root@odroidhc2-1:/srv/dev-disk-by-label-wd1TBblack# sync;time dd if=/dev/zero of=test bs=16M count=256 oflag=direct
256+0 records in
256+0 records out
4294967296 bytes (4.3 GB, 4.0 GiB) copied, 46.1591 s, 93.0 MB/s

real    0m46.167s
user    0m0.000s
sys     0m12.905s
root@odroidhc2-1:/srv/dev-disk-by-label-wd1TBblack# sync;time dd if=/dev/zero of=test bs=128K count=32768 oflag=direct
32768+0 records in
32768+0 records out
4294967296 bytes (4.3 GB, 4.0 GiB) copied, 41.9339 s, 102 MB/s

real    0m42.014s
user    0m0.040s
sys     0m15.505s
root@odroidhc2-1:/srv/dev-disk-by-label-wd1TBblack# sync;time dd if=/dev/zero of=test bs=4096 count=1048576 oflag=direct
1048576+0 records in
1048576+0 records out
4294967296 bytes (4.3 GB, 4.0 GiB) copied, 388.068 s, 11.1 MB/s

real    6m29.128s
user    0m0.605s
sys     2m8.225s