GEOM is the new disk I/O subsystem in FreeBSD 5.x. It provides an extensible and modular framework for “doing things” to disk I/O requests. It allows you to recognize Apple partitions on your PC and Solaris partitions on your Alpha, mirror your striped disks, stripe your mirrored disks, and even stripe your encrypted, mirrored Apple partitions on your Sparc64 computer.