Apple Dumps ZFS, as File Systems Battle Heats Up

Most actions have unexpected consequences. One of unexpected consequences of Oracle's move to buy Sun Microsystems earlier this year may be Apple's decision last week to abandon ZFS.

OS Roundup: Apple last Friday announced ZFS would not be making an appearance in Snow Leopard. An interesting choice, given that some believe when the Sun-Oracle deal closes, the new entity may have the two most powerful file systems around.

ZFS, you'll recall, is Sun's open-source file system, and as file systems go it's quite simply the badger's nadgers: If you want a high-capacity file system with continuous data integrity checking, copy-on-write, highly space efficient snapshotting and cloning and plenty more besides, then ZFS is for you. It's a hard core, enterprise-grade file system licensed under the CDDL.

When Apple's Leopard was released in 2007, it shipped with a basic read-only ZFS driver, and the buzz in the orchard, planted by none other than Sun CEO Jonathan Schwartz, was that ZFS would become the file system for OS X in a future release.

But when Snow Leopard arrived last August, there was no sign of ZFS: The rudimentary support found in Leopard had disappeared, and Apple kept its own council on the subject.

Until now, that is. Last Friday, the following announcement was made on Mac OS Forge:

ZFS Project Shutdown The ZFS project has been discontinued. The mailing list and repository will also be removed shortly.

And that was it. It's not clear from this rather terse message why Apple has abandoned ZFS, but Jeff Bonwick, who lead the team at Sun that developed ZFS, offers a clue. Commenting on a post on the zfs-discuss mailing list speculating that Apple wanted a "private license" from Sun (with appropriate technical support and indemnification), Bonwick replied: "I cannot disclose details, but that is the essence of it."

NetApp is currently suing Sun for patent infringement over ZFS, and this sounds like Apple has been put off adopting ZFS to replace its aging HFS+ (first introduced in 1998) for fear of ending up falling foul of this patent dispute. Oracle has its own Linux file system (BTRFS) under development anyway, and it may be unwilling to indemnify Apple for using ZFS if it offered Apple some sort of "private license."

Which leaves OS X with HFS+. Of course, Apple is not alone in using a venerable (i.e., old) file system. Microsoft's brand new Windows 7 was released just last week, yet it uses a version of NTFS, a file system originally designed for Windows NT back in the early 1990s. Both NTFS and HFS+ have been improved since they first appeared (the version of HFS+ in Snow Leopard introduces per-file compression, for example), but neither has the same scalability or automatic error correction facilities (and more) ZFS offers.

Snow Leopard and Windows 7 aren't the only OSes launching now: Thursday will see the launch of Ubuntu 9.10 Karmic Koala, the latest desktop and server version of Canonical's Linux distro. Karmic is the odd one out of the three because it has a new file system: New installs will make use of ext4, the successor to ext3, which was declared stable late last year. Existing Ubuntu installations will be upgraded, but the file system will not be changed from ext3

Note though that ext4 isn't exactly new underneath the hood. Ted Ts'o, CTO of the Linux

Foundation and the ext4 file system maintainer, dismisses ext4 as a rehash of outdated "1970s technology" and describes it as a conservative short-term solution. Talking at the Linux Collaboration Summit in San Francisco in April he said that the way forward would be — you guessed it — Oracle's Btrfs!

Apple's abandonment of ZFS may be one unexpected consequence of the Oracle-Sun deal, but if Ts'o is right, this means there's another consequence that wasn't obvious when the acquisition was first mooted: Oracle controls Sun, which has ZFS expertise, and Oracle controls Btrfs as well. Good file systems take a long time and much expertise to develop, and now Oracle has close ties to two very promising ones.

Who spotted when the Oracle-Sun deal was first announced that, that when it comes to enterprise file systems, Oracle would be putting itself in a strong position to take over the world?

Paul Rubens is a journalist based in Marlow on Thames, England. He has been programming, tinkering and generally sitting in front of computer screens since his first encounter with a DEC PDP-11 in 1979.

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This article was originally published on Oct 27, 2009
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