云硬盘的性能如何衡量？一般使用以下几个指标对存储设备的性能进行描述：
IOPS：每秒读/写次数，单位为次（计数）。存储设备的底层驱动类型决定了不同的 IOPS。
吞吐量：每秒的读写数据量，单位为MB/s。
时延：IO操作的发送时间到接收确认所经过的时间，单位为秒。
FIO是测试磁盘性能的一个非常好的工具，用来对硬件进行压力测试和验证。建议使用libaio的I/O引擎进行测试，请自行安装FIO和Libaio。
请特别注意：
1. 请不要在系统盘上进行 fio 测试，避免损坏系统重要文件
2. fio测试建议在空闲的、未保存重要数据的硬盘上进行，并在测试完后重新制作文件系统。请不要在业务数据硬盘上测试，避免底层文件系统元数据损坏导致数据损坏
2. 测试硬盘性能时，推荐直接测试裸盘（如 vdb）；测试文件系统性能时，推荐指定具体文件测试（如 /data/file）
安装libaio、fio
apt install -y libaio-dev
wget http://brick.kernel.dk/snaps/fio-2.1.7.tar.gz
./configure
make
make make install
不同场景的测试公式基本一致，只有3个参数（读写模式，iodepth，blocksize）的区别。下面举例说明使用block size为4k，iodepth为1来测试顺序读性能的命令。
4k随意读测试iops
命令如下：
fio --bs=4k --ioengine=libaio --iodepth=1 --direct=1 --rw=read --time_based --runtime=600 --refill_buffers --norandommap --randrepeat=0 --group_reporting --name=fio-read --size=50G --filename=/dev/vdb1
每个工作负载适合的最佳iodepth不同，具体取决于您的特定应用程序对于 IOPS 和延迟的敏感程度。
参数说明：
常见用例如下：
block=4k iodepth=1 随机读测试，能反映磁盘的时延性能；
block=128K iodepth=32 能反映峰值吞吐性能 ;
block=4k iodepth=32 能反映峰值IOPS性能。
下图为SSD云硬盘的测试性能截图：
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另一种简单的测试方法
4k随机读写iops测试、512k顺序读写吞吐量测试
利用配置文件，此处的fio.conf是自己编写的脚本文件
root@VM-0-12-ubuntu:/home/ubuntu# cat fio.conf
[global]
ioengine=libaio
iodepth=128
time_based
direct=1
thread=1
group_reporting
randrepeat=0
norandommap
numjobs=32
timeout=6000
runtime=120
# 4K随机读，IOPS
[randread-4k]
rw=randread
bs=4k
filename=/dev/vdb1 #注：/dev/vdb是目标测试磁盘的设备名称
rwmixread=100
stonewall
# 4K随机写，IOPS
[randwrite-4k]
rw=randwrite
bs=4k
filename=/dev/vdb1
stonewall
# 512K顺序读，吞吐
[read-512k]
rw=read
bs=512k
filename=/dev/vdb1
stonewall
# 512K顺序写，吞吐
[write-512k]
rw=write
bs=512k
filename=/dev/vdb1
stonewall
执行命令
root@VM-0-12-ubuntu:/home/ubuntu#fio fio.conf
结果如下：
randread-4k: (g=0): rw=randread, bs=4K-4K/4K-4K/4K-4K, ioengine=libaio, iodepth=128
...
randwrite-4k: (g=1): rw=randwrite, bs=4K-4K/4K-4K/4K-4K, ioengine=libaio, iodepth=128
...
read-512k: (g=2): rw=read, bs=512K-512K/512K-512K/512K-512K, ioengine=libaio, iodepth=128
...
write-512k: (g=3): rw=write, bs=512K-512K/512K-512K/512K-512K, ioengine=libaio, iodepth=128
...
