I have recently turned by Raspiberry Pi 4B into a small NAS. However, I noticed that the Pi disconnects from Ethernet from time to time. Whenever this happens (e.g. ssh not responding or Pi not reachable in network) the green and yellow lights of the Pi's Ethernet port turn off, while the red front led is still on, which made me think that the 4A charger might not supply the whole system with enough power. My setup looks as follows:

All information I have found regarding this problem (like this post for example) was rather old and even suggested that a 4A power supply should be enough. Sadly, I did not really find any information about how much current the hard drive draws (amazon states that it requires 8W, but I don't really know how reliable that information is). I also do not have the required equipment to measure any of the components' current drain or the quality of the power supply.

Therefore, I wanted to reach out to the community to ask whether you think that the power supply could be the problem here. Also, if this is the case, do you have a suggestion for a suitable Type-C power supply?

Thank you very much in advance!

  • grep "Under-voltage" /var/log/syslog should confirm if that is really the problem. It can't really rule it out if it is a periphery drive that's failing, but then there will be other clues about that, as there should be about the eth port going offline: Note that the amber light should always be on if the cable is plugged in at both ends and both systems have power. It indicates there's a link, which does not necessarily mean "viable connection with an IP address etc.", it just means it is physically connected, so if it is going out something odd may be happening.
    – goldilocks
    Mar 25, 2022 at 16:43
  • @goldilocks grep "Under-voltage" /var/log/syslog yields nothing. What exactly do you mean by "other clues"?
    – Roysten R.
    Mar 25, 2022 at 17:51
  • That's where the kernel, amongst other things, logs errors, and if the ethernet port is going down like that there should be some (albeit cryptic) indication of why. Actually I should qualify that: This depends a bit on how system logging is configured and I have not looked at the default on current RpiOS, but if that file exists and has lots of stuff in it, there are also timestamps, you could look back in it to see if there is anything that looks pertinent. The output from dmesg is another possibility.
    – goldilocks
    Mar 25, 2022 at 20:07

2 Answers 2


Your power supply is not big enough. Look at this link: https://www.seagate.com/www-content/datasheets/pdfs/barracuda-2-5-DS1907-2-1907US-en_US.pdf It shows the R/W current 1.7/1.8 amps. The recommended Pi power supply is 3A minimum. That puts you at 4.8 Amps recommended minimum. I would suggest a power supply of at least 6 Amps preferably more.

  • Thank you, somehow I did not catch that information in the documentation. However, in the pdf it says that the drive requires 1.7/1.8 watts, not ampere. I really do not know a lot about electrical engineering, but with my limited knowledge I would calculate the current drain as 1.7W / 5V = 0.34A. But please correct me if I missed something here.
    – Roysten R.
    Mar 26, 2022 at 1:20
  • You are correct but it also states it needs 1A for startup. A 5A should work fine.
    – Gil
    Mar 26, 2022 at 18:53

No matter how big the power supply the absolute maximum you can draw from USB is 1.2A i.e. 6W

You NEED a powered drive.

  • Or a powered HUB. Mar 25, 2022 at 22:28
  • Actually, the aforementioned NASPi case uses a SATA Storage Shield, which I believe powers the drive over the power supply. So I think this should not be the problem.
    – Roysten R.
    Mar 26, 2022 at 1:10
  • @RoystenR. which should be in your question. You can't expect everyone to know all the hardware.
    – Milliways
    Mar 26, 2022 at 1:30
  • @Milliways Yes that is true, my bad. I guess I should not have written "SATA adapter", but rather "SATA Storage Shield ...".
    – Roysten R.
    Mar 26, 2022 at 1:34

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