I have OpenWrt for many years on a TP-1043ND, with external root in USB sticks.
Now using CHAOS CALMER (15.05.1, r48532) because the latest LEDE release didn't have the wifi as stable as this one.
Anyway, from time to time (more or less every two years), the USBs get weared and I need to replace them.
Therefore, I'm trying to limit all te possible writes so I can extend the USB stick lifetime.
I've disabled some things such as the FW logging (lots of scann/login attempts) but I can't find where "logread" and "dmesg" is written. I'd be assuming it would be something in /var/log but it seems not.