newb question: mix'n'match drives?

Discussion in 'Storage' started by joeblow, Apr 26, 2012.

  1. joeblow New Member

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    joeblow, Apr 26, 2012

    Greetings,

    I understand that for the drives that the ZFS is on, it's best that they are all the same size, same drive type. I also understand that the number of physical disks in a ZFS array cannot be dynamically changed. For example, start with 3 physical drives, 3 drives is what it is now and forever more.

    However, budget won't support that now. Can I use different size drives as 'placeholders' until such time as I can get proper drives?

    Details:

    I've got a case I can put 5 drives in.

    I have two 2TB drives on the way. I also have two 1.5 TB drives and one 1.0TB drive that I can use, so five drives would be:

    2 ea 2TB
    2 ea 1.5TB
    1 ea 1.0TB

    The idea is to set up the ZFS pool with these, then each month order another 2TB drive and replace a drive until all five physical drives are 2TB drives.

    Is this reasonable? Or am I not understanding how things actually work?

    Thanks!
  2. Kimba New Member

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    Kimba, Apr 26, 2012

    The problem is that all drives need to be upgraded to a larger size in order that the pool gets resized.

    Also the smallest drive would be the multiplier: For example if you use a RaidZ1 you use this formula ((# of Drives) - 1) * smallest drive space. With your setup it would be 5 TB.

    At this point there are thousands of ways to do this right so what I would do is create a pool of 2x1.5 TB and 1 x 1TB (3 drives) then just for practice swap out the 1 TB drive with the 2TB and resilver it.

    When you are done then repeat the process with the other 2 TB drive.

    When you get the third drive repeat the process and reboot the box. Now you can use the other three drives to create another pool of 3 drives and repeat the process you did with the first pool

    Remember mine is just a suggestion others will very
  3. ProtoSD Active Member

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    ProtoSD, Apr 26, 2012

    Joeblow,

    Kimba's suggestion is fine, but yours will work also. The trouble with Kimba menthod is if you're make a raidz1, then both of those 3 disk vdevs in the pool will each have their own parity disk, so you loose 2 disks to parity. Also, if one of those vdevs dies (2 disks in the same vdev fail), then you loose everything!

    I would prefer your way if you don't mind your pool being a little smaller until you replace the smaller disks. Remember, you must replace one disk at a time and let it resilver before doing the next disk. The process of resilvering is automatically triggered when you do a "zpool replace" on a disk.
  4. Fpmurphy New Member

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    Fpmurphy, Aug 10, 2012

    I've been searching the fourms, and have a similar question. I thought it was related enough to not start a new thread.

    I have a FreeNAS build that uses 2x1.5TB and 3x1TB drives in a raidz2. I'm using FreeNAS-8.2.0-RELEASE-p1-x64.

    I currently have 2.4TB of space and it's 80% full. I only need enough extra space to last until the end of the year. If I replace one of the 1TB drives with a 3TB drive, will I see an increase in available space? Or do I need to replace all of the drives?

    Eventually all the drives will be increased to 3TB drives, but ideally it could be one at a time.

    A new vdev isn't an option for me. I'm using all available sata connections on my motherboard and all the 3.5" bays in my case.

    Thanks!
  5. cyberjock Forum Guard Dog/Admin

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    cyberjock, Aug 10, 2012

    Review the powerpoint presentation in my sig. It will answer your question as well as a bunch of others you don't know you have!
  6. Fpmurphy New Member

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    Fpmurphy, Aug 10, 2012

    Thanks! I was just about to edit my post saying I found what I was looking for after stumbling upon your powerpoint.

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