> Server PS maximum input wattage is 900W. Present draw of 2.0A @ 208V is ~420W, so 420/900 = 46.67%
But in the real world an R640 would *never* draw 900W. Even if you were to load it up with the maximal CPU configuration (2 x 125W TDP CPU per socket), a full load of 2.5" 15K spinning drives, maximum RAM, and three high wattage low-profile PCI-E cards, while simultaneously running CPU, RAM and disk stress tests, you might get in the neighborhood of 550-600W under load. Much the same way that a desktop PC equipped with a nominally "850W" rated active PFC 80+ gold power supply might be powering a motherboard and CPU combo with a high CPU TDP, but total power consumption under stress tests/benchmarks would be nowhere near 850W. That rating exists to ensure that the power supply isn't running anywhere near its max capacity... On Fri, Mar 5, 2021 at 3:33 PM Brian Knight <m...@knight-networks.com> wrote: > On 2021-03-05 15:40, Eric Kuhnke wrote: > > > For comparison purposes, I'm curious about the difference in wattage > > results between: > > > > a) Your R640 at 420W running DPDK > > > > b) The same R640 hardware temporarily booted from a Ubuntu server live > > USB, in which some common CPU stress and memory disk/IO benchmarks are > > being run to intentionally load the system to 100% to characterize its > > absolute maximum AC load wattage. > > We've got a few more hosts waiting to be deployed that are configured > almost identically. I'll see what we can do. > > I'm guessing those tests would pull slightly more power than the vEdge > hosts, just because there's not much disk IO that happens on a > networking VM. These hosts have four SSDs for local storage. > > > What's the delta between the 420W and absolute maximum load the server > > is capable of pulling on the 208VAC side? > > > > https://manpages.ubuntu.com/manpages/artful/man1/stress-ng.1.html > > Server PS maximum input wattage is 900W. Present draw of 2.0A @ 208V is > ~420W, so 420/900 = 46.67% > > > One possible factor is whether ESXI is configured to pass the pci-e > > devices directly through to the guest VM, or if there is any > > abstraction in between. For non-ESXI stuff, in the world of Xen or KVM > > there's many different ways that a guest domU can access a dom0's > > network devices, some of which can have impact on overall steady-state > > wattage consumed by the system. > > The 420W server has its interfaces routed through the ESXI kernel. > We're moving quickly to SR-IOV on new servers. > > > If the greatest possible efficiency is desired for a number of 1U > > things, one thing to look at would be something similar to the open > > compute platform single centralized AC to DC power units, and servers > > that don't each have their own discrete 110-240VAC single or dual power > > supplies. In terms of cubic meters of air moved per hour vs wattage, > > the fans found in 1U servers are really quite inefficient. As a > > randomly chosen example of 12VDC 40mm (1U server height) fan: > > > > https://www.shoppui.com/documents/9HV0412P3K001.pdf > > > > If you have a single 12.0VDC fan that's a maximum load of 1.52A, that's > > a possible load of up to 18.24W for just *one* 40mm height fan. And > > your typical high speed dual socket 1U server may have up to eight or > > ten of those, in the typical front to back wind tunnel configuration. > > Normally fans won't be running at full speed, so each one won't be a > > 18W load, but more like 10-12W per fan is totally normal. Plus two at > > least two more fans in both hot swap power supplies. Under heavy load I > > would not be surprised at all to say that 80W to 90W of your R640's > > total 420W load is ventilation. > > Which is of course dependent on the environmentals. Fan speeds on our > two servers are 25% for the 260W vs. 29% for 420W, so not much > difference. Inlet temp on both is ~17C. > > I checked out another R640 heavily loaded with vEdge VMs, and it's > pulling similar power, 415W, but the fan speed is at 45%, because inlet > temp is 22C. > > The TDP for the Xeon 6152 is 140W, which seems middle-of-the-road. From > the quick survey I did of Dell's configurator, the R640 can take CPUs up > to 205W. So we have headroom in terms of cooling. > > > In a situation where you're running out of power before you run out of > > rack space, look at some 1.5U and 2U high chassist that use 60mm height > > fans, which are much more efficient in ratio of air moved per time > > period vs watts. > > Or ask the colo to turn the A/C lower ;) (that moves the power problem > elsewhere, I know) > > Thanks, > > -Brian >
