Dietpi on rock64, better USB3 performance than Ayufan Stretch and Armbian Bionic!

[Adr3nal1n]

hdparm -Tt stats from Arch Arm for the USB3 connected SSD and HDD:

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/dev/sdc: (USB3 SSD - Samsung 840 Basic 120GB)
 Timing cached reads:   1860 MB in  2.00 seconds = 930.65 MB/sec
 Timing buffered disk reads: 1002 MB in  3.00 seconds = 333.59 MB/sec

/dev/sdb: (USB3 HDD - SAMSUNG HD204UI)
 Timing cached reads:   1774 MB in  2.00 seconds = 886.91 MB/sec
 Timing buffered disk reads: 394 MB in  3.01 seconds = 130.94 MB/sec

[MichaIng]

Ah jep, this is mostly the case. Always add SSDs/HDDs with dedicated power supply to an SBC. The USB power is not sufficient in most cases and/or decreases stability.

USB port mostly can only power reliably up to a USB stick and such.

[WarHawk]

I had to splice in a 5vdc power supply to my external drive on my nextcloud drive, otherwise it wouldn't spin up and it would crash my SBC...the RPi has a hack to make it output more power but it's easier to cut a cable and splice power into it or use a dedicated power supply for the drive...it provided proper power and is much more stable

[MichaIng]

On RPi, default max current on all USB ports together(!) is 0.6A (=3W), with max USB power setting (enabled by default on DietPi), it's increased to 1.2A (=6W).

But this might be different on Rock64, but still, even if the USB ports provided enough power, the PSU of the board might be insufficient.

[Fourdee]

On RPi, default max current on all USB ports together(!) is 0.6A (=3W), with max USB power setting (enabled by default on DietPi), it's increased to 1.2A (=6W).

But this might be different on Rock64, but still, even if the USB ports provided enough power, the PSU of the board might be insufficient.

Yep, i've had a few USB 2.0 slots on various boards, under power a 0.7A drive.
Which makes sense, as USB 2.0 standard is 0.5A max.

USB 3.0 seems fine, 0.9A. All SSD drives, and low power platter drives should also be fine.

[bronco]

Not sure how to check this.

Easy. Use

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sbc-bench -m

to monitor what's happening in another shell while running benchmarks (benchmarking without monitoring is pretty useless):

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wget https://raw.githubusercontent.com/ThomasKaiser/sbc-bench/master/sbc-bench.sh
chmod 755 sbc-bench.sh
sudo ./sbc-bench.sh -m

Since you're using a Rock64 you can also check whether DietPi deleted rock64_diagnostics.sh since if not you have my code already and can run

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rock64_diagnostics.sh -m

Results will then look like this (for more examples check links in right column here https://github.com/ThomasKaiser/sbc-ben ... Results.md):

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Time        CPU    load %cpu %sys %usr %nice %io %irq   Temp
05:38:47: 1392MHz  3.19  26%   7%  17%   0%   1%   0%  45.5°C
05:39:17: 1392MHz  3.14  78%   1%  76%   0%   0%   0%  56.8°C
05:39:48: 1392MHz  3.19  84%   1%  82%   0%   0%   0%  58.6°C
05:40:19: 1392MHz  3.38  85%   1%  83%   0%   0%   0%  61.7°C

This is a Rock64 with recent Armbian image (there I added the 1.4GHz cpufreq OPP but we did not allow for the 1.5 GHz settings since too many instability reports occured). With ayufan images you can dynamically load a DT overlay for the higher clockspeeds and since DietPi is just a modified userland on top of ayufan's work it should work here exactly the same (for details do a web search for 'ayufan DT overclock' or something like that)

SSDs with trashed performance is quite common when powered by SBC, the reason is usually undervoltage and not undercurrent (on almost all SBC USB ports there are current limiters in action exceeding the commonly known 500mA for USB2 or 900mA for USB3 -- ROCK64 allows 650mA on each USB2 port and 950 mA on the USB3 port but a RPi 3 uses 1.2A for all 4 USB2 ports combined or a NanoPi M4 for example has one global 2A current limiter for all 4 USB3 ports -- you always need to study schematics).

But as already said: usually it's undervoltage (cable/contact resistance between PSU and board and again between board and disk) causing the problems and not limited current (same on the RPi 3 where 1.2A are set by default -- compare with 'vcgencmd get_config int' output -- but due to Polyfuses and Micro USB powering the voltage available to USB peripherals often drops below 4.5V and then majority of external SSDs get in trouble, the majority of 2.5" HDD already has trouble with less than 4.75V)