Distributing DIMMs in N4000 server.

[Fedon Kadifeli]

We had an N4000 server with 4 GB memory (1 carrier, 8x512MB DIMMs). After we added 4 GB memory (2 carriers, 8x256MB DIMMs each) more to this server, we started getting the following message:

WARNING: Current loading of DIMMs failed the distribution check. This
means the memory subsystem may not operate at optimal
performance levels. To correct, refer to DIMM loading rules
and re-distribute DIMMs.

The current distribution is like this:

--------------------------------------------
0a 2a 1a 3a 3b 1b 2b 0b
--- ---- ---- ---- ---- ---- ---- ----
EXT 0 512 512 512 512 512 512 512 512
EXT 1 256 256 256 256 256 256 256 256
EXT 2 256 256 256 256 256 256 256 256
--------------------------------------------
System Total (MB): 8192


Which is the best distribution with the hardware at hand?

Is this reasonable for example?

--------------------------------------------
0a 2a 1a 3a 3b 1b 2b 0b
--- ---- ---- ---- ---- ---- ---- ----
EXT 0 512 512 256 256 256 256 512 512
EXT 1 512 256 256 256 256 256 256 512
EXT 2 512 256 256 256 256 256 256 512
--------------------------------------------

Any opinions?

[Torsten.]

You are "almost" right, but pay attention to the slot sequence 0-2-1-3-3-1-2-0 !!!

Follow this hint:

For best performance, install DIMMs evenly among the carriers, loading carriers 0, 1, 2, and 3 in sequence. For example, four 512MB memory DIMM pairs should be loaded into slot 0a/b on carrier 0, then slot 0a/b on carrier 1, and so on.

[Fedon Kadifeli]

So, you mean the "correct answer" is?

-------------------------------------
..... _0a _2a _1a _3a _3b _1b _2b _0b
..... --- --- --- --- --- --- --- ---
EXT 0 512 256 512 256 256 512 256 512
EXT 1 512 256 256 256 256 256 256 512
EXT 2 512 256 256 256 256 256 256 512
-------------------------------------

[Mohanasundaram_1 · Accepted solution]

Hi Fedon,

The reply before this was correct. I keep it simple.

I take the highest capacity memory DIMMS and start installing them equally on all the available memory carriers starting from 0a and progressing to 0b,1a,1b.... and so on.

Then take the next highest capacity memory DIMMs and repeat the same. Continue this step until you are done with the DIMMs.

It does not require a big algorithm, just follow the simple rule. The N4000 memory loading rules document talks about this thoroughly.

With regards,
Mohan.

[Brad Baron]

The loading rules should be listed on the inside top cover of the N4000.

[Ted Buis]

The loading rules should also be able to be found from the hardware manuals via www.docs.hp.com. However my advice is to get a fourth memory carrier. Memory carriers add bandwidth to the memory system, at about 2.1GB/sec per carrier in the N-class. It is hard to spread your memory evenly accross three carriers.