Is it software RAID or hardware RAID?
Looking at the spec sheet of PowerEdge T30, it is Intel Software RAID unless you added a hardware RAID card.
If it's hardware RAID, you have to check if the RAID controller is in the Compatibility Guide (which means a VIB is available even in the standard image). I don't see the T30 in the Compatibility Guide.
http://www.vmware.com/resources/compatibility/search.php?deviceCategory=io
Alternatively, you can try to install the ESXi hypervisor on a USB thumb drive (4GB thumb drive will be sufficient). You will then boot up the ESXi hypervisor from the USB thumb drive and configure the storage present in the T30 as your VMFS datastore.