What's the best ZFS raidz1 configuration for 8 disks

Discussion in 'Storage' started by jlray, Jul 17, 2012.

  1. jlray New Member

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    jlray, Jul 17, 2012

    I read from the wiki that ZFS raidz1 starts with 3 disks and works best with 8 disks.

    If I have 8 disk and I don't care how many volumes to have, what is the best scenario?
    1. create one ZFS raidz1 volume over 8 disks
    2. create one ZFS raidz1 volume over 3 disks; create another ZFS raidz1 volume over 5 disks

    Any CON and PRO?

    Thanks.
  2. paleoN Active Member

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    paleoN, Jul 17, 2012

    You miss understood. The optimal raidz1 vdevs are 3, 5 or 9 disks. IMO, 9 disks are at least 4 disks too many to be considering a single-parity array.

    What are your storage requirements and why do I keep asking this question?

    Without any additional information I would say create a raidz2 volume of 6 disks and keep the other 2 as cold spares.
  3. jlray New Member

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    jlray, Jul 18, 2012

    Hi PaleoN,

    Thanks for your reply. I'd like to get the maximum space out of my 8 disks. Speed/performance is not a concern.

    I will use the storage for home sharing and that's why I don't think 2 disks will fail at the same time as the loading is not high, or am I wrong here?
  4. sska New Member

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    sska, Jul 18, 2012

    not quite, but by replacing the load will be hight and there is a chance... to lose all your data...
    I, personally, have changed two disks in my pool - this did not happen - and i'm happy... but 16-20 hours for disc replacement in 4x1.5TB pool... can all happen.
  5. jlray New Member

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    jlray, Jul 18, 2012

    Then probably I will go with raidz2 so I can survive with two discs failing without data loss and it will give me 6 discs of space. How does that sound?

    Currently I'm using one 3T disc in UFS and one 3T disc in ZFS, just to get myself familier with FreeNAS. I found CIFS share is faster on UFS than on ZFS (write speed 90+M/s over 60+M/s). Is this expected? Is it because I'm using one disc ZFS? I'm using AMD CPU on board with 8GB memory.
  6. paleoN Active Member

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    paleoN, Jul 18, 2012

    It sounds fine. I would still have at least 1 cold spare on hand for when you do get a disk failure.

    Rebuild times are way to long for 3TB disks. I would only consider running them in a mirror or double-parity, raidz2.

    I didn't see it with my setup, both maxed out at 70M/s. :( It can depend on what version of FreeNAS you are using and how you performed the tests. This [thread=5338]sticky[/thread] has some CIFs tuning settings. Do note not all of those settings are necessary.
  7. jlray New Member

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    jlray, Jul 19, 2012

    By code spare, you mean having the 9th disk on hand but not installed in the system so that it could be used to replace a failure disk should it happen, right?
  8. sska New Member

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    sska, Jul 19, 2012

    I think yes

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