I was listening to an very interesting presentation this evening from Olivier Cremel, Principal Engineer
ESXi Internals: Better Understanding for Better Management and Troubleshooting

The ESXi Architecture document actually states that the memory footprint of the hypervisor is 32mb

Eric Gray, also put up a post regarding the hypervisor footprint - again 32mb

The hypervisor is loaded into memory into a RAMDISK. But where exactly can you see the size of the RAMDISK in which the hypervisor runs, and is it actually 32mb?

Two places:

1. In the System Resource Allocation settings for your ESXi host.

Here you can see that the size of 32MB is reserved - so that it will always be available - but it is also limited at 32MB so that it does not grow larger than the specified size.

2. In the ESXi host itself.

As you can see from the output below

~ # vdf --help
vdf: invalid option -- -
Gather stats about visorfs
visorfsdf [filepath]
   -h       multiple instead of blocks
   -p       resource pool view

As you can see from the output above the MAINSYS partition is the set 32MB.

Of course because all the entities above are resource pools, they can be configured to your needs - but they should only be done with specific guidance from VMware support.

A nice bit of info..