USB 3.0 pendrive


Here is a raw read using dd of my 3tb drive inside the enclosure. As you can see, the speed looks good for this old spinner. However, real life usage is a different story.

rock@RockSvr:~$ sudo dd if=/dev/sda of=/dev/null bs=100M
^C32+0 records in
31+0 records out
3250585600 bytes (3.3 GB, 3.0 GiB) copied, 25.6378 s, 127 MB/s


I’ve run modprobe uas, also added uas to /etc/modules, put the pendrive in lower USB 3.0 port and restarted the board. lsmod gives that uas is loaded. I have script:

#!/usr/bin/env bash
echo === WRITE 1GiB ===
echo -n "sync..." ; sync ; echo "ok"
time {
        dd if=/dev/zero of=temp conv=fdatasync bs=1024k count=1k
        echo -n sync...
        echo ok
rm -f temp
echo -n "sync..." ; sync ; echo "ok"
echo Done.

which now gives:

=== WRITE 1GiB ===
1024+0 records in
1024+0 records out
1073741824 bytes (1,1 GB, 1,0 GiB) copied, 35,9079 s, 29,9 MB/s

real    0m35,940s
user    0m0,000s
sys     0m6,064s

Surely the pendrive achieves higher speeds on PC. However I don’t know much about this pendrive (chip, controller etc.).

EDIT: Just tested HDD in USB 3.1 enclosure. Acts up to 26.4 MB/s. On PC full write speed is about 120 MB/s.


Wow, you’re facing worse results than I am. What do you get when you run hdparm?

Timing buffered disk reads: 198 MB in  3.03 seconds =  65.45 MB/sec

That’s really strange, because it says that pendrive is in USB 3.0 mode at this speed. Should give about 140 MB/s read and 80-90 MB/s write…


While HDD write is up to 26.4 MB/s, reading is blazing fast! I’ve got over 124 MB/s constant read speed. Still pendrives are too slow…


Just thought I would add my unusual experience that may shed some light on a possible issue.
I have done quite a bit of speed testing (fio) with my Samsung EVO 970 250GB NVMe and for what ever reason after some random amount of testing the speeds drop by about 70% and nothing I do restores it. I have no explanation why this happens but formatting the drive fixes the speed problem. Drive is formatted with ext4.

Maybe you are having a similar issue?


I tried using the Debian image yesterday, and I see the same results. The speed is just too slow for my needs. Such a bummer.