"Linux has an interesting relationship with file systems.
Because Linux is open, it tends to be a key development platform
both for next-generation file systems and for new, innovative file
system ideas. Two interesting recent examples include the massively
scalable Ceph and the continuous snapshotting file system nilfs2
(and of course, evolutions in workhorse file systems such as the
fourth extended file system [ext4]). It's also an archaeological
site for file systems of the past—DOS VFAT, Macintosh(HPFS),
VMS ODS-2, and Plan-9's remote file system protocol. But with all
of the file systems you'll find supported within Linux, there's one
that generates considerable interest because of the features it
implements: Oracle's Zettabyte File System (ZFS).
"The ZFS was designed and developed by Sun Microsystems (under
Jeff Bonwick) and was first announced in 2004, with integration
into Sun Solaris occurring in 2005). Although pairing the most
popular open operating system with the most talked-about,
feature-rich file system would be an ideal match, licensing issues
have restricted the integration. Linux is protected by the GNU
General Public License (GPL), while ZFS is covered by Sun's Common
Development and Distribution License (CDDL). These license
agreements have different goals and introduce restrictions that
conflict. Fortunately, that doesn't mean that you as a Linux user
can't enjoy ZFS and the capabilities it provides.
"This article explores two methods for using ZFS in Linux. The
first uses the Filesystem in Userspace (FUSE) system to push the
ZFS file system into user space to avoid the licensing issues. The
second method is a native port of ZFS for integration into the
Linux kernel while avoiding the intellectual property issues."