btrfs looks really interesting. And it's good to have an alternative to zfs, but for me, it's not yet ready for prime time. If you have a serious amount of data that you care about, mirroring and raid1 are jokes. (See https://jro.io/r2c2/ for comparisons of what various raid levels do for you.) With disks the size they are these days, you have a fair chance of another disk failing while you're re-building the checksums from a failed disk, and if you get read errors during the process, you'll never know. So raidZ2 (what btrfs calls raid5) is a minimum. (Note that this is a particular problem if you bought a bunch of the same disks (because they were a great deal) manufactured near the same time. We have noticed contemporaneous failures!) btrfs raid5/6 have some serious issues - a search following one of the links in the wikipedia article to: https://lore.kernel.org/linux-btrfs/20200627030614.GW10769@hungrycats.org/ and putting "raid5" in the search turns up numerous issues from the last couple of months; the SUSE support page describes a lot of (to me) very scary errors. So I'll stick with ZFS, particularly as the license issue seems to be "ancient" history. ../Dave