147 lines
7.2 KiB
Markdown
147 lines
7.2 KiB
Markdown
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---
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title: "Power consumption and failures prevention"
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date: 2020-08-14T18:00:00+02:00
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---
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Providing a full storage service means having computers up 24x7. On one hand, if we power off the local storage server
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when we aren't using it, we'll have to find a solution to respect the backup policy and synchronize with remote servers
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that could be down at the moment. On the other hand, if we let the storage server up all the time, it will consume
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unnecessary resources and throw money down the drain. I deeply know that a personal computer, which is idle most of the
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time, doesn't consume so much power. This is my conviction. But how to verify it?
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With [observability]({{< ref "posts/increased-observability-with-the-tig-stack" >}}), I thought it would be easy to
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gather power consumption via built-in sensors. I tried something that I know,
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[lm_sensors](https://hwmon.wiki.kernel.org/lm_sensors), which is included in the Linux kernel and exposes CPU
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temperatures, fans speed, power voltages, etc.
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```
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storage2 ~ # sensors
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k8temp-pci-00c3
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Adapter: PCI adapter
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Core0 Temp: +30.0°C
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Core0 Temp: +22.0°C
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Core1 Temp: +30.0°C
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Core1 Temp: +16.0°C
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acpitz-acpi-0
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Adapter: ACPI interface
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temp1: +40.0°C (crit = +75.0°C)
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atk0110-acpi-0
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Adapter: ACPI interface
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Vcore Voltage: +1.10 V (min = +1.45 V, max = +1.75 V)
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+3.3 Voltage: +3.39 V (min = +3.00 V, max = +3.60 V)
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+5.0 Voltage: +4.97 V (min = +4.50 V, max = +5.50 V)
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+12.0 Voltage: +12.22 V (min = +11.20 V, max = +13.20 V)
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CPU FAN Speed: 3391 RPM (min = 0 RPM, max = 1800 RPM)
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CHASSIS FAN Speed: 0 RPM (min = 0 RPM, max = 1800 RPM)
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POWER FAN Speed: 1662 RPM (min = 0 RPM, max = 1800 RPM)
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CPU Temperature: +26.0°C (high = +90.0°C, crit = +125.0°C)
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MB Temperature: +37.0°C (high = +70.0°C, crit = +125.0°C)
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```
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The ACPI interface returns some voltages measurements. But I doubt they can be used to find the instant consumption in
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watt (W) and extrapolate the consumption over time in kilowatt-hour (kWh). On laptops, such information can be computed
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from battery statistics. Unfortunately, all computers of the infrastructure are desktops without batteries.
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I needed to buy a product. A [lot](https://modernsurvivalblog.com/alternative-energy/kill-a-watt-meter/)
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[of](https://www.howtogeek.com/107854/the-how-to-geek-guide-to-measuring-your-energy-use/)
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[websites](https://www.pcmag.com/news/how-to-measure-home-power-usage)
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[talk](https://michaelbluejay.com/electricity/measure.html) about how to measure power consumption for computers and
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even for the whole house. The common thing that comes out is the recommendation to use a
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[wattmeter](https://en.wikipedia.org/wiki/Wattmeter).
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{{< rawhtml >}}
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<p style="text-align: center;"><img src="/zaeel-wattmetre.jpg" alt="Wattmeter" style="width: 25%;"></p>
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{{< /rawhtml >}}
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It's an instrument which can be plugged between the power outlet and your device to measure how much energy is consumed
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instantaneously (W), over time (kWh) and even the total price if you have configured the kWh price. There is a LCD to
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display the results. A wattmeter is cheap. I've bought [this
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model](https://www.amazon.fr/dp/B07GN5NPDJ/ref=cm_sw_r_tw_dp_x_FMMiFb2911HN7) which does a good job. Sadly, we cannot
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gather the data from the LCD to load them to the metrics infrastructure easily. It also lacks of precision for the
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price. We can enter only two digits after the floating point while the energy provider gives us a price with five
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digits.
