ZFS is designed to be a POSIX compliant file system and in most situations, ZFS is POSIX compliant. However, two edge case conditions exist when ZFS does not meet the POSIX compliance tests:
Updating ZFS files system capacity statistics.
Modifying existing data with a 100 percent full file system.
Related CRs:
6362314
6362156
6361650
6343113
6343039
6742203