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I am aware of course. I was explaining why adding a single drive does make sense for RAID10 just fine and, as an example, btrfs has it (existence proof), but Z

I am aware of course. I was explaining why adding a single drive does make sense for RAID10 just fine and, as an example, btrfs has it (existence proof), but ZFS doesn't support it. Your example doesn't expand the storage of the vdev, which is what this entire discussion is about, it merely adds a mirror.

zaarn 5y ago
You can definitely expand and shrink a zpool based on mirrors. You can remove top-level vdevs, provided the pool is fine, and expand existing pools by adding new mirrors.
- wtallis 5y ago
  Resizing a pool that uses mirrored vdevs isn't the question; resizing vdevs is.
  - NavinF 5y ago
    In what situation would increasing the size of a vdev be better than increasing the size of a pool? The submission increases the size of a raidz vdev and that's incredibly useful, but when would that make sense for a mirror?
    - wtallis 5y ago
      > In what situation would increasing the size of a vdev be better than increasing the size of a pool? When you want to add a single drive to expand your available storage capacity, without reducing the degree of redundancy you're already using. That use case should have been obvious given how much discussion it's already received in this thread, so I think you have some kind of blind spot about anything small-scale. This is why it's good to actually understand the competition, even after deciding which tradeoffs are right for you.
  - zaarn 5y ago
    You can now with this feature. If you're using RAID1 vdevs, you could always remove and add mirrors. Now you can at least add a device to a RAIDZn vdev.
    - wtallis 5y ago
      > If you're using RAID1 vdevs, you could always remove and add mirrors. This is still answering the wrong question, unless by "add mirrors" you mean "add another drive to a mirrored vdev and get more usable capacity", which I don't think is how ZFS works and would be strange to summarize as "add mirrors". I'm trying to discuss an idea you don't seem to have any terminology for. Can you please try to meet me halfway and at least respond in a manner that makes it clear you understand there's a real distinction to be made?
      - zaarn 5y ago
        You can add and removes devs from a vdev in ZFS now, with this feature, giving you the ability to resize a vdev. But only upwards. Downwards isn't possible yet.

zaarn 5y ago

You can definitely expand and shrink a zpool based on mirrors. You can remove top-level vdevs, provided the pool is fine, and expand existing pools by adding new mirrors.

wtallis 5y ago
Resizing a pool that uses mirrored vdevs isn't the question; resizing vdevs is.
- NavinF 5y ago
  In what situation would increasing the size of a vdev be better than increasing the size of a pool? The submission increases the size of a raidz vdev and that's incredibly useful, but when would that make sense for a mirror?
  - wtallis 5y ago
    > In what situation would increasing the size of a vdev be better than increasing the size of a pool? When you want to add a single drive to expand your available storage capacity, without reducing the degree of redundancy you're already using. That use case should have been obvious given how much discussion it's already received in this thread, so I think you have some kind of blind spot about anything small-scale. This is why it's good to actually understand the competition, even after deciding which tradeoffs are right for you.
- zaarn 5y ago
  You can now with this feature. If you're using RAID1 vdevs, you could always remove and add mirrors. Now you can at least add a device to a RAIDZn vdev.
  - wtallis 5y ago
    > If you're using RAID1 vdevs, you could always remove and add mirrors. This is still answering the wrong question, unless by "add mirrors" you mean "add another drive to a mirrored vdev and get more usable capacity", which I don't think is how ZFS works and would be strange to summarize as "add mirrors". I'm trying to discuss an idea you don't seem to have any terminology for. Can you please try to meet me halfway and at least respond in a manner that makes it clear you understand there's a real distinction to be made?
    - zaarn 5y ago
      You can add and removes devs from a vdev in ZFS now, with this feature, giving you the ability to resize a vdev. But only upwards. Downwards isn't possible yet.