Full Slot RAM

[Farshid_Moradi]

Hi,

Please let me know if I want to use 24 slots of RAM in DL380 G8 while i have 2 processor, does it matter if i use single rank or dual rank modules? 

[derick_souza]

Please check the link below:

http://h18000.www1.hp.com/products/servers/options/tool/hp_memtool.html

http://h18000.www1.hp.com/products/quickspecs/14212_div/14212_div.PDF

HP Memory

NOTE:

HP memory from previous generation servers are not qualified or warranted with

this HP ProLiant Server. HP SmartMemory is required to realize the memory

performance improvements and enhanced functionality listed in this document for

Gen8. For additional information, please see the HP SmartMemory QuickSpecs at:

http://h18000.www1.hp.com/products/quickspecs/14225_div/14225_div.html

NOTE:

LRDIMM, RDIMM, UDIMM, and HDIMMs are all distinct memory technologies and

cannot be mixed within a server. The majority of ProLiant Gen8 servers support

LRDIMM, RDIMM and UDIMMs.

Registered DIMMs (RDIMMs)

[David_Schwartzs]

Using single rank vs. dual rank won't really matter. (Quad-rank is a different story, as there are limitations there, but since you didn't ask about it, I won't go into detail)

Here's what you should know, though:
1) To avoid annoyances with slot population ordering, you should probably try to stick to being consistent - do all single rank or all dual rank. I recommend dual rank because they can be scaled to higher capacities - 16GB vs 8GB. (There are rules regarding populating single rank chips closer to the processor versus dual rank chips.)
2) If you install all 24 slots with 1600 (12800) memory, the memory clock speed goes down to 1333. (versus the full 1600 with 8 or 16 slots filled) However, this may or may not be terribly relevant, which I'll explain in a minute.
3) If you fill all 24 slots with 1333 (10600) memory, the memory clock speed goes down to 1066 (versus the full 1333 with 8 or 16 slots filled). Again, may not be terribly irrelevant, which I'll explain.

In order to even achieve 1600 speed, you have to be using a E5-2643 or higher series processor (with the exception of the E5-2637). In order to use 1333 speed, your processor must be E5-2620 or higher. So depending on the processor you're using, buying the memory with higher speed capability may end up clocking downward anyway regardless of number of slots you fill.

In any case, if you knew nothing else and you didn't want to bother unraveling this mess, I could simply advise you that running 8 or 16 slots filled provides the best performance in most situations regardless of processor or type of RAM installed.

Hope this helps!