P33M

What happens if you use a powered USB3 hub between the Pi and the SSD?

One possibility is a malformed packet over PCIe is causing target or completer aborts (which the xhci controller generally can't recover from). One way in which this can happen is...

I suppose the acid test would be to swap the Pi4 board for another, keeping all other components exactly the same (and the same VLI firmware version), and seeing if...

Well at least that should eliminate a hardware fault within the Pi as a cause. "Crashes randomly after 1-2 days" isn't going to be reproducible here. One thing I note...

How are you resolving the Pi's IP? Hostname? What happens if you try to ping the (known) IP address instead of trying to resolve the host?

Plug an optical mouse into one of the spare USB ports. When the crash occurs, does the LED on the bottom of the mouse turn off?

Do you have a powered USB3.0 hub, and if so, what is the behaviour with one or both SSDs plugged into the hub?

Yes. Popcornmix.

I tried playing with kmemleak today and it gave me nothing relating to mmc under the same conditions - other than some (what I assume to be spurious) warnings about...

It entered the same failure mode over the weekend. ``` root@raspberrypi:/home/pi# cat /sys/kernel/debug/swiotlb/io_tlb_used 32762 root@raspberrypi:/home/pi# cat /sys/kernel/debug/swiotlb/io_tlb_nslabs 32768 ``` No results in kmemleak. The leak actually takes around 20k seconds...