硬盘读取速度测试

# 写
sync; dd if=/dev/zero of=/tmp/tempfile bs=1M count=1024; sync
1024+0 records in
1024+0 records out
1073741824 bytes (1.1 GB, 1.0 GiB) copied, 2.55331 s, 421 MB/s

# 读
dd if=/tmp/tempfile of=/dev/null bs=1M count=1024
1024+0 records in
1024+0 records out
1073741824 bytes (1.1 GB, 1.0 GiB) copied, 0.271083 s, 4.0 GB/s

# 清空cache，准确的测试真实的读速度：
sudo /sbin/sysctl -w vm.drop_caches=3
dd if=/tmp/tempfile of=/dev/null bs=1M count=1024