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Does it require to add memory in a group of 4 chips to HP ProLiant DL380 server ?

Posted on 2016-11-02
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Last Modified: 2016-11-03
I have a HP ProLiant DL380 Gen 9 server with one processor. The processor has 12 memory sockets. Here is the current memory chips and the slot#:
1:   16 GB
2:     8 GB
3
4:    16 GB
5:      8 GB
6
7
8:     8 GB
9:   16 GB
10  
11:   8 GB
12:  16 GB

I've been thinking to add either 4 x 8 GB or 2 x 16 GB. The 2 x 16 GB is preferable but I was told they require in a group of four. Is it true?
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Question by:Castlewood
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7 Comments
 
LVL 21

Assisted Solution

by:CompProbSolv
CompProbSolv earned 250 total points
ID: 41870856
According to the User Guide found at: http://h20565.www2.hpe.com/hpsc/doc/public/display?sp4ts.oid=7271241&docLocale=en_US&docId=emr_na-c04436966
You can use 2 or 3 DIMMs per channel.
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LVL 30

Expert Comment

by:Scott C
ID: 41870925
What does it say on the inside of the cover?  That is where I always get my information for adding memory and making sure the correct slots are populated.

If budget allows, I'd go for a group of 4 of the 16GB just to have the memory available.
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Expert Comment

by:andyalder
ID: 41870927
It's preferable to have equal ammounts of Ram on each channel but it only gives a tiny speed improvement adding 4 small sticks instead of 2 big ones. Intel will show you a whitepaper showing just how much better the STREAM memory benchmark runs if the RAM is spread evenly but real life isn't like the STREAM benchmark. Intel won't show you the SPECint benchmark in their literature as that's more like real life and shows the tiny tiny difference.

Just shove the big sticks in 10 and 7 will work OK.

Actually though you can make it even with a bit of shuffling because 2*8=16

16
16
0
16
16
0
8
8
16
8
8
16

Hey presto 32GB on each channel :)
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LVL 8

Expert Comment

by:Senior IT System Engineer
ID: 41871360
@Castlewood: You can try to use this website to validate your settings: https://h22195.www2.hpe.com/DDR4memoryconfig/Home/LEGAL to ensure compatibility.
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LVL 55

Expert Comment

by:andyalder
ID: 41871881
HPE's memory configurator is all very well for the most simple configurations but this is what it comes out with for this situation if you pick the option that adds 2 16GB sticks:

 Channel 1 : 1 x ( 16GB 2R, 8GB 2R, 0GB )
Channel 2 : 1 x ( 16GB 2R, 8GB 2R, 0GB )
Channel 3 : 1 x ( 8GB 2R, 16GB 2R, 16GB 2R )
Channel 4 : 1 x ( 8GB 2R, 16GB 2R, 16GB 2R )

It's too stupid to shuffle the current RAM so it ends out putting 24GB on one channel and 40GB on another, very unbalanced indeed. My layout is far better and BIOS will validate it during POST.
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Author Comment

by:Castlewood
ID: 41872464
Andy,

My existing 8GB ram is 1R instead of 2R as you listed. Would that matter?
By the way, help me understand the difference between 8GB 1R and 8GB 2R? Would 8GB 2R be more like with double speed or capacity and become 16GB 1R ? I may be silly but need help...
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LVL 55

Accepted Solution

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andyalder earned 250 total points
ID: 41872579
The R stands for "rank", in the old days people called 1R "single sided" and 2R "double sided" even when it didn't relate to the physical chip layout. A 2R DIMM can be thought of as two 1R DIMMs glued together so they fit in a single slot, Maximum bus loading is 8 ranks per channel so if you were to have two 4R DIMMs in one channel the 3rd bank would have to be left empty. Two 8GB 1R DIMMs behave exactly the same as one 16GB 2R DIMM.

What I listed in my 2nd post was just the rubbish HPE's memory configurator came out with, I only listed it to show that their online configurator gave less than optimal solutions.
Just populate with two more 16GB DIMMs (1R or 2R doesn't matter) using the shuffling I provided in my first post.

Channel 1 : 1 x ( 16GB 2R, 8GB 1R, 8GB 1R )   =32GB
Channel 2 : 1 x ( 16GB 2R, 8GB 1R, 8GB 1R )   =32GB
Channel 3 : 1 x ( 16GB 2R, 16GB 2R )                =32GB
Channel 4 : 1 x ( 16GB 2R, 16GB 2R )                =32GB
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