paulao@sd-XXXXX:~$ sudo dd if=/dev/zero of=/root/output conv=fdatasync bs=384k count=1k; rm -f /root/output 16:
1024+0 records in
1024+0 records out
402653184 bytes (403 MB) copied, 1.74116 s, 231 MB/s

paulao@sd-XXXXX:~$ dd if=/dev/zero of=test bs=64k count=16k conv=fdatasync; unlink test
16384+0 records in
16384+0 records out
1073741824 bytes (1.1 GB) copied, 5.53976 s, 194 MB/s