Why you want ZFS for Linux

Posted by Kaya Kupferschmidt • Saturday, January 6. 2007 • Category: Hardware
Currently I am thinking of replacing my (rather new) ReadyNAS NAS server by a more powerful self-built server. Although the ReadyNAS is a very nice device with very good support from Infrant, it is still too slow for storing all remotely mounted user directories for my Linux and Mac box. Plus I am thinking of using a iSCSI volume for all user directories on my Windows box.

My ideal server would contain an Areca SATA controller with 16 channels and 15 disks in hot-swap carriers running in a RAID-6 plus one or two fast gigabit controllers. So much for the hardware.

But another important aspect is the software of course. Currently I would opt for OpenFiler as operating system for the server. OpenFiler is based on Linux and supports all features I want, except for efficient snapshots. Snapshots are a wonderful thing, they allow to keep an old state of a file-system without the need to do an explicit backup (although one still should backup ones data because of the risk of hardware faults). OpenFiler implements these snapshots using LVM (Logical Volume Manager), which in turn implements snapshots on a Copy-on-Write base. This snapshot implementation has two main drawbacks:
  • You have to allocate space for the snapshot on your disks.

  • The more snapshots you have, the slower gets your system .

And this is exactly the point where Suns filesystem ZFS comes in. ZFS also supports snapshots, but as it seems in a much more efficient way. You do not need to preallocate space for the snapshot and it seems that there is no performance penality by using them. So I'd love to use ZFS together with OpenFiler - but ZFS currently is only available in Solaris with a Linux port under the way. But I guess it will take more time for the Linux port to finish and to be integrated into OpenFiler than I want to wait with my new NAS server.

Snapshots really are the reasons why everyone wants ZFS on Linux. Okay, at least this is my personal top reasons why I want to see it soon. Or a port of OpenFiler to Solaris ;-)


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  1. *Or maybe simply buy yourself a real server (SUN) with a real OS and not something homebrewn with a bastel os done by longhaired opensouce communists.

    C U

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