Oddbean

That kinda sounds more plausible to me but CPU is 70-80% idle. Also there is 80% of the RAM unused. I mean the setup is simple, it‘s a Raspi5 with 8GB of RAM and an external Storage… still it seems not all available resources are used 🤷🏻‍♂️

In that case the most likely problem is your SSD's throughput. Make sure you're using a very fast SSD with the proper high throughput cable. You can test your drive's throughput to verify this is the issue. Beyond that, it's your network.

Indeed it is, it’s an NVMe in an enclosure. Sadly I had to attach it to an slower USB2.0 port as umbrelOS was failing to start (boot loop) when connecting it to the faster USB3.0 port. But also here it does not sound that logical to me that the first 600GB could be stored quickly and for the comparable small rest it takes way longer 🤔 Network (bandwidth) with my ISP usually also is stable. But okay, maybe I‘ll just be a bit more patience 🙏. Thanks for your hints, tho!

This is almost certainly the problem, disk IO speed. Also the fact that your system is reporting low ram allocation that doesn't mean it's not doing paging. The OS may not be using all the available ram, and it may be reserving parts of it. You can try using iostat and iotop to monitory what's going on. Also check your memory usage settings. and if possible adjust your cache size. My money is on your disk is just too slow. And remember that when something is bottlenecked it can run perfectly fine until the straw that broke the camel's back comes along and you go from running fine to massively bottlednecked and paging like crazy.