DL380G6 Memory Config Rules

[Toyo_1]

Been through the Mem Config tool and are trying to understand why a 491332-371 base server (1 CPU, 3 x 2Gb modules) when upgraded to 2 CPUs with 16Gb total (i.e. original 3 x 2Gb modules plus 2 x 4Gb (500658-B21) plus 1 x 2Gb (500656-B21)) ends up with 10Gb on one CPU and 6Gb on the other.
i.e. config tool has CPU 2 Ch1 2Gb + 2Gb, Ch2 4Gb + 2Gb and CPU 1 Ch1 2Gb, Ch2 4Gb.


Why have 2 modules on Ch1 and Ch 2 for CPU 2 and not 1 module per channel for both CPUs? i.e. CPU 1 & CPU 2 - Ch1 2Gb, Ch2 2Gb, Ch3 4Gb

[asqwq]

hi
you can read user guide for dl380 g6 on this address:
http://www13.itrc.hp.com/service/cki/docDisplay.do?docLocale=en&docId=emr_na-c01705681-2

[Toyo_1]

If I read the user guide correctly then the above config is recommended because it allows the memory to operate in either Mirrored or Lockstep mode (both of which don't allow Ch3 to be populated).
If however I don't necessarily want to utilise either of those modes then am I correct is assuming that I could actually populate then memory as CPU 1 & CPU 2 - Ch1 2Gb, Ch2 2Gb, Ch3 4Gb - albeit leaving the server with reduced memory redundancy.

[Dhanesh Amirthalingam]

Memory configuration and population rules and logic..
â ¢ There are many rules governing how DDR3 memory should be installed in a server.
â ¢ Factors that determine how DIMMs may be installed include:
â ¢ DIMM type, DIMM rank, clock speed, position to the processor (closest/furthest), number of memory channels, and desired redundancy features.
DDR3 Memory comes in two types; RDIMM and UDIMM.

RDIMM or Registered - Maximum server capacity up to 144GB
â ¢ Larger capacities and include address parity protection & advanced memory protection.
â ¢ Less electrical load on the memory controller; allows systems to remain stable with more memory modules.
â ¢ Used for applications requiring scalability and stability.
UDIMM or Unbuffered - Maximum server capacity up to 24GB.
â ¢ Lower power consumption, limited in capacity but lower in price.
â ¢ Uses SDRAM chips directly connected to memory controller without a buffer.

http://h18004.www1.hp.com/products/servers/options/tool/hp_memtool.html



I think it ill help you out lot⠦⠦.

[Pieter 't Hart]

I think another criterium counts : look at page 45.
when all 3 slots of a channel are used, memory speed is reduced.
Therefore 2 slots each of 3 channels are populated on processor-1. and 2 slots of 2 channels for processor-2.

[Toyo_1]

I understand that. What I'm proposing is to use one slot on each of the three channels on each CPU.
i.e. 6 DIMMs - 1 in each of slot 1 on Ch1, Ch2 & Ch3 on each CPU.

[Pieter 't Hart]

Sorry if i misunderstood.

The user guide confirms your choice would be allowed:
For Advanced ECC mode configurations with multiple processors, populate the DIMM slots for each processor in the following order:
â ¢ RDIMM: Sequentially in alphabetical order (A through I).
=> A-B-C is one module per channel.

There may be a criterium not explained in the manual why the tool prefers to populate two slots per channel or to leave channel-3 preferably unused (for cpu1 and not for cpu2).

There are other posts about the mem config tool suggesting it has (a) bug(s) => better contact HP about this.

[Toyo_1]

No worries Pieter. Thanks for making the effort to respond. Much apreciated.

The config tool suggests -
CPU 1 Ch1 2Gb, Ch2 4Gb
CPU 2 Ch1 2Gb + 2Gb, Ch2 4Gb + 2Gb

The fact that it leaves Ch3 empty on both CPUs suggests to me that the tool prefers mirroring or lockstep which kinda makes sense. Dosn't explain why it didn't suggest the following config (i.e. split the memory equally across CPUs)-
CPU 1 Ch1 2Gb, Ch2 4Gb + 2Gb
CPU 2 Ch1 2Gb, Ch2 4Gb + 2Gb

Will discuss further with suppliers engineers.

[KJ C]

could I configure Box 1
A, B, C (8GB)
D (2GB)
E (2GB)
&
F (4GB)

that would be a total of 64GB

Box 2
A, B, C (2GB)
D (2GB)
E (2GB)
&
F (4GB)

that would be a total of 20GB

Box 3
A, B, C (2GB)
D (4GB)
that would be a total of 20GB

thanks