Quick ZFS refresher

Discussion in 'Linux Admins, Storage and Virtualization' started by gigatexal, Nov 28, 2018.

  1. gigatexal

    gigatexal I'm here to learn

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    if I pick up and shuck three 8TB hard drives and maybe three more later what raidz levels should I use to be able to expand but also have the best parity and space.
     
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  2. MiniKnight

    MiniKnight Well-Known Member

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    I guess you're using RAID-Z which you can think of as RAID 5.
     
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  3. Jannis Jacobsen

    Jannis Jacobsen Active Member

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    hmm, 3 drives would likely be raidz.
    then you might be able to convert to 3 mirror vdevs an a pool, if you add 3 more drives.
    kinda like raid10, for performance and fault tolerance

    or 6 drives in raidz-2, for more storage, but less performance and redundancy.

    -j
     
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  4. gigatexal

    gigatexal I'm here to learn

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    If I start out with a raidz2 setup and 5 disks would I need to add another 5 to grow it? Or raidz1 with 3 disks and then just add the other 3 when I want to grow it to have some good amount of safety and then add a drive as a hot spare? I think I could do that: 7 drives 6 data and parity and 1 hot spare.
     
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  5. gigatexal

    gigatexal I'm here to learn

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    This whole strict balancing limitation is tough. I hope they add a more flexible way to do this even though it’s only really beneficial to us home users.
     
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  6. ttabbal

    ttabbal Active Member

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    The rule with ZFS is you need to add groups. You can't add a single drive and re-stripe an existing raidz. So if you want to expand a raidz, you need to add another raidz. It doesn't have to be identical, but it can make some things easier and performance is probably slightly better if you do.

    This is why I switched from 2xraidz2 to mirrors. I can upgrade or add 2 at a time, performance and rebuild speed are much better as well. Downside, more drives are needed. But I ended up getting a 24 disk supermicro case, so it's not an issue for me. And I got a deal on a bunch of 2TB drives, so a few pairs got added and I have a cold spare tested ready to go. I did have one drive start going, but of course it was a 4TB. Figures. :)
     
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  7. markarr

    markarr Active Member

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    What are you storing, is it mostly static or fluid? If its static say, media then you may want to explore something like snapraid where you can add and remove disks as you want, you can have 1 to 6 parity disk. Its snapshot based so any data that is changed between snapshots will be lost, so if you need realtime protection then it is not the solution for you.
     
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  8. gigatexal

    gigatexal I'm here to learn

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    That is the practical approach. Debating on building a setup to serve as a datastore for my Plex media and also as one for other things like VMs and source control etc. in the latter case dedup and compression would come in handy.

    You can get external 8TB drives for 140 or less. That’s what sparked all of this.
     
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  9. StammesOpfer

    StammesOpfer Active Member

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    Yeah I would think something like unraid for your media and maybe ZFS for your VMs and code. Though depending on your needs you could also just throw a few SSDs as separate devices in an unraid setup and probably have enough performance for whatever VMs you are trying to run. I wish they had proper r/w caching but it all depends on your performance needs.
     
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  10. markarr

    markarr Active Member

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    That's what i ended up doing. I have a proxmox host with zfs root drive for vms and docker containers, and then have dual parity snapraid and mergefs managing the 14 3tb drives for the plex/kodi media library.
     
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