raidz2 math

Discussion in 'New to FreeNAS?' started by rcrh, Apr 30, 2012.

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    rcrh

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    rcrh, Apr 30, 2012

    So I've created a raidz2 volume with seven 2tb drives. I was expecting to have 10tb of storage available after two of the drives were used for parity. But, Freenas is reporting only 8.3tb available. Is this marketing "rounding" caused because a 2tb drive is really only 1.8tb? Or, did I do something wrong?
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    cyberjock Forum Guard Dog/Admin

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    cyberjock, Apr 30, 2012

    My guess is rounding.

    If you had accidentally chosen 6 drives you'd have 8TB total(minus some for marketing "rounding").

    I'd say if you are sure your configuration is RAIDZ2 then all is well. I say this only because you are questioning your configuration and if you had chosen 6 drives on a RAIDZ1 you'd have the exact same amount of space free.
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    ProtoSD FreeNAS Guru

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    ProtoSD, Apr 30, 2012

    You'll get better performance with either 6 or 8 disks and RAIDz2. Even numbers of disks for RAIDz2 (4,6,8), odd numbers for RAIDz1 (3,5,7).
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    rcrh

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    rcrh, Apr 30, 2012

    Nope. Definitely seven drives in the case and all are in the one volume.

    Thanks for the succession.
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    rcrh

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    rcrh, Apr 30, 2012

    Shoot. I forgot about that guidance. I tell ya, the small amount of data I've moved to the volume so far has been incredibly slow. I may pull the plug and rebuild it with size discs.

    Thanks.
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    gpsguy Active Member

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    gpsguy, Apr 30, 2012

    At the end of the day, your 3.5Gb? of RAM, is a contributing factor to your performance issue.

    How are you transferring the data? If CIFS - read the various threads about it. On my Gb LAN, using FTP is about twice as fast as CIFS.
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    StephenFry FreeNAS Aware

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    StephenFry, May 1, 2012

    It's what I did; go for six (or if you're brave, ten) disks. Eight isn't ideal either.
    Performance will be excellent with both 6 or 10 - mine is so fast now that either the Gbit line or source HDD are the bottleneck. And yes, that's using CIFS.

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