Your system supports DDR3 ECC unbuffered memory modules (UDIMMs). The DIMMs can be 1066 or 1333 MHz. Single and dual-rank DIMMs can be 1066 or 1333 MHz.
http://www.memoryupgrade.pro/
http://www.memoryupgrade.pro/dell-memory-poweredge-memory-poweredge-t110.html