FWIW. 256MB should handle the latest OpenBSD, with little issue (although an upgrade to 512MB wouldn't hurt if possible). The main issue is going to be pf.conf

FWIW. 256MB should handle the latest OpenBSD, with little issue (although an upgrade to 512MB wouldn't hurt if possible). The main issue is going to be pf.conf syntax. OpenBSD has become a little bit more RAM intensive on boot recently due to relinking shared libraries and the kernel to randomize them (Think .o level ASLR), but 256MB IIRC can handle it. Boots will be slow, but if you've dealt with 6 year uptimes in the past that probably won't lead to much of an issue.