Understanding ESX/ESXi Equivalency…Are we there yet?

So I am often asked the question “how does this work in ESXi?” from my customers, especially around HW or management agents equivalency. So I hope to make the answer a bit more clear for everyone…

It is public knowledge that ESX is evolving to a pure ESXi model in the future release cycles of the product, though exact timelines are still under NDA. Convergence to a “console-less” ESX provides a number of benefits to our customers, with which many of you are, by now, well acquainted . It reduces the overall footprint that requires patching (see below) as well as removes the dependency on the vestigial RHEL-based Console Operating System, and sets the stage for future enhancements and technologies yet to be introduced. (Those who are under NDA might know to what I am referring!) 🙂


At any rate, as we march toward a converged ESXi model, it is important to understand that while the evolution to ESXi is still underway, VMware (and it’s ecosystem partners), are really starting to deliver equivalent functionality between a COS based ESX and ESXi. You will soon see another step along this journey when we have our next major release (TBA!). When we do release the next GA of ESXi, I will post a follow up to this article detailing the new features and highlights of ESXi v.X. For now however, let me point out a couple of overall messages on the topic…


There are clear, direct paths from ESX to ESXi as illustrated above. Management agents now become vAPI (generally direct SOAP api) calls, HW agents now rely on the standards-based CIM (Common Information Model) instrumentation, command interfaces are now vCLI and PowerCLI based leveraging assists like the vMA (Management Appliance), and the ISAs become “native” to ESXi along with the DCUI (Direct Console User Interface)

In terms of partner ecosystem preparedness, here is a partial product and version list from March, 2010, of those systems management and backup partners who are ready for ESXi today…



Finally, I thought I would share the list of common mis-conceptions that have been brought up in customer meetings, and the associated current realities about ESXi.


One thing not on the above list is the confusion by some about the differences between ESXi embedded and installable. Besides the basic fact that embedded ships already integrated into the server from the OEM vendor in some manner (on SD, USB, etc) and contain the CIM monitoring and health agents from said OEM, and installable is installed on local disk, many ask about “What If” scenarios like unplugging the USB key from a booted ESXi host on embedded or a local hard drive crash on installable. The fact is, that the system is completely memory resident, no matter from where it was booted (USB, CD, disk, PXE, etc.), and though the config is saved back to the boot partition, losing access to it just means the config is not updated dynamically…the VMKernel still runs. Also, the logs are configured to go to local storage by default, but you have the option to redirect these to a network log server. Some of these details (and others), are covered in the ESXi Chronicles, a VMW Community blogsite. http://blogs.vmware.com/esxi/

So make no mistake, I am not saying we are fully “there” today with a complete replacement of ESX with ESXi in all aspects, but if you are not testing or working with ESXi today as of yet, I highly encourage you to do so. Start learning vCLI and PowerCLI, they can be invaluable in your management strategy. Check out your partner backup and systems management products to ensure that they have ESXi compatible versions and integration points. Start looking into a plan for migration over time so that by the time VMware is there with an pure ESXi version of vSphere, you can be ready as well.

  1. Good post. I still see way too many people that think ESXi is VMware's free and limited hypervisor.

  2. Still, one difference is that ESX supports jumbo frames (setting the MTU on the vswitch), while ESXi does not.

    1. Alessandro,
      The first two might be available, but they were adapted from an internal VMW Engineering preso…the last three I created from information drawn from a couple of other presentations. I can certainly pass along the original slides if you would like them. Just drop me a line at tmackay@vmware.com

Comments are closed.