ZFS on Linux: It's alive

A hot feature from OpenSolaris is taking a weird but working path to Linux inclusion

By Don Marti, LinuxWorld.com, 06/18/07

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If you like Linux for the long list of supported hardware but Solaris for the advanced new ZFS filesystem, a new development project might have a happy surprise for you.

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ZFS on FUSE

FUSE -- implementing filesystems in user space

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Sun's ZFS filesystem offers storage administrators a new level of simplicity. Instead of using what on Linux are separate software RAID, logical-volume-management and filesystem layers, ZFS combines the three into a single layer that’s easier to administer.

ZFS also has new data-checking and repairing techniques to keep administrators from going through time-consuming and risky runs of the fsck filesystem checker utility. In mail to the linux-kernel mailing list, Linus Torvalds called ZFS one of the "very few bright spots" in Solaris.

But there's a catch. ZFS, like the rest of OpenSolaris, has been available under Sun's Common Development and Distribution License for about two years, and Linux has been under Version 2 of the the GNU General Public License since its first release in 1991. The licenses are incompatible.

One programmer, Ricardo Correia, has what could be an answer, however. A technology called Filesystem in Userspace (FUSE), introduced in the 2.6.14 kernel released in October 2005, enables Linux to use filesystems that run as ordinary processes. FUSE already hosts an implementation of the NTFS filesystem, NTFS-3g, that runs with decent performance.

In a project originally funded under Google's 2006 Summer of Code program, Correia has converted the ZFS implementation from OpenSolaris into a server or daemon program that runs on Linux.

The project is working, with several users running and even booting from a ZFS volume. Correia has not undertaken any performance tuning yet, and one sysadmin, Chris Samuel, has posted benchmarks that clock only about half the speed of another Linux filesystem, XFS.

NTFS-3g, however, has results comparable to a native Linux filesystem, so "at least NTFS-3g does show that good performance is quite possible for a FUSE filesystem," Samuel says in an e-mail interview.

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