参考链接： https://bbs.aliyun.com/read/112745.html
第一次访问文件平均读速度 534 MB/s
[root@spr TestHIRedis2]# time dd if=20160706.data of=/dev/null bs=8k
169781+1 records in
169781+1 records out
1390850376 bytes (1.4 GB) copied, 2.59958 s, 535 MB/s
real 0m2.601s
user 0m0.013s
sys 0m0.490s
[root@spr TestHIRedis2]# time dd if=20160707.data of=/dev/null bs=8k
146294+1 records in
146294+1 records out
1198446960 bytes (1.2 GB) copied, 2.66541 s, 450 MB/s
real 0m2.667s
user 0m0.015s
sys 0m0.428s
[root@spr TestHIRedis2]# time dd if=20160715.data of=/dev/null bs=8k
146157+1 records in
146157+1 records out
1197324960 bytes (1.2 GB) copied, 2.2439 s, 534 MB/s
real 0m2.245s
user 0m0.010s
sys 0m0.406s
[root@spr TestHIRedis2]# time dd if=20160718.data of=/dev/null bs=8k
149590+1 records in
149590+1 records out
1225446360 bytes (1.2 GB) copied, 2.29302 s, 534 MB/s
real 0m2.295s
user 0m0.016s
sys 0m0.516s
[root@spr TestHIRedis2]# time dd if=20160719.data of=/dev/null bs=8k
150542+1 records in
150542+1 records out
1233244872 bytes (1.2 GB) copied, 2.30762 s, 534 MB/s
real 0m2.309s
user 0m0.023s
sys 0m0.507s
第二次访问平均速度(Centos已经加载到缓存，实际上是内存读速度了)：4.1GB/s
[root@spr TestHIRedis2]# time dd if=20160719.data of=/dev/null bs=8k
150542+1 records in
150542+1 records out
1233244872 bytes (1.2 GB) copied, 0.302363 s, 4.1 GB/s
real 0m0.304s
user 0m0.015s
sys 0m0.289s
[root@spr TestHIRedis2]# time dd if=20160718.data of=/dev/null bs=8k
149590+1 records in
149590+1 records out
1225446360 bytes (1.2 GB) copied, 0.296327 s, 4.1 GB/s
real 0m0.298s
user 0m0.016s
sys 0m0.283s
[root@spr TestHIRedis2]# time dd if=20160715.data of=/dev/null bs=8k
146157+1 records in
146157+1 records out
1197324960 bytes (1.2 GB) copied, 0.293481 s, 4.1 GB/s
real 0m0.295s
user 0m0.010s
sys 0m0.285s
