bart temp # dd if=/dev/zero of=file bs=1M count=2000
2000+0 records in
2000+0 records out
2097152000 bytes (2.1 GB) copied, 49.7258 s, 42.2 MB/s
bart temp # dd if=/dev/md0 of=/dev/null bs=1M count=2000
2000+0 records in
2000+0 records out
2097152000 bytes (2.1 GB) copied, 17.3082 s, 121 MB/s
bart temp # cat /proc/mdstat
Personalities : [linear] [raid0] [raid1] [raid10] [raid6] [raid5] [raid4]
md0 : active raid5 hdg1[2] hde1[1] hdc1[0]
      976767872 blocks level 5, 64k chunk, algorithm 2 [3/3] [UUU]

unused devices: <none>
bart temp # dd if=/dev/hdg of=/dev/null bs=1M count=2000 skip=3000
2000+0 records in
2000+0 records out
2097152000 bytes (2.1 GB) copied, 33.7468 s, 62.1 MB/s

##this drive is sata, seperate:
bart temp # dd if=/dev/zero of=/file bs=1M count=2000;rm /file
2000+0 records in
2000+0 records out
2097152000 bytes (2.1 GB) copied, 33.1092 s, 63.3 MB/s