ESXI can be installed on local, san ( iSCSI, FCOE, FC) , USB and on stateless (PXE type). I find out the installation method in the following way. ( there could be many other easier ways)
1. SSH to the machine
2. type "ls -l /"
3. Find out the location of /bootbank from above command output. It will be something like " bootbank -> /vmfs/volumes/70a79c7d-d52a965b-5fa9-4b7ce9267870"
4. Do "vmkfstools -Ph /vmfs/volumes/70a79c7d-d52a965b-5fa9-4b7ce9267870"
5. In the output of above command, it will give a naa.xxxxx:6 name ( something like naa.600508b1001c76e264f43c38b3d5c4f7:6)
6. Do "esxcfg-scsidevs -c |grep -i naa.600508b1001c76e264f43c38b3d5c4f7
From the output of the above , it will tell from which disk the esxi is currently booted. Based on the disk name you should be able to tell if it is local or san.
