you may try the commands in ESXi console:
1. #esxcli system boot device get //get boot device's UUID
2. #vmkfstools -Ph /bootbank //record device info under "Partitions spanned (on "disks"):", I got "mpx.vmhba34:C0:T0:L0:6"
3. #esxcli storage core device list -d <device info recorded in last step, without the latest partition number and ":" > |grep Model // in my case input is "mpx.vmhba34:C0:T0:L0"
Then you can get the boot device Model, you will know which device you boot from
