What is vmkusage?
vmkusage used to be a very nice tool VMware provided (non supported application) that existed for ESX 1.5x and 2.x. In the beginning you had to download it separately from VMware, but since ESX 2.1.0 it was included in the standard ESX install (but not activated).
When ESX 3 was released, a lot of things had changed. VMware also wanted a single point of operation and the performance stats in the Virtual Infrastructure Client had been much improved and was meant as a replacement of vmkusage. The result was that vmkusage was discontinued.
In Virtual Center 2.5u4 a similar service as vmktree was reintroduced as an optional plugin, and this is installed by default in vCenter 4.0. It is not vmkusage (which was perl based), but a java based solution that runs on port 8443 and is accessed directly from vCenter 4.0.
Link for Install Instructions
