This page gives some hints and optimizations you can make to tune your MINIX 3 system to match your requirements.
If you have a large memory, you may also wish to increase the size of the file system buffer cache. To do this, change the value of the constant NR_BUFS in servers/mfs/Makefile. This value tells how big the cache is in disk blocks (normally 4 KB), so a value of, say, 4096, creates a 16-MB cache. Then rebuild and reboot the system.