Begin your investigation with ...
format
iostat -En (Solaris 8 and newer)
You can use both of those commands and get most of the information you want.However if the drives are in an external array, you may only be shown the array controller, because that hardware controller does additional filesystem-per-disk translation.
If you are using Volume Manager, Disksuite, or 3rd party disk software (EMC?, StorageTek?, HP?, IBM? ... whatever) then you may need to review the documents for those software suites.