Memory File System

Digital UNIX Version 4.0 supports a Memory File System (MFS) which is essentially a UNIX File System that resides in memory. No permanent file structures or data are written to disk, so the contents of an MFS file system are lost on reboots, unmounts, or power failures. Since it does not write data to disk, the MFS is a very fast file system and is quite useful for storing temporary files or read-only files that are loaded into it after it is created.

For example, if you are performing a software build which would have to be restarted if it failed, the MFS is a very appropriate choice to use for storing the temporary files that are created during the build, since by virtue of its speed it would reduce the build time. For more information, see the newfs(8) reference page.