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craziefro
6 Indium

R715 Memory Configuration Not Optimal - After Upgrade

Hello everyone,

I have been attempting to find a solution to a memory configuration issue by reading the Hardware Owners Manual, and Technical Guide but am unable to determine what I am doing incorrectly.

I currently have a Dell PowerEdge R715 with 64GB of memory in the following configuration:

Qty 8 HMT31GR7BFR4A-H9 8GB 2Rx4 PC3L 10600R


A1 Memory module slot A1 (white release lever) 8GB 2Rx4 PC3L 10600R

A5 Memory module slot A5

A2 Memory module slot A2 (white release lever) 8GB 2Rx4 PC3L 10600R

A6 Memory module slot A6

A3 Memory module slot A3 (white release lever) 8GB 2Rx4 PC3L 10600R

A7 Memory module slot A7

A4 Memory module slot A4 (white release lever) 8GB 2Rx4 PC3L 10600R

A8 Memory module slot A8

B1 Memory module slot B1 (white release lever) 8GB 2Rx4 PC3L 10600R

B5 Memory module slot B5

B2 Memory module slot B2 (white release lever) 8GB 2Rx4 PC3L 10600R

B6 Memory module slot B6

B3 Memory module slot B3 (white release lever) 8GB 2Rx4 PC3L 10600R

B7 Memory module slot B7

B4 Memory module slot B4 (white release lever) 8GB 2Rx4 PC3L 10600R
B8 Memory module slot B8

 

When I attempted to add an additional 64 GB of memory (by adding Qty. 4 SNP20D6FC/16G
16GB 2Rx4 PC3L 12800R) in the BELOW configuration I received the “Memory not optimal” error at bootup. I was still able to boot the server, but had to acknowledge the error to proceed.

 

A1 Memory module slot A1 (white release lever) 8GB 2Rx4 PC3L 10600R

A5 Memory module slot A5 16GB 2Rx4 PC3L 12800R

A2 Memory module slot A2 (white release lever) 8GB 2Rx4 PC3L 10600R

A6 Memory module slot A6 16GB 2Rx4 PC3L 12800R

A3 Memory module slot A3 (white release lever) 8GB 2Rx4 PC3L 10600R

A7 Memory module slot A7

A4 Memory module slot A4 (white release lever) 8GB 2Rx4 PC3L 10600R

A8 Memory module slot A8

B1 Memory module slot B1 (white release lever) 8GB 2Rx4 PC3L 10600R

B5 Memory module slot B5 16GB 2Rx4 PC3L 12800R

B2 Memory module slot B2 (white release lever) 8GB 2Rx4 PC3L 10600R

B6 Memory module slot B6 16GB 2Rx4 PC3L 12800R

B3 Memory module slot B3 (white release lever) 8GB 2Rx4 PC3L 10600R

B7 Memory module slot B7

B4 Memory module slot B4 (white release lever) 8GB 2Rx4 PC3L 10600R
B8 Memory module slot B8

 

 

 

 

 

 

I read in the Owners Manual that the highest ranked DIMMS should be installed first. Although the memory is all quad ranked, I decided to place the 16GB DIMMS “First” as follows:

 

 

A1 Memory module slot A1 (white release lever) 16GB 2Rx4 PC3L 12800R

A5 Memory module slot A5 8GB 2Rx4 PC3L 10600R

A2 Memory module slot A2 (white release lever) 16GB 2Rx4 PC3L 12800R

A6 Memory module slot A6 8GB 2Rx4 PC3L 10600R

A3 Memory module slot A3 (white release lever)

A7 Memory module slot A7 8GB 2Rx4 PC3L 10600R

A4 Memory module slot A4 (white release lever)

A8 Memory module slot A8 8GB 2Rx4 PC3L 10600R

B1 Memory module slot B1 (white release lever) 16GB 2Rx4 PC3L 12800R

B5 Memory module slot B5 8GB 2Rx4 PC3L 10600R

B2 Memory module slot B2 (white release lever) 16GB 2Rx4 PC3L 12800R

B6 Memory module slot B6 8GB 2Rx4 PC3L 10600R

B3 Memory module slot B3 (white release lever)

B7 Memory module slot B7 8GB 2Rx4 PC3L 10600R

B4 Memory module slot B4 (white release lever)
B8 Memory module slot B8 8GB 2Rx4 PC3L 10600R

I had no success with this method. My thoughts are that the server may want all 8 slots filled.

