This is the distinguished name of a memory buffer unit object, a registering clock driver/buffer chip that sits on certain buffered DIMM or riser designs to fan out memory signals to more DIMMs per channel. An admin follows this Dn to locate a specific buffer chip when troubleshooting a memory array that uses buffered DIMM technology, since a buffer chip fault can take out access to multiple DIMMs behind it at once. A Dn like sys/chassis-1/blade-3/board/memarray-1/bufferunit-1 identifies the first memory buffer unit on that blade's first memory array.