1. 什么是HDDs

HDDs have been around over 60 years since IBM introduced them in 1956. The first disk drive was the size of a car, stored a mere 3.75 megabytes, and cost $300,000 in today’s dollars.自IBM于1956年推出硬盘驱动器以来，硬盘驱动器已经存在了60多年。第一个磁盘驱动器的大小与汽车相当，仅存储3.75兆字节，今天的成本为30万美元。

IBM 350 Disk Storage System — 3.75MB in 1956

2. 什么是SSDs

SSDs go back almost as far as HDDs, with the first semiconductor storage device compatible with a hard drive interface introduced in 1978, the StorageTek 4305.

固态硬盘几乎与硬盘驱动器一样，第一个半导体存储设备与1978年推出的硬盘驱动器接口兼容，即StorageTek 4305

Storage Technology 4305 SSD — 45MB in 1978

SSD circuit board

a. 通过检查是否支持旋转判断

cat  /sys/block/dm-0/queue/rotational

如果返回0表示是SSD硬盘，如果是1表示HDD硬盘

b. 通过lsblk 命令查找，该命令位于util-linux包

[root@k8s-uat-test-node01 ~]# lsblk -o NAME,MOUNTPOINT,MODEL,ROTA

NAME               MOUNTPOINT MODEL            ROTA

sr0                           QEMU DVD-ROM        1

vda                                               1

├─vda1             /boot                          1

└─vda2                                            1

├─centos-root    /                              1

├─centos-swap                                   1

└─centos-service /service                       1

c. 通过smartctl命令查找

smartctl -a /dev/sdb

如果有Rotation Rate:    Solid State Device 信息显示说明是SSD

https://unix.stackexchange.com/questions/65595/how-to-know-if-a-disk-is-an-ssd-or-an-hdd

d. 认识磁盘io

[root@k8s-uat-test-node01 ~]# cat /proc/diskstats

252       0 vda 84494184 201007 10734352824 15102148 1974560 273246 107437596 7484717 0 3615765 16077475

252       1 vda1 2007 0 52412 941 107 3 31355 676 0 955 1338

252       2 vda2 84492088 201007 10734295004 15101164 1607040 273243 107406241 7244181 0 3646663 16439879

11       0 sr0 18 0 2056 94 0 0 0 0 0 81 94

253       0 dm-0 83039947 0 9722932166 14647652 1270507 0 52492890 5951809 0 4103211 20685192

253       1 dm-1 88 0 4656 13 0 0 0 0 0 13 13

253       2 dm-2 2681466 0 1011356006 855384 616464 0 54913351 6430878 0 783796 7307385

https://www.kernel.org/doc/Documentation/iostats.txt

http://linuxperf.com/?p=156