Blisteringly Slow HDD read/write over nfs mount

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Blisteringly Slow HDD read/write over nfs mount

Postby jbenge1 » Tue May 15, 2018 4:15 am

I recently installed archarm on my Rpi3, and I mounted a 500gb HDD to it using a sata to usb adapter. The only issue is that whenever I mount it to my main laptop as an nfs, and I try to read/write to it, it is unbearbly slow as in several days for ~1gb. Is the Rpi3 just naturally this slow? Maybe it's important to mention as well that whenever I am connected to a monitor via hdmi, and I bump the desk or move the rpi, i get a voltage error and after a few moments < 1s it says voltage normalized (or something along those lines). Could this be the cause of the slow read/write?

Also if it's important to note whenever the hdd is connected to another laptop and again I have it mounted as an nfs to my main laptop, read/write operations are slow, but not a few days for ~1gb.
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Re: Blisteringly Slow HDD read/write over nfs mount

Postby WarheadsSE » Tue May 15, 2018 2:37 pm

1) RPi3 has 10/100Mbps Fast Ethernet over USB2. This limits you to a maximum of ~12MB/s raw over the network.
2) The drive is attached to USB2, which will lower overall performance to ~30MB/s max without contention
3) The ethernet and USB ports share the same root hub, thus contend. The more you push the network, the less performance of disk will be, and vice versa.
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Re: Blisteringly Slow HDD read/write over nfs mount

Postby jbenge1 » Tue May 15, 2018 4:40 pm

Hmm the Rpi is connected via wifi so there shouldn't be any contention right? But it seems to me that using the Rpi as an nfs server maybe isn't viable? Also thanks for the reply/information :D
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Re: Blisteringly Slow HDD read/write over nfs mount

Postby WarheadsSE » Tue May 15, 2018 5:29 pm

The wifi is still not going to get you gigglebit speeds (~112MB/s raw, at perfect) due to how the technology behaves, in combination with how the wifi is actually attached to the SoC. I would expect , at best, to be limited to half of that. You're then limited within the wifi -> soc -> USB -> drive chain, which still smacks you in the face with ~30MB/s maximum. You're likely to see closer to 18-24MB/s on smaller files.
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