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I'm thinking of getting a Pi to use as a file and webserver for personal apps and data backup. I heard the Pi consume little power even when running 24/7.

If I attach a laptop HDD to the Pi for data backups, would it increase notable power consumption? Most of the tasks can be done on the SD card, the hard drive is only used twice a month for data backup and occasionally for file access.

When there's no reading/writing activity to the drive, does it consume notable power or is it better to use a huge SD card instead?

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  • Yes, around 200mA: raspberrypi.stackexchange.com/questions/100353/….
    – tlfong01
    Mar 24 '20 at 8:04
  • I suggest configuring the HDD with a sleep time of something like 10 minutes; it'll take several seconds on first access to wake it up, but it's a good compromise if you know that your usage patterns are very occasional like this. This thread has some generally useful information on that and on SMART tests, which you should run periodically to monitor the health of your drive. Mar 24 '20 at 16:10
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    Typically folks try to use at least 2 mirrored drives in backups, such that if one fails, backups aren't lost. Also you may want to buy a disk drive designed for use as a backup device.
    – Nat
    Mar 24 '20 at 21:50
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Interestingly the power consumption of modern HDD is pretty low and comparable with an Rpi.

https://www.pidramble.com/wiki/benchmarks/power-consumption suggests Rpi 3B is around 2W.

https://www.quora.com/Do-SSDs-use-more-or-less-power-than-HDDs-and-by-how-much suggests WD Blue 500G is around 1.4W when active, idle 55mW, sleep .13mW

So power consumption is comparable between an idle Rpi ~2W and an active HDD ~1.5W; and active Rpi power consumption ~5W is much higher than an active HDD at ~1.5W. Idle HDD power consumption is way lower than an Rpi.

For a typical Rpi PSU rated at 5.1V 2.5A there is plenty of overhead for the Rpi and an attached HDD.

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  • Thanks, my question is whether it's economical and also environmental friendly to run a Pi with HDD 24/7 as a personal server. Seems it's not a bad idea. Mar 24 '20 at 9:49
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    Certainly the added impact of the HDD is minimal compared to the Rpi. As for the Rpi itself at 5W it's using 20x less power than a refrigerator. So barely visible in environmental terms.
    – mhaselup
    Mar 24 '20 at 10:02
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Yes, even if they are not spinning, they consume power to keep the drive mounted and be able to communicate with the HDD. This schould be not an issue. In the domain of SBCs the more important thing is that each time they have to spin up the HDD for access, they consume a high peak current. USB 3.0 spec allows for up to 900mA. Depending on your power supply, this may or may not cause some stability issues with your system.

You could consider using an USB Thumb Drive. Those are not as great for high data traffic as HDDs but are not going to introduce instabilities.

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