USB Flash Disk

Navio / Edge Hardware
1

Hi

I am testing the write speed of a USB flash disk, and the results are very poor (also getting kernel panics occasionally):

  dd count=100 bs=1M if=/dev/urandom of=/mnt/usbdisk01/test
  100+0 records in
  100+0 records out
  104857600 bytes (105 MB) copied, 95.6082 s, 1.1 MB/s

Is this due to the limitation of the realtime kernel?

From top, I can see dd saturating one of the cpu cores:

Tasks: 119 total,   2 running, 117 sleeping,   0 stopped,   0 zombie
%Cpu0  :  2.2 us,  2.2 sy,  0.0 ni, 95.5 id,  0.0 wa,  0.0 hi,  0.0 si,  0.0 st
%Cpu1  :  0.0 us,  9.2 sy,  0.0 ni, 90.8 id,  0.0 wa,  0.0 hi,  0.0 si,  0.0 st
%Cpu2  :  0.0 us, 11.1 sy,  0.0 ni, 88.9 id,  0.0 wa,  0.0 hi,  0.0 si,  0.0 st
%Cpu3  :  0.0 us,100.0 sy,  0.0 ni,  0.0 id,  0.0 wa,  0.0 hi,  0.0 si,  0.0 st
KiB Mem:    883716 total,    83204 used,   800512 free,    11872 buffers
KiB Swap:        0 total,        0 used,        0 free,    37876 cached

  PID USER      PR  NI  VIRT  RES  SHR S  %CPU %MEM    TIME+  COMMAND
 2460 root      20   0  6288 3676 2716 R  86.7  0.4   0:11.81 dd
   67 root     -51   0     0    0    0 S  15.7  0.0   2:10.30 irq/75-dwc_otg_
   65 root     -51   0     0    0    0 S  14.1  0.0   2:05.51 irq/75-dwc_otg
   66 root     -51   0     0    0    0 S  11.5  0.0   1:36.63 irq/75-dwc_otg_

Regards
Keith

2

Please ignore, I have changed the test to use /dev/zero, not quite the best test, but it removes the bottleneck from dd.

3

Along similar lines switching from Class 10 or U1 SD cards to U3 (recently dropped in price from SanDisk and Samsung) differs from about 25mb/s to 95mb/s write. Maybe you don’t need a stick and can save space if an upgraded SD will do. Assuming you’re not using some crazy big USB memory stick beyond the reasonably priced U3 SD cards.

4

I am planning to store recorded video/audio to the USB disk, so it is really more for robustness. Ie USB stick dying will not kill OS running on SD…