frozenset([DRBD_B_DISK_BARRIERS, DRBD_B_DISK_DRAIN]),
frozenset([DRBD_B_DISK_BARRIERS, DRBD_B_DISK_FLUSH]),
frozenset([DRBD_B_DISK_BARRIERS, DRBD_B_DISK_FLUSH, DRBD_B_DISK_DRAIN]),
frozenset([DRBD_B_DISK_BARRIERS, DRBD_B_DISK_DRAIN]),
frozenset([DRBD_B_DISK_BARRIERS, DRBD_B_DISK_FLUSH]),
frozenset([DRBD_B_DISK_BARRIERS, DRBD_B_DISK_FLUSH, DRBD_B_DISK_DRAIN]),