[throw0101a]

> initial issues

You mean like the current advice not to use anything except mirroring and striping (RAID-0/1/10)?

> Parity may be inconsistent after a crash (the "write hole"). The problem born when after "an unclean shutdown" a disk failure happens. But these are two distinct failures. These together break the BTRFS raid5 redundancy. If you run a scrub process after "an unclean shutdown" (with no disk failure in between) those data which match their checksum can still be read out while the mismatched data are lost forever.

* https://btrfs.wiki.kernel.org/index.php/RAID56

I've been using ZFS since it came out on Solaris 10 over a decade ago and it was specifically designed not to have a write hole due to its COW/ACID nature.

See this 2008 SNIA presentation from Bonwick and Moore, the creators of ZFS talking about not having a write hole:

* ACID/COW: https://www.youtube.com/watch?v=NRoUC9P1PmA&t=24m

* Integrity: https://www.youtube.com/watch?v=NRoUC9P1PmA&t=55m20s