[57north-discuss] Dell Servers - Calculations etc

[Calum Enterobsidian]

On 11 Apr 2014, at 10:04, "Tony Travis" <tony.travis at minke-informatics.co.uk> wrote:
> Hi, Calum.
> 
> I've no experience of the Dell systems, but modern PSU's are designed to
> be 80% efficient (i.e. 20% of the electricity consumed by the PSU is
> dissipated as heat). Most servers use PSU's that are ~50% over-capacity
> because of high start-up currents. In addition, typical CPU heat
> spreaders are rated at ~100W per socket maximum. This sets an upper
> limit to power consumption regardless of how many cores are in the
> processor. In practice I observe ~250-350W power consumption (according
> to CPU activity) by each of my two dual 2-core (Opteron 2212) processor
> servers running with 32GiB RAM and 16 at 500GB disks in each although the
> PSU's are rated at 700W. The 2U Opteron 200 systems I donated to the
> "Space" draw about 150W each. I think you're right to be concerned, but
> I think that your power calculations are a bit on the pessimistic side.
> 
> Bye,
> 
>  Tony.
> 

Hi Tony,

Without knowing what each server actually draws, max load was the only thing I had to go on when I did these quickly at 1 in the morning. They assume that the server is in its worst possible loading condition, so it's taking the full power available from the output - max stall load. 

I think the main constraints we are going to have are the wiring in the building and the loading capacity of the floor. Without looking at both I can't give an accurate figure accurate figure beyond 8, as the MSL may exceed the wiring specification. It loos like the building may the biggest factor in the selection.

Regards
Calum