Solid-state drive (SSD)

A solid-state drive (SSD), sometimes called a solid-state disk or electronic disk, is a data storage device that uses solid-state memory to store persistent data with the intention of providing access in the same manner of a traditional block i/o hard disk drive. SSDs are distinguished from traditional magnetic disks such as hard disk drives (HDDs) or floppy disk, which are electromechanical. SSDs use microchips that retain data in non-volatile memory chips and contain no moving parts. Compared to electromechanical HDDs, SSDs are typically less susceptible to physical shock, are silent, have lower access time and latency, but are more expensive per gigabyte (GB).

Most SSDs use NAND-based flash memory, which retains memory even without power. SSDs using volatile random-access memory (RAM) also exist for situations that require even faster access, but do not necessarily need data persistence after power loss, or use external power or batteries to maintain the data after power is removed.
In terms of its nature, the SSD can be classified into two types based on flash-based and DRAM (Dynamic Random Access Memory).

In the market today we met a lot of flash-based SSD technology, such as Flash Drive, Secure Digital (SD Card), Micro SD Card, Multi Media Card (MMC) and Compact Flash (CF). While the SSD with the physical size of conventional hard-disk, which measures 1.8 inches and 2.5 inches with a capacity of up to above 128 GB, since 2008 has been gaining popularity in the market along with a more affordable price.
Flash-based SSDs utilize small amounts of DRAM for cache used to store information about the placement of data blocks and wear leveling information (a technique to extend the life of the flash-based memory). While the high-performance SSDs typically also comes with temporary storage of electrical power (energy storage). This component is generally composed of a series capacitor or a battery that serves to move the data from the cache to the SSD flash memory when the computer is turned off / die suddenly (if based capacitors) or to store data temporarily in cache (if using batteries).
The data in the flash-based SSDs are typically stored in a memory cell on the chip. In this group there are two types of memory cells are commonly used, the type of MLC (Multi Level Cell) and SLC (Single Level Cell).
MLC type SSD is usually cheaper than SLC-based. This is due to the MLC store data of 3 bits or more per cell, whereas for SLC only 1 bit only, so the cost per giga byte it becomes lower.
While the SLC type SSD cost more, but this type has its own advantages when compared with the kinds of MLC, which is the data transfer speed is higher, lower power consumption and durability of the memory cell is longer. One cause of high prices of this SLC is a higher manufacturing cost per giga byte considering its SLC type SSD is only capable of storing data with smaller amounts per cell.
Sedangkan SSD berbasis DRAM memiliki kecepatan akses data yang sangat tinggi (umumnya kurang dari 1 mili detik). Perangkat ini biasanya dilengkapi dengan baterai internal dan sistem penyimpanan data cadangan untuk memastikan tetap adanya data dalam SSD saat komputer dimatikan atau mati mendadak. Dalam kondisi ini, baterai dalam SSD akan memasok daya bagi rangkaian sel untuk menyalin semua informasi dari DRAM ke perangkat penyimpanan cadangan. Saat komputer dinyalakan lagi, semua informasi ini akan dikembalikan lagi ke DRAM.