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Dell PowerEdge T710 Memory Upgrade

Posted on 2012-08-14
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Dell PowerEdge T710
I am having a heck of a time trying to understand this memory configuration Dell is saying I have to do on the server.

This server has 2 processors and 18 memory slots (9 per processor) they are configured as such:
A1 | A4 | A7 | A2 | A5 | A8 | A3 | A6 | A9
B1 | B4 | B7 | B2 | B5 | B8 | B3 | B6 | B9

In there right now is 12 GB of memory, 6x2GB sticks of RDIMM Dual Rank PC3 10600 (1333).

We wanted to upgrade to 48GB of memory, 6x8GB sticks of RDIMM, but did not read up or see the single, dual, quad rank system.

Our purchasing department bought 6x8GB sticks of RDIMM Quad rank sticks.

I am being told by a Dell technician "In a nutshell, you cannot put in more than 2 sticks of quad rank memory with any given processor per server.  (I.E., if you have 2 processors, you can use a total of 4 quad rank memory sticks.)"

The link he gave me to the Technical Guide for the T710 has a chart that says (and other sources say the same thing) -
"DIMM Configurations: Quad Rank RDIMM - 2 per channel per processor (12 Total)"
"Simply put, no more than 12 quad-rank DIMMs can be installed in these servers"

So what exactly are they considering a "Channel" and why does the table and websites I have read say 2 per channel (12 Total) and the Dell guy says only 2 per processor.

So far I have guestimated that:
A1 | A2 | A3 | B1 | B2 | B3 is one channel (Making it 3 channels altogether)
or
A1 | A2 | A3 and B1 | B2 | B3 are two separate channels (Making it 6 Channels altogether)

That is just the beginning of my questions so far and wanting to see if anyone can put it into a form that is understandable and not contradicting.

Then the configuration comes into play and that gets complicated as well. Please let me know if my question even made sense.
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Question by:WalkerCountyTX
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andyalder earned 2000 total points
ID: 38293911
Generically Xeon 55/5600 series CPUs have a 3 channel memory controller built into the CPU, so a one processor DellT 710 has 3 memory channels and a two CPU one has 6 channels.

You cannot have more than 8 ranks per channel so 2 quad rank DIMMs fills a channel so you can have 6 of them on a single CPU server and 12 of them on a 2CPU server.

Whoever bought quad rank DIMMs was very silly, dual rank 8GB DIMMS are the sweet-spot for price.

You can just about get away with any match of RDIMMs so long as you don't break the 8 rank rule whatever Dell tell you.

I do not know Dell's numbering but the physical layout would be something like the following (assuming 2 CPUs). All manufacturers lay out the RAM similarly although numberings vary.

82-82-82-CPUCPU-28-28-28

Assuming 1 CPU the 2GB ones will have to come out.
88-88-88-CPU
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by:andyalder
ID: 38293985
This will help - note that Dell's reference to balanced is incorrect according to Intel. What they refer to as balanced isn't even "near balanced" it's NUMA node balanced but never mind, it's only semantics.

http://www.dell.com/downloads/global/products/pedge/en/server-pedge-installing-upgrading-memory-11g.pdf

There's an old version of that doc that has some ridiculous rules floating about that you may have seen, says all channels have to be populated the same. I'll try to dig it up again tomorrow just for a laugh, don't worry though, it's wrong.
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by:andyalder
ID: 38293999
Scratch that - it *is* the old doc. "All populated channels must have the same DIMM arrangement." is total nonsense. Rest of the doc is OK though.
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Author Comment

by:WalkerCountyTX
ID: 38300462
Thank you for the reply, and I will be putting the memory in today.

I do not think anyone was thinking about ranking when they purchased the memory. But I have let it be known that buying dual rank from this point forward is the way to go. We have another server (same layout) that we want to upgrade so it will be bought soon. :)

Once again thank you for the information, the more I learn the happier I am...Dell is just frustrating.
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by:andyalder
ID: 38300540
You can save a bit on the second server, you're taking 6*2GB dual rank (2R) out of this one and probably have 6*2GB in that too, so for 48GB you an buy 6*4GB 2Rx4 and use the RAM you already have.  On Dell's UK site the 8GB 2Rx4 are £104 and the 4GB 2Rx4 are £56.
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Author Comment

by:WalkerCountyTX
ID: 38300572
To shed some light on the subject in our case also:

The layout is thus.

A1|A4|A7|A2|A5|A8|A3|A6|A9 CPU1 - CPU2 B9|B6|B3|B8|B5|B2|B7|B4|B1

That same quick reference guide you just gave is the one I found yesterday that says that the channels are set as such.

A1|A4|A7 and B1|B4|B7 are channel 1
A2|A5|A8 and B2|B5|B8 are channel 2
A3|A6|A9 and B3|B6|B9 are channel 3

What i am getting out of it and plan to test is:
You can have 2 Quad rank DIMMs per channel
there are 3 total channels
that means I can out a stick in AB1|AB2|AB3 and it will work.
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Expert Comment

by:andyalder
ID: 38300589
Yes, they're the right slots, you could leave the current 2GB ones in too if you wanted more than 48GB (You'd move them to AB4, AB5 and AB6).
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Author Closing Comment

by:WalkerCountyTX
ID: 38300591
Thank you for the time you have taken to get back with me.
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