There has been a bit of confusion recently over the use of OEM ESXi ISO images and Virtual SAN. These OEM ESXi ISO images allow our partners to pre-package a bunch of their own drivers and software components so that you have them available to you immediately on install. While this can be very beneficial for non-VSAN environments, it is not quite so straight-forward for VSAN deployments. Drivers associated with VSAN have to go through extra testing for some very good reasons that I will allude to shortly. The issue really pertains to the drivers that are shipped with many of these ESXi images; in many cases these are the latest and greatest drivers from the OEM for a given storage controller and may not yet be qualified for VSAN (qualified == tested).
Does it matter that they haven’t been specifically tested for VSAN? Sure it does. We need to make sure that we can do specific VSAN operations on the drives, such as hot-plug replacement, etc. Also, we need to ensure that the performance isn’t degraded by an introduction of a new driver. In the past with local storage, this was probably not such a big deal. But when local storage now contributes to a distributed storage platform like VSAN, it matters a lot. So this is why drivers associated with VSAN have to go through extra testing.
We understand that this is a bit of a drag for many of you who use these OEM images, because it means you now have to go back and downgrade the driver for a given storage controller back to a version that is supported by VSAN, as per the VMware Compatibility Guide (VCG). Unfortunately, there is not a lot we can do about this at the moment if you wish to continue using these OEM images.
What are we going to do about it going forward? Well, the good news is that we are creating a test suite for our partners’ storage controllers, and as our partners start to ramp up their testing to include this suite (probably in 2015 at this stage), we should begin to see these OEM ESXi ISO images appear with VSAN-qualified drivers.
But for now, always check the VCG to make sure that your storage controller model, driver and firmware version are all at a supported level.
[Updated: 29 Nov 2016] I was asked whether OEM versions of ESXi were still valid with vSAN 6.5 and vSphere 6.5. The answer from the vSAN PM team was yes – OEMs should be shipping these images with drivers supported with vSAN. If any drivers are out of date, the vSAN health check will catch it. The only real difference between the standard image and the OEM image is that OEMs include custom tools and utilities for management, CIM provider etc.