@redpola It won't help with the upgrade but one can use a RAM disk for /var and /tmp. However, pfSense will copy data to disk during boots. There is a "Log Directory" time in hours, but even if left blank I suspect it will copy at restart. And of course for an unexpected boot you'd lose all logs at boot. And note their note:
"The size of the /var RAM disk, in MiB. The default value is 60, but should be set much higher, especially if packages will be used. 512-1024 is a better starting point, depending on the available firewall RAM and kernel memory."
...hence why 32 MB seems small.