Today my co-worker asked me a question about memory spec on ESXi hosts. There are two types of memory, LRDIMM and RDIMM available on hardware vendor’s list. Which one is best choice?
My understanding is performance of both DIMMs are similar. The only different is capacity. LRDIMM supports higher memory density that RDIMM may not support.
If you regular server refresh plan that you never expand existing hardware, then RDIMM probably the choice. Also RDIMM is significantly low cost than LRDIMM.
If you expand existing hardware instead of refresh hardware, then LRDIMM is the choice since it give you same capacity but reserves few DIMM slots. Another reason is cost per memory operation of LRDIMM is lower than RDIMM.
I have a farm that mixed by LRDIMM and RDIMM ESXi 5.5 hosts. I really don’t see any differencing from performance perspective. If you are running mission critical application on the farm, such as SAP, Oracle, or SQL. Then LRDIMM is always best choice.