Struggling with this here, pulling my hair out!
I have a gigabit network and i'm struggling to achieve (semi) gigabit speeds. I have ESXi 5 with only Windows Home Server 2011 running as a VM so far. I seem to be able to download from WHS at around 80MB/s which is fine but if i upload, I can only manage speeds of around 10, 20-25 MB/s.
I've added the VMXNET3 adapter and installed/upgraded VM Tools and still having the same issue.
Without ESXi in the equation, i was acheiving gigabit speeds.
Welcome to the Community,
according to the hardware specs you mentioned in Struggling with Hard Drive setup... this could be an issue with the disk performance. ESXi does not do any disk caching and fully relies on the system's (usually RAID controller's) capabilities. Without write-back mode - with e.g. a RAID controller with BBWC/FBWC - you may be limited to the write speed you currently see.
Not sure if this is it, but here's an idea: WHS 2011 only allows one processor. You can have more than one core, just not two processors. There's quite about this written on the internet, so you might check out the work-arounds.
What I am thinking is that your WHS 2011 may only be running on one core. You can do some tweaking to tell it that it only has one virtual processor and then designate 2 or 4 cores. It's an idea. Here is a link that has a pretty good writeup on this. http://communities.vmware.com/thread/335733 .
Hope this helps.