Raspberry Pi 4 write speed in kb/s using USB-3 SSD?

Question

TLDR; USB-3 SSD on Raspberry Pi 4 has read speeds of 322KiB/s and write of 108KiB/s, expecting MB/s at least...

I've gone through every forum on this one, using this test:
sudo fio --randrepeat=1 --ioengine=libaio --direct=1 --gtod_reduce=1 --name=test --filename=test --bs=4k --iodepth=64 --size=4G --readwrite=randrw --rwmixread=75
I get these results:

test: (groupid=0, jobs=1): err= 0: pid=29327: Mon Oct 17 01:54:05 2022
  read: IOPS=80, BW=322KiB/s (330kB/s)(3070MiB/9752067msec)
   bw (  KiB/s): min=   32, max=  640, per=100.00%, avg=322.30, stdev=56.10, samples=19503
   iops        : min=    8, max=  160, avg=80.53, stdev=14.03, samples=19503
  write: IOPS=26, BW=108KiB/s (110kB/s)(1026MiB/9752067msec); 0 zone resets
   bw (  KiB/s): min=    7, max=  240, per=100.00%, avg=107.68, stdev=30.44, samples=19502
   iops        : min=    1, max=   60, avg=26.87, stdev= 7.61, samples=19502
  cpu          : usr=0.19%, sys=1.23%, ctx=1066066, majf=0, minf=18
  IO depths    : 1=0.1%, 2=0.1%, 4=0.1%, 8=0.1%, 16=0.1%, 32=0.1%, >=64=100.0%
     submit    : 0=0.0%, 4=100.0%, 8=0.0%, 16=0.0%, 32=0.0%, 64=0.0%, >=64=0.0%
     complete  : 0=0.0%, 4=100.0%, 8=0.0%, 16=0.0%, 32=0.0%, 64=0.1%, >=64=0.0%
     issued rwts: total=785920,262656,0,0 short=0,0,0,0 dropped=0,0,0,0
     latency   : target=0, window=0, percentile=100.00%, depth=64

Run status group 0 (all jobs):
   READ: bw=322KiB/s (330kB/s), 322KiB/s-322KiB/s (330kB/s-330kB/s), io=3070MiB (3219MB), run=9752067-9752067msec
  WRITE: bw=108KiB/s (110kB/s), 108KiB/s-108KiB/s (110kB/s-110kB/s), io=1026MiB (1076MB), run=9752067-9752067msec

Disk stats (read/write):
  sdc: ios=785603/312743, merge=310/2356, ticks=16335446/3116502, in_queue=17370112, util=100.00%

System setup is 64-bit Ubuntu (kernel 5.4.0-1071-raspi) on raspberry pi 4 hardware, have confirmed I'm "using xhci_hcd" driver from dmesg, no errors as well.

Tried adding "usb-storage.quirks" for the device in cmdline.txt as well with no change..

SSD is

[436294.004115] usb 2-2: Product: Elements 2621
[436294.004126] usb 2-2: Manufacturer: Western Digital

Anyone else seeing this with their Pi 4 setup that can help??

Answer 1

You are doing randrw, which is of course much slower than sequential rw operations, especially on a spinning HDD and even more over USB.

From the fio documentation:

 readwrite=str, rw=str

    Type of I/O pattern. Accepted values are:

        read
            Sequential reads.
        write
            Sequential writes.
        trim
            Sequential trims (Linux block devices and SCSI character devices only).
        randread
            Random reads.
        randwrite
            Random writes.
        randtrim
            Random trims (Linux block devices and SCSI character devices only).
        rw,readwrite
            Sequential mixed reads and writes.
        randrw
            Random mixed reads and writes.
        trimwrite
            Sequential trim+write sequences. Blocks will be trimmed first, then the same blocks will be written to. So if io_size=64K is specified, Fio will trim a total of 64K bytes and also write 64K bytes on the same trimmed blocks. This behaviour will be consistent with number_ios or other Fio options limiting the total bytes or number of I/O’s.
        randtrimwrite
            Like trimwrite, but uses random offsets rather than sequential writes.