I want to know whether a disk is a solid-state drive or hard disk.

`lshw` is not installed. I do `yum install lshw` and it says there is no package named lshw. I do not know which version of <http://pkgs.repoforge.org/lshw/> is suitable for my CentOS.

I search the net and there is nothing that explain how to know whether a drive is SSD or HDD. Should I just format them first?

Result of `fdisk -l`:

```
Disk /dev/sda: 120.0 GB, 120034123776 bytes
255 heads, 63 sectors/track, 14593 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x00074f7d

   Device Boot      Start         End      Blocks   Id  System
/dev/sda1   *           1          14      103424   83  Linux
Partition 1 does not end on cylinder boundary.
/dev/sda2              14         536     4194304   82  Linux swap / Solaris
Partition 2 does not end on cylinder boundary.
/dev/sda3             536       14594   112921600   83  Linux

Disk /dev/sdc: 120.0 GB, 120034123776 bytes
255 heads, 63 sectors/track, 14593 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x00000000

Disk /dev/sdb: 128.0 GB, 128035676160 bytes
255 heads, 63 sectors/track, 15566 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x00000000

Disk /dev/sdd: 480.1 GB, 480103981056 bytes
255 heads, 63 sectors/track, 58369 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x00000000

```