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I own several (cheap, but original) 32GB Kingston USB3 Datatraveler pendrives, and I tested all of them as USB root devices (either with or without USB boot, some of them work everywhere, others boot on some RPi's and don't on the rest and need the SD, but that's another story). Datatraveler G4's seem consistent between Windows and Raspbian, at 7+MB/s. I have a DT50 which runs faster than the G4 both on Windows and Raspbian, and another that runs fast on Windows, but stops at less than 3MB/s on Raspbian. I owned a DT100G3 which ran fast on Windows, and at less than 2MB/s on Raspbian (I returned that one).

By "fast on Windows" I mean achieving above 15MB/s write speed in real life write benchmarks (h2testw for real capacity testing, which I do on every removable media that passes through my hands). By "slow on Raspbian" I mean that the speeds I reported above, are calculated by running:

 dd if=/dev/zero of=test bs=1048576 count=200

My fleet is made of 3 RPi3B, 1 RPi3B+, and 1 RPi4 4GB (this last one I tried with the "slow" DT50, which I didn't test on the other RPi's; the Datatraveler G4 that ran on the 3B+ and was then moved to the 4B kept the same speed between the two models).

Is this the hardware just being iffy, and I can do nothing about it, or is there something I can tweak somewhere to get in Raspbian the same speed that I get in Windows out of these pendrives?

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  • dd is very, very slow, and not good for performance tests. What do you get from sudo hdparm -tT /dev/sda ?
    – sweber
    Sep 30 '19 at 9:10
  • @sweber I have since then removed the pendrive from the system so it would be impractical for me to replace it in order to test with hdparm, yet the same test yielded normal results with other pendrives, I'm talking about 7, 12, even 20MB/s, just with this one it's 2MB/s even if under windows it's totally another story as it reaches almost 20MB/s
    – ephestione
    Sep 30 '19 at 15:51
  • @sweber I'd be interested in a reference for that; a userland read is mostly a userland read, is a userland read. It (dd) perhaps has a significant sweet spot WRT block size -- although that is a very crude test, dd if=/dev/zero of=/dev/null bs=512M on a Pi 4 reaches ~5 GB/s. So it should easily keep up with the hardware. The OP's is not a false test.
    – goldilocks
    Feb 3 '21 at 20:06
  • The fact that the stick could be tested on Windows implies it might be a filesystem type issue. If you are using a proprietary FS, the open source implementation used on the Pi is bound to be sub-optimal.
    – goldilocks
    Feb 3 '21 at 20:09
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    Sorry, I have since then stopped using that pendrive, and if I'm not wrong I might have found a workaround by adding some dtoverlay directives in the config.txt which I don't remember,as having stopped to use that pendrive I removed from the config.txt so have no trace as of what they were
    – ephestione
    Feb 7 '21 at 13:46
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Agreed, Kingston DT100G3 barely goes above 1 Mb/s on Raspberry Pi. I found this the hard way after after tearing Deluge apart for more than 8 hours for slow download speeds.

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  • Since your experience is more recent that the original question, do you mind checking for UAS errors (e.g. sudo dmesg | grep uas)? Feb 15 '21 at 11:54

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