Memory configuration in PowerEdge T410

Question

Hi, I just bought a brand new Dell PowerEdge T410 with 16GB of RAM (4x4GB units) and 2 processors. After the purchase I decided to install 16GB (2 x 8GB) additional RAM, because I have it in my warehouse and it was sitting there unused... The RAM is exactly the same type (except for brand), so perfectly compatible. If you have a look at this page   you can see the possible memory configuration for the server. There are 4 slots (per processor) and 3 channels. Slots 1 and 4 make the first channel and slots 2 and 3 make the second and third channels (according to the manual). In my case all I could do was to set up 2 channels, therefore I put, for each processor: 1 unit of 4GB in slot 1 (channel 0) 1 unit of 4GB in slot 4 (channel 0) 1 unit of 8GB in slot 2 (channel 1) The system boots up coorectly but it complains with a (non-blocking) message like this:  The memory configuration is not optimal. The recommended memory configuration is [...] and it basically tells me to put one unit of RAM per channel (so 1 unit per slot 1, 2, 3). The problem is that if I do as it suggests, the system gives an error and it tells me that the different channels must have the same size: you cannot have three channels with different sizes: 4GB, 4GB, 8GB. My question is... can I safely ignore this warning/advice?(the server works well). My guess is that the system is compaining because it detects 3 units of RAM but only 2 channels are being used, thus it suggests to exploit all three channels to have optimal performances. Thanks in advance for the help! Giordano

theflash1932 · Answer

If it is going to complain either way, you are better off running like this:

8GB - slot 1

4GB - slot 2

4GB - slot 3

Sure the memory amount is not identical, but it should at least be able to use 3-channel interleaving with 4GB from each channel.

The recommended configuration for 64GB of RAM is 8GB in each slot, so, yes, 16GB on channel 0.

The manual says the following, but it is not clear from the manual exactly how to make that happen ... hard to see how both can be done.

Except for memory channels that are unused, all populated memory channels must have identical configurations.
Memory modules of different sizes can be mixed in A1-A4 or B1-B4 (for example, 2-GB and 4-GB), but all populated channels must have identical configurations.

Dev Mgr · Answer

I wouldn't recommend doing this.

I'd suggest for both processors:

Slot 1: 8GB dimm

Slot 4: 4GB dimm

And nothing else (you'll have 2 unused 4GB dimms).

Typically with this Intel chipset and these Xeon processors, the rule is that each memory channel should be identically configured/populated, unless the channel is unused. 2 x 4GB dimms does not equal 1 8GB dimm in this regard.

giordano.battil · Answer

I see, therefore I will end up with 24GB of RAM.

But what are the risks of running the system with the current configuration I have? Do the RAM work at slower speed? Is there additional overhead?

And one thing is not clear to me: if all channels must be the same size, why then do they claim you can use up to 64GB of RAM? In that case you would be using (per processor)

- 16GB for channel 0

- 8GB for channel 1

- 8GB for channel 2

Isn't this a similar configuration to mine?

Thanks a lot for the help :)

Giordano

giordano.battil · Answer

ok, good observation.

However with the configuration you proposed, the system signals a "stronger" error, saying that the configuration is wrong.

In the configuration I chose instead the message is more a "warning", thus I'll go with this one. I don't want to risk big troubles :)

Thanks again

theflash1932 · Answer

Yes, but knowing that it would, all I'm saying is that if you are going to get an error either way, you'll get better performance at least from that configuration.

giordano.battil · Answer

I tried Dev Mgr's suggestion to use only 24GB in channel 0... got the same warning ^^

I think I'm correct, the systems detects 2 units of RAM not being used in separate channels and signals that as suboptimal condition.

theflash1932, your suggestion produced errors, basically the same ones I was experiencing when not setting up same size channels... ;)

I'll procede with my original solution, if any errors will arise I will report it here.

thanks to you all for the support!

Giordano

PowerEdge Hardware General

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