8 X 8GB or 4 X 16GB for energy efficiency

[adnan]

Hello

Can any experts comment on this. Installing 64GB RAM into a machine, will 4 X 16GB use less energy then 8 X 8GB and if so, is there much difference.

 

[BlueFox]

Generally fewer DIMMs results in lower energy usage. A difference of 4 DIMMs is not significant however.

 

[niekbergboer]

Larger DIMMS are generally a bit more expensive per Gigabyte than their smaller counterparts. The question is how that compares to the electricity cost saved over the expected time that you'll use the server.

Where I live, and assuming a 4-year lifetime, the break-even point is some $8/Watt (purchase price difference per 24/7 Watt of per difference).

Sadly, it's generally not worth it going for low-power parts.

 

[BLinux]

using fewer DIMMs will usually save *some* energy. in DDR2 days, I measured quite the difference. also, going with lower voltage memory will also save a few watts here and there. the other thing i discovered recently is that at least with the DDR3 I was testing, at idle when there isn't much RAM activity, installing 2x DIMMs vs 16x DIMMs made 0 watt difference at idle - i didn't test further, but i expect there to be a difference if i ran a RAM benchmark. so, if your system is sitting idle a lot, it might not matter at all and not worth the investment.

any power savings in this area is minimal though. if your goal is to squeeze every bit of lower wattage and you've already addressed everything else, then go for it. i found 16GB PC3L for pretty cheap ($30-35 ea.) so I went with 16GB DIMMs anyway.

 

[BlueLineSwinger]

Regardless of possible energy consumption concerns, assuming it's economically viable, I'd rather go with fewer, larger DIMMs in order to make make possible expansion later simpler and cheaper.

 

[Evan]

All depends what the dimms are as well. For example I see some new generation ddr4 rdimm in 16gb that's now single rank and the new smaller process node, I am sure they would use less than the older larger process that's 2R and more packages.