While pulling together a build document for an ESX upgrade project I came upon an interesting challenge regarding DIMM placement and also established a few good resources worthy of future reference.
Anyway, back to my build. Equipment previously spec’d by a predecessor arrived on my desk. 14 x HP Proliant DL380G6 Dual CPU with 60gb RAM, I won’t elaborate on other hardware aspects as that’s not the point of this item. And yes, I have a big desk.
The 60gb comprised of 6 x 2gb and 12 x 4gb DDR3 Dual Rank DIMMs.
The 3rd party supplier built server arrived with the RAM positioned:
3rd Party shipped
There is no doubt as to whether the server would work but I was keen to understand the optimum performance achievable by following manufacturer recommendations.
The DL380G6 uses the Xeon 5500 architecture and has 3 memory channels per CPU, channel 1 being ‘closest’ to the processor.
The HP documentation suggests the population order should follow the alphabetical notation and not the slot number. To further confuse matters the order of population starts from the white DIMM slot.
For those of you not having seen inside the server the white DIMM slots are numbered 3, 6 and 9.
This equates to :
Channel 1 using slots 3 + 6 + 9
Channel 2 using slots 2 + 5 + 8
Channel 3 using slots 1 + 4 + 7
HP DL380G6 System Board
Which, in memory channel terms looks like this…
RAM, CPU and Memory Channel Explanation
HP state that memory should be balanced across memory channels and CPUs, the original build only met one of the criteria for an optimal build.
Here’s the finished placement following HP guidelines.
HP correct placement
Resources reviewed to assist with my conclusions
This image was taken from page 17 of the HP Proliant DL380 G6 Server User Guide, the document is located here:
http://bizsupport1.austin.hp.com/bc/docs/support/SupportManual/c01705681/c01705681.pdf
Populating the 18 slots has been taken from HP the recommendation in Table 6 Page 10 of this document:
ftp://ftp.hp.com/pub/c-products/servers/options/Memory-Config-Recommendations-for-Intel-Xeon-5500-Series-Servers-Rev1.pdf
HP DDR3 Memory configuration tool:
http://h18004.www1.hp.com/products/servers/options/tool/hp_memtool.html