fio-2.1.7
Starting 128 threads
randread-4k: (groupid=0, jobs=32): err= 0: pid=24060: Tue Apr 17 12:34:20 2018
read : io=960768KB, bw=8002.9KB/s, iops=2000, runt=120053msec
slat (usec): min=1, max=875635, avg=15984.07, stdev=68311.64
clat (msec): min=5, max=5043, avg=2019.68, stdev=397.04
lat (msec): min=40, max=5111, avg=2035.66, stdev=398.82
clat percentiles (msec):
| 1.00th=[ 1045], 5.00th=[ 1270], 10.00th=[ 1434], 20.00th=[ 1860],
| 30.00th=[ 1942], 40.00th=[ 1975], 50.00th=[ 2008], 60.00th=[ 2040],
| 70.00th=[ 2089], 80.00th=[ 2180], 90.00th=[ 2638], 95.00th=[ 2769],
| 99.00th=[ 2933], 99.50th=[ 2966], 99.90th=[ 3261], 99.95th=[ 4015],
| 99.99th=[ 5014]
bw (KB /s): min= 0, max= 894, per=3.14%, avg=251.18, stdev=128.48
lat (msec) : 10=0.01%, 20=0.01%, 50=0.02%, 100=0.01%, 250=0.01%
lat (msec) : 500=0.16%, 750=0.32%, 1000=0.32%, 2000=45.22%, >=2000=53.95%
cpu : usr=0.02%, sys=0.09%, ctx=209159, majf=0, minf=3128
IO depths : 1=0.1%, 2=0.1%, 4=0.1%, 8=0.1%, 16=0.2%, 32=0.4%, >=64=99.2%
submit : 0=0.0%, 4=100.0%, 8=0.0%, 16=0.0%, 32=0.0%, 64=0.0%, >=64=0.0%
complete : 0=0.0%, 4=100.0%, 8=0.0%, 16=0.0%, 32=0.0%, 64=0.0%, >=64=0.1%
issued : total=r=240192/w=0/d=0, short=r=0/w=0/d=0
latency : target=0, window=0, percentile=100.00%, depth=128
randwrite-4k: (groupid=1, jobs=32): err= 0: pid=24182: Tue Apr 17 12:34:20 2018
write: io=960800KB, bw=8002.2KB/s, iops=2000, runt=120068msec
slat (usec): min=2, max=884998, avg=15984.48, stdev=66543.07
clat (msec): min=4, max=7981, avg=2017.39, stdev=385.47
lat (msec): min=27, max=7981, avg=2033.37, stdev=387.03
clat percentiles (msec):
| 1.00th=[ 1057], 5.00th=[ 1319], 10.00th=[ 1467], 20.00th=[ 1860],
| 30.00th=[ 1926], 40.00th=[ 1975], 50.00th=[ 2008], 60.00th=[ 2057],
| 70.00th=[ 2114], 80.00th=[ 2180], 90.00th=[ 2606], 95.00th=[ 2704],
| 99.00th=[ 2868], 99.50th=[ 2933], 99.90th=[ 3228], 99.95th=[ 5473],
| 99.99th=[ 7111]
bw (KB /s): min= 0, max= 878, per=3.14%, avg=251.08, stdev=154.28
lat (msec) : 10=0.01%, 50=0.02%, 100=0.03%, 250=0.01%, 500=0.01%
lat (msec) : 750=0.42%, 1000=0.37%, 2000=46.44%, >=2000=52.72%
cpu : usr=0.02%, sys=0.10%, ctx=170362, majf=0, minf=32
IO depths : 1=0.1%, 2=0.1%, 4=0.1%, 8=0.1%, 16=0.2%, 32=0.4%, >=64=99.2%
submit : 0=0.0%, 4=100.0%, 8=0.0%, 16=0.0%, 32=0.0%, 64=0.0%, >=64=0.0%
complete : 0=0.0%, 4=100.0%, 8=0.0%, 16=0.0%, 32=0.0%, 64=0.0%, >=64=0.1%
issued : total=r=0/w=240200/d=0, short=r=0/w=0/d=0
latency : target=0, window=0, percentile=100.00%, depth=128
read-512k: (groupid=2, jobs=32): err= 0: pid=24304: Tue Apr 17 12:34:20 2018
read : io=15682MB, bw=133566KB/s, iops=260, runt=120224msec
slat (usec): min=31, max=2782.5K, avg=122435.74, stdev=251753.79
clat (msec): min=35, max=24997, avg=14629.26, stdev=3582.09
