After moving the root partition of an Raspbian installation from memory SD card to USB flash drive, as described here, I encountered significantly improved performance in some cases, but timeouts and really bad performance in others. Investigating the system logs with
revealed numerous of the following messages
[...] kernel: [...] usb 1-1.3: reset high-speed USB device number ... using dwc_otg
Searching this error message online, the first thing that caught my eye was that most of the prominent results are related to the Raspberry Pi, such as this one here.
These discussions relate above error message to power issues with connected USB devices. I am using a Transcend Jetflash 600 USB pendrive, that reports a maximal amperage of 100 mA with
The Raspberry Pi provides this amperage on its USB ports, though it is the maximum current that may be drawn from the USB ports (please note that this is under-spec, with standard USB ports specified to provide 500 mA). Anyway, as things are, the USB pendrive seemed to use more power than it reports and than the USB port could provide.
As I was using a single USB port of the Raspberry PI only, I decided to use both USB ports to power the USB flash drive (An alternative would be an active USB hub – an option I did not pursue any further). For this purpose, I used a so called USB Y cable. This provides two USB A plugs (one for power and data, one for power only), that connect to a single USB A socket (to which the USB pendrive is connected in our case).
These cables are very cheap, you might have one at home or find one as cheap as for 2 EURs online. Using a USB Y cable resolved the power issues with the Transcend Jetflash 600 cable on my Raspberry PI. Now, the move of the root partition to an USB flash drive provides unlimited benefit.