Solid State Disk is also called Solid State Drive (SDD for short). Actually, it is an
application of FLSH. If you uncover the housing of SSD, you will find a circuit board
composed of flash IC chips. As there is no driving motor or disk structure of traditional
disk, SSD has no problem similar to that of traditional disk.

In early stage, SSD was used in the fields of military and space. These industries have
very strict requirement in respect of hardware storage device and its solidity. As the price
of NAND Flash was falling in recent years, and cost per unit was reduced correspondingly,
it is gradually used in the field of industrial computer instead of traditional disk.

We try to make simply analogy by use of computer. Memories used by general
computer are divided into dynamic memory and solid state memory. Disk is solid
state memory. Once date is stored in the disk, data is memorized in the disk.
Dynamic disk is the RAM, which is the element the shop clerks often ask us to
buy additional 1G when we buy computer. When computer execute software
program, the software will catch the memory of RAM as it operation buffer space.
When the software is closed, dynamic memory will release data and dynamic
memory will be cleaned, waiting for use of next software.

Traditional solid state memory is a hard disk. It has one disk and one reading
head. So when computer is reading, you cannot move it. A small disk contains
300G data, which is then read by the head. The vital flaws of such a precise
device are easy to be damaged, nondurable of dropping, nondurable of
vibration, and easy to be down. Purchase of disk is easy and is inexpensive,
but data store in the disk is very important. Changing a disk cost you only
several thousand dollars, but recovery of data is expensive.

We have ever heard the disk is damaged, but we rarely hear that RAM is
damaged, because RAM is made of transistors, and the chance of damage
to RAM is low. The disk made of transistors is SSD. Flash of SSD is made
of all transistors, simply saying.