Find number of unused disk bays on a dell server running windows or ESXi

1. Use the Dell support site to see what the configuration of the shipped server was by inputting the service tag (get the service tag remotely wmic bios get serialnumber )

2. Connect to the out of band management controller (iDrac)

3. Run racadm hwinventory

4. Use Open Manage Server administrator

5. talk to the pci bus lspci and talk to the bios dimidecode

in the end it will be a mixture of knowing what hardware you have and with what options (daughter cards, mezzanines, SAS expander) then simply listing the physical disks pvs or wmic diskdrive list brief R730's can hold up to 8 as a max by default and up to 16 in the drive bay and inside the chassis.