Absolute OpenBSD, 2nd Edition

Memory Filesystems

In addition to creating partitions on raw disk, OpenBSD lets you create partitions in system memory. A memory filesystem (MFS), or memory disk, lives in your machine’s RAM, rather than on a physical disk. Reading and writing files to and from such a filesystem is much faster than accessing those same files on a spinning disk, which makes a memory-backed filesystem a huge optimization for certain applications.

If MFSs sound too good to be true for high-performance environments, that’s because they are. Understand their limits before you implement them everywhere. First, RAM does not persist across reboots or shutdowns, so either will erase the contents of an MFS. While this might seem obvious, I’ve surprised myself more than ...