PowerEdge R520 mixed memory configuration

Question

Hello, I have a dual-processor PowerEdge R520, and I want to upgrade the memory, while retaining as many of my existing DIMMs as I can (all, preferably!). It currently has 32GB in 8x 4GB ECC DDR3 RDIMMs,1333MHz low volt single rank (Dell-331-4422). I'm looking at adding 2x 16GB ECC DDR3 RDIMMs, 1333 MHz  low-volt dual rank, PC3-10600. The R520 has three memory channels per processor, supporting up to 12 DIMMs I'm looking at the document ps2q09-20080414-Benson.pdf regarding Dell R520 memory configuration, but it's not clear to me how I should plan to configure the memory modules I have, or whether this upgrade is a good choice. Can I mix 16GB and 4GB DIMMs in the same channel? Which channel should use the larger DIMMs? Should I plan to purchase all new DIMMs if I want to increase the memory to 64GB? Can you advise? Thanks!

Daniel My · Accepted Answer

A1,A2,A3,B1,B2,B3 = 8GB DDR3 1600Mhz ECC RDIMM (low volt, single or dual??)

A4,A5,A6,A7,B4,B5,B6,B7 = 4GB DDR3 1333Mhz ECC RDIMM (low volt, single rank)

for a total of 80GB of RAM.

It would be 72GB, there is no slot 7. There are 6 slots on each lane.

I can purchase 8GB modules as either single or dual rank, with all other features being equal. In combination with all those single rank 4GB DIMMs, would single or dual be preferable? Does it matter?

The rank will not matter unless you get quad rank DIMMs. If you get quad rank modules you may not be able to use all of the slots. I would have to check the population rules regarding quad rank modules to be sure.

A1,A2,A3,B1,B2,B3 = 8GB DDR3 1600Mhz ECC RDIMM (low volt, single or dual??)

They can be single or dual, but all memory within a bank should be identical, including rank.

Thanks

Daniel My · Answer

Hello

To simplify this I'm not going to explain B lane population. Both lanes should have identical memory configurations, so whatever you put in A should also be in B.

There are three channels and two banks. Memory can be mixed within a channel, but all memory within a bank should be identical. The R520 supports flexible memory configurations, so you may be able to mix memory in various ways that will work. The best configuration would be:

4GB modules in 1,2,3
16GB modules in 4,5

You will need two more 16GB modules to populate in the B lane. You can try putting a single 16GB DIMM in slots for on both lanes, it will likely work, but memory should be installed in pairs at a minimum.

Higher rank modules are supposed to be installed first, but I don't think that is an enforced population rule. If you follow all of the population rules then there is no supported configuration to populate the 16GB modules since you only have 2. If you had 4 the supported configuration would be:

16GB modules in 1,2
4GB modules in 4,5

You can't populate slots 6 unless a module is in slot 3. If you purchased 6x16GB modules then you can populate:

16GB modules in 1,2,3
4GB modules in 4,5,6

Thanks

Library_IT · Answer

I see. Thank you. That makes the principles more clear.

So it should be a superior configuration to purchase the following:

Crucial CT3361993 - 6x 8GB DDR3-1600 ECC RDIMM low-volt

and populate the channels as following:

A1,A2,A3,B1,B2,B3 = 8GB DDR3 1600Mhz ECC RDIMM (low volt, single or dual??)

A4,A5,A6,A7,B4,B5,B6,B7 = 4GB DDR3 1333Mhz ECC RDIMM (low volt, single rank)

for a total of 80GB of RAM.

Is that a good configuration?

I can purchase 8GB modules as either single or dual rank, with all other features being equal. In combination with all those single rank 4GB DIMMs, would single or dual be preferable? Does it matter?

Thanks!

Library_IT · Answer

Thanks for the information.

I purchased 8x 8GB single rank modules, and replaced all the 4GB memory, for a total of 64GB. I'm re-purposing all the 4GB DIMMs in a set of HP Proliant ML350 G6 servers, in which the 1.35v DIMMs are compatible.

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