sudo modprobe loop
	for i in 1 2 3 4; do
		dd if=/dev/zero of=${WORK_DIR}/disks/img.${i} bs=1M count=2000
		device=$(sudo losetup --find --show ${WORK_DIR}/disks/img.${i})
		sudo mkfs.ext4 -F ${device}
		mkdir -p ${WORK_DIR}/mnt/disk${i}/
		sudo mount ${device} ${WORK_DIR}/mnt/disk${i}/
		sudo chown "$(id -u):$(id -g)" ${device} ${WORK_DIR}/mnt/disk${i}/
	done
	set +e
}

**In our tests we also found ext4 does not honor POSIX O_DIRECT/Fdatasync semantics, ext4 trades performance for consistency guarantees. Please avoid ext4 in your setup.**