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We are buying new Dell R410 servers, and I'm trying to figure out the best RAM performance we can get.

Dell offers the following choices:

8GB Memory (8x1GB), 1333MHz Single Ranked UDIMMs for 2 Processors, Optimized
8GB Memory (4x2GB), 1333MHz Single Rank LV RDIMMs for 2 Processors, Advanced ECC
8GB Memory (4x2GB), 1333MHz Single Rank LV UDIMMs for 2 Processors, Advanced ECC
8GB Memory (8x1GB), 1333MHz Single Rank LV RDIMMs for Dual Processors, Optimized

From reading Dell help, and the following document: http://www.dell.com/downloads/global/products/pedge/en/server-poweredge-11g-white-paper.pdf

It seems the last configuration will the best performance one - is this correct? Also, is there any real difference between UDIMM and RDIMM for this kind of configuration?

Thanks!

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Trying to find more information on how the 3 x memory controllers on 5500 and 5600 CPUs maps to the 4 DIMM slots per-processor on the R410. I'm guessing it can be configure to either use 2 controllers with 2 DIMMS per controller, or 1 controller per DIMM slot, leaving the 4th slot useless. Anyone know more? –  Chris Thorpe Jul 13 '11 at 12:33
    
Ah found it. In the R410 TechGuide section 6.1 "8 (2/1/1) DIMM sockets". Implying the first memory controller handles 2 of the DIMM sockets. Is 8Gb a specific limit you have? It looks like the best optimization for raw throughput would be 6 sticks of 2Gb each (12Gb), or 6 sticks of 1Gb each (6Gb). That'd be 1 DIMM on each MCH and should allow you to run in 'Optimized' mode. –  Chris Thorpe Jul 13 '11 at 12:39

2 Answers 2

up vote 2 down vote accepted

So as per the comments above and some extra info, I think this is the fastest configuration:

  • RDIMM (see page 8 'High Performance')
  • 3 x 1Gb (or 3 x 2Gb) sticks per CPU (see page 8 'High Performance')

I realize these options won't provide exactly 8Gb RAM, but that amount appears to be an inefficient one for this processor type. Multiples of 3 seem to be the most appropriate.

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Thanks, we would use 9GB, but it seems Dell does not allow such configuration. –  SyRenity Jul 24 '11 at 13:42

The first response from Chris is very accurate. However, while multiples of three is the appropriate methodology for achieving high performance mode there are some finer points. The ranking versus how many DPC (DIMM's Per Channel) makes a difference as well. If you go more than one DPC your 1333Mhz RAM will get auto clocked down to 1066Mhz, based on how many ranks you have per channel.

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