Any ideas? My VAR is not giving me any assistance.

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16 Replies

RE: R715 Memory Configuration Not Optimal - After Upgrade

Hello.

Your memory configuration is not optimal because the memory channels are not balanced thus; slots on each channel must have identical memory modules for both processors. For optimal memory, you will have:

A1, A2, B1 &B2 =16 GB

A5, A6, B5, &B6 = 8 GB

The rest of the slots ought to remain empty.This will give you total memory capacity of 96 GB. However, if want more than 96 GB of memory and are looking to use 16 GB DIMMs, consider purchasing 4 additional modules(16 GB) to be populated on the remaining slots in the similar manner.

Robert Alakara

Dell EMC | Enterprise Services

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craziefro
6 Indium

RE: R715 Memory Configuration Not Optimal - After Upgrade

Thanks for the info Robert!  I will try to see if that configuration works.

Where can I find more information about the "Channels" of memory as they relate to my Dell server.  I have more experience with HP (boooo) and find it more difficult to understand the Dell layout.

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craziefro
6 Indium

RE: R715 Memory Configuration Not Optimal - After Upgrade

I tried the memory in the listed solution of :

A1, A2, B1 &B2 =16 GB

A5, A6, B5, &B6 = 8 GB

and still received the "Memory not optimal" error.  Thinking that it could be an issue with 2 different speeds of memory, I tried only installing the 16GB modules as:

A1, A2, B1, B2 and still received the "Memory not optimal" error.

Thanks again.  I greatly appreciate the assistance!

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RE: R715 Memory Configuration Not Optimal - After Upgrade

Mixing memory with different speed means the channels will operate at the fast frequency. Ensure that you set the memory mode to Memory Optimized. Again, for optimal memory configuration, the memory channels must have identical DIMMs hence balanced. You will therefore need additional 4 8GB DIMMs (total of 8 8GB modules) to populate on the rest of the slots i.e A5, A6, A7 &A8 and B5, B6,B7 &B8. Populating  only slots A5 &A6 on CPU 1 and B5 &B6 on CPU 2 creates memory imbalance with channels C&D on CPU 1 and CPU 2. Memory in the channels have to match. See diagrammatic illustration below:

Robert Alakara

Dell EMC | Enterprise Services

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craziefro
6 Indium

RE: R715 Memory Configuration Not Optimal - After Upgrade

Thanks for the info Robert,

I'm a little confused, you stated that A1, A2, B1 &B2 =16 GB & A5, A6, B5, &B6 = 8 GB would provide optimal memory configuration, but when I installed it in this configuration it was not optimal.

Also, it was my understanding that the mixed memory speeds would operate at the slowest common frequency, not the fastest frequency.

With the configuration of  A1, A2, B1 &B2 =16 GB & A5, A6, B5, &B6 = 8 GB the DIMMS would create an imbalance across channels C&D correct?

In your latest post, you stated that memory channels must have identical DIMMS in each channel,  does that mean that Channel A,B,C,D must be populated or can channel A,B be populated only?

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RE: R715 Memory Configuration Not Optimal - After Upgrade

Pardon me, the channels will operate at slower speed when memory with different speeds are mixed. With the configuration of  A1, A2, B1 &B2 =16 GB & A5, A6, B5, &B6 = 8 GB, there won't an imbalance across channels C&D because they are empty. Imbalance occurs when memory on channels C&D does not match memory on A&B. Yes, can populate only A&B channels. Some BIOS versions do not support 16 GB memory modules. What is your current BIOS?

Robert Alakara

Dell EMC | Enterprise Services

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craziefro
6 Indium

RE: R715 Memory Configuration Not Optimal - After Upgrade

Robert,

Thanks for the update.

I am currently on BIOS 1.5.2

I did attempt to only populate A1, A2, B1 &B2 with 16GB DIMM, I still received the "Memory not optimal error"

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RE: R715 Memory Configuration Not Optimal - After Upgrade

The BIOS is way out of date. Apply the following BIOS updates first then followed by respective iDRAC updates.

BIOS    iDRAC

BIOS    iDRAC

BIOS    iDRAC

BIOS

Robert Alakara

Dell EMC | Enterprise Services

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craziefro
6 Indium

RE: R715 Memory Configuration Not Optimal - After Upgrade

Thanks for the info Robert.  Do you know if I can accomplish the same updates by using the Dell  Deployment Toolkit CD?

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