[root@localhost data]# dd if=/dev/zero of=test1m.log bs=10M count=2000
2000+0 records in
2000+0 records out
20971520000 bytes (21 GB) copied, 126.633 s, 166 MB/s
[root@localhost data]# dd if=/dev/zero of=test1m.log bs=1M count=4000
4000+0 records in
4000+0 records out
4194304000 bytes (4.2 GB) copied, 40.6719 s, 103 MB/s
[root@localhost data]# dd if=/dev/zero of=test1m.log bs=10K count=4000
4000+0 records in
4000+0 records out
40960000 bytes (41 MB) copied, 0.0594011 s, 690 MB/s
[root@localhost data]# dd if=/dev/zero of=test1m.log bs=100K count=80000
80000+0 records in
80000+0 records out
8192000000 bytes (8.2 GB) copied, 78.821 s, 104 MB/s
[root@localhost data]# dd if=/dev/zero of=test1m.log bs=10K count=40000
40000+0 records in
40000+0 records out
409600000 bytes (410 MB) copied, 3.01761 s, 136 MB/s
[root@localhost data]# dd if=/dev/zero of=test1m.log bs=100K count=40000
40000+0 records in
40000+0 records out
4096000000 bytes (4.1 GB) copied, 39.6952 s, 103 MB/s[root@localhost data]# dd if=test1m.log of=/dev/null bs=100K count=40000
40000+0 records in
40000+0 records out
4096000000 bytes (4.1 GB) copied, 0.770792 s, 5.3 GB/s
[root@localhost data]# dd if=test1m.log of=/dev/null bs=1M count=40000
3906+1 records in
3906+1 records out
4096000000 bytes (4.1 GB) copied, 0.65342 s, 6.3 GB/s
[root@localhost data]# dd if=test1m.log of=/dev/null bs=10M count=40000
390+1 records in
390+1 records out
4096000000 bytes (4.1 GB) copied, 0.672658 s, 6.1 GB/s
[root@localhost data]# dd if=/dev/zero of=test1m.log bs=10M count=800
800+0 records in
800+0 records out
8388608000 bytes (8.4 GB) copied, 80.6793 s, 104 MB/s
[root@localhost data]# dd if=test1m.log of=/dev/null bs=1M count=4000
4000+0 records in
4000+0 records out
4194304000 bytes (4.2 GB) copied, 0.838768 s, 5.0 GB/s
[root@localhost data]# dd if=test1m.log of=/dev/null bs=10k count=40000
40000+0 records in
40000+0 records out
409600000 bytes (410 MB) copied, 0.206384 s, 2.0 GB/s
[root@localhost data]# dd if=test1m.log of=/dev/null bs=1k count=400000
400000+0 records in
400000+0 records out
409600000 bytes (410 MB) copied, 0.961552 s, 426 MB/s
[root@localhost data]#