It probably is not an R/RW drive. They were very uncommon in the 2950, particularly when they first came out.
If I try to burn a Dell diagnostics DVD, I get drive is not ready. Can read from DVD. Can eject the DVD. If I use Windows to look at a blank DVD, all categories are 0 bytes Have updated to the latest Dell diagnostics and all the drive tests pass. I tried to update the BIOS from 2.6.1 to 2.7.0 and get the program could not collect the BIOS version Had Windows look for a updated driver and Windows says best driver is installed. 
PowerEdge 2950 Can not write to DVD drive