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> and fixup the block pointers That's why. Due to reasons[1], ZFS does not have the capability to rewrite block pointers. It's been a long requested feature[2]

> and fixup the block pointers That's why. Due to reasons[1], ZFS does not have the capability to rewrite block pointers. It's been a long requested feature[2] as it would also allow for defragmentation. I've been thinking this could be solved using block pointer indirection, like virtual memory, at the cost of a bit of speed. But I'm by no means a ZFS developer, so there's surely something I'm missing. [1]: http://eworldproblems.mbaynton.com/posts/2014/zfs-block-pointer-rewrite-status-2013/index.html http://eworldproblems.mbaynton.com/posts/2014/zfs-block-poin... [2]: https://github.com/openzfs/zfs/issues/3582 https://github.com/openzfs/zfs/issues/3582

phongn 2y ago
It looks like they’re playing more with indirection features now (created for vdev removal) for other features. One of the recent summit hackathons sketched out using indirect vdevs to perform rebalancing. Once you get a lot of snapshots, though, the indirection costs start to rise.