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ZFS in Snow Leopard offers advanced features

updated 04:55 am EDT, Mon June 23, 2008

ZFS in Snow Leopard

Amongst a host of high profile releases and announcements at this year's WWDC, Apple finally confirmed what has been an open secret for over a year -- Suns ZFS filesystem is coming to Mac OS X 10.6 codenamed 'Snow Leopard'. Overshadowed by some of the more headline=friendly developments such as improved multicore support, OpenCL and 'Grand Central', ZFS support could turn out to be one of the most important developments in OS X.

So what exactly is ZFS? In short, ZFS is a fundamentally new approach to data management, developed from a blank page over seven years ago by Sun Microsystems, and subsequently released to the open-source community under a CDDL (Common Development and Distribution License). It offers a multitude of significant improvements over current filesystems (including Apple's own HFS-based setup):

- True end-to-end integrity by means of a 'tree-based' 128-bit checksumm system that verfies and corrects hidden data corruption anywhere in the data path...on the fly -- every block of data is checksummed and repaired as needed;

- Copy-on-write transactions eliminating disk corruption. Each block of data on a drive is checksummed continually against an established 'checksumm tree' and corrected as necessary not only on the host drive, but also on any mirrored or RAID drives that have a copy of the data. There is no need to ever FSCK (check or fix for file corruption) a ZFS filesystem drive.

- A pooled storage model that eliminates the need for drive partitions, provisioning or stranded storage, while also making use of all the combined I/O bandwidth of all devices attached to a machine;

- live disk-scrubbing -- similar to EEC memory, disk scrubbing is a complete read of all storage blocks, that is then compared to a 128-bit checksum tree, and errors corrected while the storage devices are in use;

- RAID-Z -- similar to RAID 5 but using a variable 'strip width' to avoid stripe corruption common with come common RAID 5 setups (due to loss of power between data and parity updates. (Opensolaris users have noted that "there's no read-modify-write tax, no write hole, and -- the best part -- no need for NVRAM in hardware").

- 'Snapshot'-based backup solution. A more advanced version of OS X 10.5's 'Time Machine' technology. Data is incrementally transferred to an 'image' every 10 seconds, providing a constant snapshot of your system. This snapshot can be used to fully backup machines, provide incremental backups as well as for remote imaging and replication.

ZFS represents the 'next step' in filesystems, and can only be seen as the long term successor to Apple's current HFS (Plus) implementation, according to an Apple spokesperson: "For business-critical server deployments, Snow Leopard Server adds read and write support for the high-performance, 128-bit ZFS file system, which includes advanced features such as storage pooling, data redundancy, automatic error correction, dynamic volume expansion, and snapshots".

by MacNN Staff



  1. 64stang06

    Joined: Dec 1969



    Please MacNN, make sure you put the word "server" in the title, or at least the first paragraph. This is ONLY coming to 10.6 Server (or at least that's what the marketing page for Apple makes it seem). Finding the word "server" in the last paragraph almost makes it sound as if Apple is giving this to the consumer market as well.

  1. testudo

    Joined: Dec 1969



    if history is any indicator, it probably will exist in OS X, just not have a nice and simple UI to enable/use it.

    Comment buried. Show
  1. testudo

    Joined: Dec 1969



    and as for this:
    It offers a multitude of significant improvements over current filesystems (including Apple's own HFS-based setup):

    Many people would argue that most current filesystems are significant improvements over HFS .

  1. neondiet

    Joined: Dec 1969


    root support

    As it stands ZFS root filesystem support in OS X isn't there yet. So HFS will still be required to boot, unless Apple can get that included in time. It's also not a Cluster Filesystem, so, users of Apple's Xsan filesystem won't get a look in; unless Apple work out how to layer Xsan on top of ZFS as Sun are planning to do with the Lustre filesystem.

  1. tyco

    Joined: Dec 1969


    yes finally

    yes finally

  1. Chopper3

    Joined: Dec 1969


    Please be aware...

    ...that Sun is currently being sued by NetApp, NetApp claim that Sun stole significantly from their own code - and they look to have a strong case that could impact this development.

  1. Bartman

    Joined: Dec 1969


    what about WinFS

    Apple is smarter than MS by licensing cool technologies rather than reinventing the wheel and forcing it down everyone's throat.

  1. webraider

    Joined: Dec 1969


    I just Wish

    They would implement the features of Disk Utility into the Finder like they did with OS 9. I should be able to re-format rewritable media by right-clicking on it. I should also be able to make an image of it the same way. This is one way that I feel Windows is more intuitive.

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