With regards to "File-based RAID offers the promise of having to do less work and avoiding RAIDing the empty space", there has been some work on improving perfo

With regards to "File-based RAID offers the promise of having to do less work and avoiding RAIDing the empty space", there has been some work on improving performance of ZFS scrub and re silver. In the original algorithm, it worked very well for mostly-empty disks as it only had to check written data. But mostly full disks had worse performance for scrub compared to traditional raid, as the data was checked in tree order. So there was a lot of seeks. At least that is my understanding. Anyways, see these talks from the ZFS Developer conference about how scrubbing has been improved: * 2016 - adding batching to resilvering to improve performance: https://openzfs.org/wiki/Scrub/Resilver_Performance https://openzfs.org/wiki/Scrub/Resilver_Performance * 2020 - for mirrors (not RAIDz), Sequential Reconstruction can further improve resilver speed: https://openzfs.org/wiki/OpenZFS_Developer_Summit_2020 https://openzfs.org/wiki/OpenZFS_Developer_Summit_2020