Current configuration: 4x64GB LRDIMM, 2400MT/s, Quad Rank, x4 Data Width
We have a lot of these available: 32GB RDIMM, 2400MT/s, Dual Rank, x4 Data Width
My question: Will we see a negative performance impact when switching from 256GB (total per server) Quad Rank LRDIMM to 384GB (total per server) Dual Rank RDIMM?
No, you will not see a negative performance impact in your case.
RDIMM memory modules perform slightly faster than buffered LRDIMM modules, assuming they are of the same speed rating. It will vary based upon workload, but you can expect to see around a 5% performance difference in the real world.
The advantage to using LRDIMMs is that you can install double the memory in the server, as you can when using RDIMMs. 24x32GB modules for a total of 768GB, compared to 24x64GB modules.
Remember that you cannot mix LRDIMMs and RDIMMs in the same system.
