When creating a design for our new vSphere 5 environment I found some strange mismatches in supported configurations. Turns out VAAI is supported on VNX and CX4 when used in a vSphere4 environment, but the CX4 has no VAAI support when used in a vSphere 5 environment. VMware suggests disabling VAAI at ESXi level when used with ESXi5 and CX4, but unfortunately this is a per host setting and will also disable VAAI for the VNX, which of course is not desired. I asked the question on twitter and virtualization friend Duco Jaspars jumped in and did some investigation. In his blogpost named “Challenges when upgrading environment with EMC CX4 to vSphere 5 and mixed CX4/VNX environment” he explains how you could disable VAAI for the CX4 only. This great blogpost needs more than just a re-tweet, therefore this blogpost of mine to refer you to Duco’s post. Now go and read it !!!