lat (msec): min=140, max=25077, avg=14751.70, stdev=3588.71
clat percentiles (msec):
| 1.00th=[ 1844], 5.00th=[ 6128], 10.00th=[10945], 20.00th=[13042],
| 30.00th=[14091], 40.00th=[14877], 50.00th=[15008], 60.00th=[15926],
| 70.00th=[16057], 80.00th=[16712], 90.00th=[16712], 95.00th=[16712],
| 99.00th=[16712], 99.50th=[16712], 99.90th=[16712], 99.95th=[16712],
| 99.99th=[16712]
bw (KB /s): min= 24, max=14278, per=3.11%, avg=4154.73, stdev=1645.11
lat (msec) : 50=0.01%, 100=0.01%, 250=0.09%, 1000=0.50%, 2000=0.82%
lat (msec) : >=2000=98.58%
cpu : usr=0.00%, sys=0.08%, ctx=27953, majf=0, minf=16899
IO depths : 1=0.1%, 2=0.2%, 4=0.4%, 8=0.8%, 16=1.6%, 32=3.3%, >=64=93.6%
submit : 0=0.0%, 4=100.0%, 8=0.0%, 16=0.0%, 32=0.0%, 64=0.0%, >=64=0.0%
complete : 0=0.0%, 4=99.9%, 8=0.0%, 16=0.0%, 32=0.0%, 64=0.0%, >=64=0.1%
issued : total=r=31363/w=0/d=0, short=r=0/w=0/d=0
latency : target=0, window=0, percentile=100.00%, depth=128
write-512k: (groupid=3, jobs=32): err= 0: pid=24426: Tue Apr 17 12:34:20 2018
write: io=16117MB, bw=137117KB/s, iops=267, runt=120359msec
slat (usec): min=39, max=3744.3K, avg=118989.73, stdev=211850.72
clat (msec): min=44, max=23277, avg=14163.52, stdev=3673.67
lat (msec): min=44, max=23978, avg=14282.51, stdev=3684.25
clat percentiles (msec):
| 1.00th=[ 1074], 5.00th=[ 5276], 10.00th=[10028], 20.00th=[12256],
| 30.00th=[13435], 40.00th=[14222], 50.00th=[15008], 60.00th=[15664],
| 70.00th=[16057], 80.00th=[16712], 90.00th=[16712], 95.00th=[16712],
| 99.00th=[16712], 99.50th=[16712], 99.90th=[16712], 99.95th=[16712],
| 99.99th=[16712]
bw (KB /s): min= 22, max=42965, per=3.21%, avg=4395.78, stdev=2482.81
lat (msec) : 50=0.02%, 250=0.19%, 500=0.20%, 750=0.06%, 1000=0.44%
lat (msec) : 2000=0.88%, >=2000=98.20%
cpu : usr=0.04%, sys=0.06%, ctx=29046, majf=0, minf=32
IO depths : 1=0.1%, 2=0.2%, 4=0.4%, 8=0.8%, 16=1.6%, 32=3.2%, >=64=93.7%
submit : 0=0.0%, 4=100.0%, 8=0.0%, 16=0.0%, 32=0.0%, 64=0.0%, >=64=0.0%
complete : 0=0.0%, 4=99.9%, 8=0.0%, 16=0.0%, 32=0.0%, 64=0.0%, >=64=0.1%
issued : total=r=0/w=32233/d=0, short=r=0/w=0/d=0
latency : target=0, window=0, percentile=100.00%, depth=128
Run status group 0 (all jobs):
READ: io=960768KB, aggrb=8002KB/s, minb=8002KB/s, maxb=8002KB/s, mint=120053msec, maxt=120053msec
Run status group 1 (all jobs):
WRITE: io=960800KB, aggrb=8002KB/s, minb=8002KB/s, maxb=8002KB/s, mint=120068msec, maxt=120068msec
Run status group 2 (all jobs):
READ: io=15682MB, aggrb=133566KB/s, minb=133566KB/s, maxb=133566KB/s, mint=120224msec, maxt=120224msec
Run status group 3 (all jobs):
WRITE: io=16117MB, aggrb=137117KB/s, minb=137117KB/s, maxb=137117KB/s, mint=120359msec, maxt=120359msec
Disk stats (read/write):
vdb: ios=271670/273456, merge=0/1084, ticks=30026240/30626672, in_queue=62613216, util=100.00%