File I/O operation ties up the system on RPI4

I have noticed that intensive file reading or writing especially tend to tie up the system completely. It seems RPI4 is only single threaded while performing I/O because Other GUI operation such as loading webpages in browser hangs or slow down a lot until the I/O finish or stop. For example, if Thunderbird mail client is fetching the emails in the background, then simultaneously loading webpages in Firefox take a very long time which normally is extremely fast. Will mounting home directory on an external SD drive help or something else?

Please provide output of

inxi -SMIza

Have you analyzed output of



actually, I’ve figured out the problem is due to Thunderbird hogging up the CPU resource when I analyze disk I/O using btop and thunderbird running in background

There is a marked performance improvement using a web browser with a ssd because of a lot of writes to the drive occur while browsing. Probably not so much with a cpu / memory hog running at the same time though.

I do not check my email with the rpi. Even google web mail is horrible with using the resources. If you have to check your mail on the rpi I would try one of these to see if it is better.