It seems likely that this is a ZFS issue rather than specifically an LXD issue - the backing store I used for lxd was zfs, which is known not to support O_DIRECT.
I am re-testing this with directory backed lxd now.
It seems likely that this is a ZFS issue rather than specifically an LXD issue - the backing store I used for lxd was zfs, which is known not to support O_DIRECT.
I am re-testing this with directory backed lxd now.