VMware publishes a guide called the Hardware Compatibility List (HCL). The HCL lists all of the hardware components that are supported by each version of ESX and ESXi. This very important guide is divided into different sub-guides, which include systems (server make/models), storage devices (SAN/iSCSI/NFS) and I/O devices (NICs/atorage controllers), and is updated frequently with new hardware added and older hardware removed. I was curious about the inner workings of how this guide is maintained, so I contacted VMware for some answers.
First, you might wonder why this guide is important? There are two reasons. The first is that ESX/ESXi has a limited set of hardware device drivers that are installed and loaded into the VMkernel, and while it is possible to install additional unsupported device drivers, it is not recommended. Consequently, if you use a network or storage adapter that is not on the HCL, there is a very good chance that it might not work because the driver for it is not included.
The second reason is that VMware only provides support for server hardware that is listed on the HCL. Just because server hardware is not listed on the HCL doesn’t mean it will not work with ESX/ESXi, however. There is a lot of older hardware and other hardware brands/models that are not listed on the HCL that work just fine but are not supported by VMware. So if you are using hardware that is not listed on the HCL and call VMware’s Global Support Services for assistance with an issue, you might wonder if they will help you at all. What VMware will do is assist customers in problem analysis to determine whether or not the issue is related to the unsupported hardware. If the issue is suspected to be hardware-related, VMware reserves the right to request that the unsupported hardware be removed from the server. If VMware determines that the problem is related to the unsupported hardware, they will request that you open a support request with the hardware vendor instead.
So you might be wondering how the hardware on the guide is selected? Hardware vendors have to test and certify that their hardware works properly with the latest versions of ESX and ESXi. Once this has been completed, VMware will add them to the guide. VMware works with hardware vendors as part of their Technology Alliance Partner (TAP) program, and any vendor can apply to have its hardware added to the HCL. Once an application is received, the vendor is responsible for completing the certification criteria and submitting its results to VMware for review and approval. The first step of this process requires vendors to submit a VMware Compatibility Analysis for the hardware that they intend to certify. After VMware reviews and approves the analysis, the next step is for the vendor to engage with a third-party testing lab (currently VMware works with AppLabs or Cognizant for this) to certify that its hardware works properly with ESX and ESXi. VMware will not disclose the specific testing criteria that is used for certifying hardware for the HCL, but it does use the same certification criteria for all vendors that apply.
You’ll probably notice that the HCL contains mostly newer hardware and that older hardware is periodically removed from it. VMware does not enforce an expiration period for hardware added to the HCL, but it is up to each vendor to certify its hardware for the most current VMware product releases. Vendors are free to initiate the certification process at any time it needs to have new hardware added to the HCL. Additionally, each vendor can choose to remove older hardware from the HCL as it releases newer hardware versions.
So while using hardware not listed on the HCL may be OK for labs, it is highly recommended that you only use hardware on the HCL for production use. Be sure to check the HCL periodically, especially if you plan to upgrade to a newer ESX/ESXi version, as you will want to make sure your hardware is listed before upgrading. You should check this guide before you purchase any server hardware to use with ESX/ESXi. Also, be sure all your server components are listed in the guide, including NICs and storage adapters. Often it may take a short period of time before newer hardware is added to the HCL. If you have newer hardware and it is not yet listed on the HCL, try contacting the vendor to see where it is at with getting its hardware certified by VMware.
The guide format was recently changed and is now searchable via an online form. Additionally, you can download the full guides in PDF format for each hardware component. Make sure you bookmark the guide and periodically check it — you don’t want to find out when you call VMware support that you’re using unsupported hardware.
Special thanks to John Troyer, who got me in touch with the right person at VMware to talk to, and to Nick Fuentes, who found the answers to my questions.