You would lose a small amount due to sparring, but in the current layout with the number of dimms you have. It is the only optimal configuration. You would need to add 8 8gb dimms or lose 8 to go with a non-sparring configuration. At 24 dimms it is the only option.
I have recently updated the RAM in one of our R810s with 24 8GB Dual ranked DIMMS for a total of 192GB. Per the manual I populated A1-A6, B1-B6, C1-C6, and D1-D6. The server also has two processors. The server boots fine and sees all of the RAM, however before booting into the OS I receive the following message: "The memory configuration is not optimal.For more information on valid memory configurations, please see the Hardware Owner's manual on the technical support websiteStrike the F1 key to continue, F2 to run the system setup program." Striking F1 will take you into the OS and it too recognizes all of the RAM. Again this was a configuration found in the manual. Have I missed a BIOS setting or is this configuration truly not acceptable.   Thanks,
PE R810 Memory Configuration