Noctua's DX line of coolers has become a default choice in high performance quiet cooling solutions for Intel Xeon CPUs. The i4 revision supports LGA2011 (both Square ILM and Narrow ILM), LGA1356 and LGA1366 based Xeon platforms and the new D9 model provides better performance and better compatibility than previous 9cm versions: Thanks to its 95x95mm footprint and reduced 110mm height, the NH-D9DX i4 is fully 3U compliant and clears the RAM slots on LGA2011 Square ILM and LGA13xx. At the same time, the dual tower design and the new NF-A9 PWM guarantee further improved quiet cooling performance. Fitted with the professional SecuFirm2 mounting system and bundled with Noctua's industrial-grade NT-H1 thermal compound, the NH-D9DX i4 3U forms a complete premium quality package for quietly cooling Xeon based workstations and servers.
Pros: Quiet. Keeps a i7-5930K @ 3.5GHz at 40-41C with virtually no audible noise at idle. Installation is nice--there are vertical holes all the way through the cooling fins at each corner, and they provide a long hex driver that extends down through the holes to engage the mounting screws, so no access at all from the side is required to get the thing on or off even for the "square" hole pattern where you usually have to get under the cooler to get to the mounting screws. Removing and replacing the fan would be trivial even with the unit in place--remove two wire clips that engage the heat sink fins, and pull the fan out vertically.
Cons: It's $60 for a $5 fan and a couple of pieces of metal, but hey, it's keeping a $600 CPU from melting down, so I guess that's not really a con. The fan is this peach-and-brown color scheme like the furniture in a 1970s singles bar, which if it's laboring away in the dark is no problem, but if you're building a flashy gaming rig in a case with a lot of windows, you may want to replace the fan with something more decorative.
Overall Review: It is set up to work with the "square ILM" hole pattern. It comes with two sets of brackets which convert it to the "narrow ILM" hole pattern (the one where the mounting screws are at two ends of the CPU footprint rather than at the corners). In either case it can be mounted so as to get airflow in any one of the four directions.