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Speaking of the price, my [energy provider](https://www.engie.be/fr/) publishes a beautiful but beyond understanding
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[grid of prices](https://www.engie.be/fr/energie/electricite-gaz/prix-conditions). They are dependent on the pack of
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products, the region and the distributor. They change over time. You can have an electrical counter for the day and for
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the night. Moreover, price is displayed in cents and not euros! I called them to have a price estimation. Come on, we
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are in a digitized world. They should, at least, display the current price of the contract somewhere in the customer
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panel.
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During my researches, I found that we could use an uninterruptible power supply (UPS) to gather power consumption
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metrics. As a bonus, it is able to protect from power variations and interruptions that could harm computers. However,
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they are quite expensive. Their prices range from 50€ to hundreds of euros. As I'm a total newbie in this domain, I've
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read this detailed [guide](https://www.materiel.net/guide-achat/g13-les-onduleurs-et-prises-parafoudre/1/) (FR) to gain
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some knowledge. So I decided to buy an [APC Back-UPS Pro
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550](https://www.apc.com/shop/be/en/products/APC-Power-Saving-Back-UPS-Pro-550/P-BR550GI).
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{{< rawhtml >}}
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<p style="text-align: center;"><img src="/apc-back-ups-pro-550.jpg" alt="UPS" style="width: 25%;"></p>
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{{< /rawhtml >}}
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It has an USB interface to control it with [apcupsd](https://en.wikipedia.org/wiki/Apcupsd) and display power
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information with the "apcaccess" binary. It's compatible with both Debian and FreeBSD and it even has a [telegraf
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plugin](https://github.com/influxdata/telegraf/tree/master/plugins/inputs/apcupsd)!
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```
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storage1 ~ # /usr/local/sbin/apcaccess
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APC : 001,036,0867
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DATE : 2020-07-30 15:56:46 +0200
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HOSTNAME : storage1
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VERSION : 3.14.14 (31 May 2016) freebsd
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UPSNAME : storage1
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CABLE : USB Cable
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DRIVER : USB UPS Driver
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UPSMODE : Stand Alone
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STARTTIME: 2020-07-26 18:28:21 +0200
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MODEL : Back-UPS RS 550G
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STATUS : ONLINE
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LINEV : 234.0 Volts
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LOADPCT : 10.0 Percent
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BCHARGE : 100.0 Percent
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TIMELEFT : 37.5 Minutes
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MBATTCHG : 5 Percent
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MINTIMEL : 3 Minutes
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MAXTIME : 0 Seconds
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SENSE : Medium
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LOTRANS : 176.0 Volts
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HITRANS : 282.0 Volts
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ALARMDEL : No alarm
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BATTV : 13.7 Volts
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LASTXFER : No transfers since turnon
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NUMXFERS : 0
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TONBATT : 0 Seconds
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CUMONBATT: 0 Seconds
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XOFFBATT : N/A
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SELFTEST : NO
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STATFLAG : 0x05000008
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SERIALNO : 4B1939P01928
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BATTDATE : 2019-09-23
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NOMINV : 230 Volts
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NOMBATTV : 12.0 Volts
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NOMPOWER : 330 Watts
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FIRMWARE : 857.L7 .I USB FW:L7
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END APC : 2020-07-30 15:57:32 +0200
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```
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The 550 is the first model of the Back-UPS Pro range so it has [IEC C13 power
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plugs](https://en.wikipedia.org/wiki/IEC_60320#C13/C14_coupler) only, suitable for computers, but no [Euro/French
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plugs](https://en.wikipedia.org/wiki/AC_power_plugs_and_sockets#CEE_7.2F5_socket_and_CEE_7.2F6_plug_.28French.3B_Type_E.29)
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compatible with any electrical device. As I connect only a single computer to the UPS, this is the most economical
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solution.
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Once the data had been fed to the observability platform, I was able to import this [beautiful
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dashboard](https://grafana.com/grafana/dashboards/10835) from the Grafana community. I've customized it to my own needs
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and here is the result:
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[](/power-consumption-storage1.png)
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[](/power-consumption-storage2.png)
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[](/power-consumption-storage3.png)
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You can download my dashboard [here](/grafana-power-consumption.json).
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Our winner is *storage3* which costs less than a kebab per year! The worst case is *storage2*, the old hardware, that
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consumes the equivalent of an incandescent light bulb. See, the power consumption is not so bad after all.
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