Testing Lustre 2.10.7 against zfs 0.8.0-rc5
If the file system is stored in pools created under previous versions of zfs and the project quota feature has not yet been enabled on those pools, writes fail with -EOPNOTSUPP
Debug logs on the OST seem to indicate that the -EOPNOTSUPP is returned from osd_declare_attr_set(), which requires that if Lustre has been built with the ZFS project quota feature enabled, that the pool must have the feature enabled.
It's unclear why this is necessary. In addition, every user who upgrades from an earlier version of lustre will initially be in this state, where their zfs software supports project quotas, but the feature is not enabled on the pool. As long as they do not enable the feature on the pool, they can revert to the earlier zfs version if they encounter issues.