Koherence Goes Grey: Minimizing Power Consumption

While Koherence’s official color is a burnt orange and (as those who know me well know) I’m partial to black, Koherence went grey this week. Power-wise anyway.

This is a hot week in the Bay Area. CalISO, the California Independent System Operator,  has called flex alerts, and PG&E has called two SmartRate days. To do its part, Koherence (and the entire residence of which Koherence HQ is a part) went on a power reduction spree. I’d already moved “mission critical” items such as key servers and mail hosting to cloud providers, so arguably what remains is somewhat discretionary.

Koherence HQ’s power usage has long been tracked via several WattsUp watt meters. The primary 24/7 power consumer is the network rack, which includes a 24-port Netgear switch, Apple AirPort Extreme, D-Link DIR-605L router, four TiVos, various RF distribution amplifiers, and a VMWare ESXi server. The rack normally runs at around 140 watts.

Grey Mode

As one might guess, most of this infrastructure supports the TiVos and Koherence’s intranet. TV is sacred, so the TiVos need to stay on, along with the RF amplifiers that support them. However they don’t need network connectivity. In fact the entire Koherence intranet could be shut down if I’m not using the local servers. And as for the ESXi server, while the VMs it hosts get a daily workout, it could be shut down for the day and spun back up in the evening after the flex alerts expire.

So what is Koherence drawing in grey mode?

When all is said and done, the rack’s power consumption dropped from 140 watts to about 90 watts.

The power draw difference between the 605L and the AirPort was surprising. The watt meter barely budged when then 605L was disconnected. It consumes something between one and two watts. (Since the 605L is the main router for the residence, it needs to be on all the time. The AirPort is the gateway for the Koherence intranet so got shut off.) In contrast the AirPort drew in the range of 10 watts! Now for a number of reasons I’m not about to trust the intranet to a D-Link router. But I’ll probably look at a more power efficient one in the next upgrade to 802.11ac.

Another surprise was the 24-port Netgear switch. I had a previous model 24-port Netgear that had fans and got quite warm. It was also notorious for crashing. The one I have now is fanless and has been a rather solid performer. But at ten watts with 12 active ports it’s still drawing a bit more than expected. The unmanaged TP-Link 16-port switch has gotten some mentions as a rather efficient switch  and may replace the Netgear since I really don’t need a smart switch here these days.