks for itself. If you are a command line guy this is really useful! Great work William, keep it up! Just head over to the VMTN Communities for the download link and more details on how to use it.

Marathon FT and VMware FT

a short outtake: “This wasn’t talked about but Marathon’s virtualization FT only works with Windows 2003 Standard or Enterprise SP1 today. VMware FT works with any of the over 70 certified guest operating systems that run on Virtual Infrastructure. The Marathon solution also sits deeply embedded within the OS.”

Marathon everRun vs VMware HA – Another Mess

a short outtake: “As you can now see, Marathon obviously has never touched a VMware host to setup VMware HA. They simply type what they want customers to hear on their webpages time and time again and rely on that FUD to get them sales.”