$ for i in {10,100,1000,10000,100000,1000000}; do dd if=/dev/zero of=test.txt bs=4096 count=${i}; done
10+0 records in
10+0 records out
40960 bytes (41 kB) copied, 0.000618855 s, 66.2 MB/s
100+0 records in
100+0 records out
409600 bytes (410 kB) copied, 0.00102354 s, 400 MB/s
1000+0 records in
1000+0 records out
4096000 bytes (4.1 MB) copied, 0.00584651 s, 701 MB/s
10000+0 records in
10000+0 records out
40960000 bytes (41 MB) copied, 0.0549857 s, 745 MB/s
100000+0 records in
100000+0 records out
409600000 bytes (410 MB) copied, 3.59107 s, 114 MB/s
1000000+0 records in
1000000+0 records out
4096000000 bytes (4.1 GB) copied, 39.3971 s, 104 MB/s