dd bs=1M count=1024 if=/dev/zero of=test conv=fdatasync 1024+0 records in 1024+0 records out 1073741824 bytes (1.1 GB) copied, 2.17496 s, 494 MB/s hdparm -tT /dev/xvda /dev/xvda: Timing cached reads: 18560 MB in 1.98 seconds = 9358.78 MB/sec Timing buffered disk reads: 2510 MB in 3.00 seconds = 836.61 MB/sec`