Solid State Disk

What is Solid-State Hard Drive?

A solid-state hard drive (SSD) is a data storage device that uses solid-state memory to store persistent data. An SSD emulates a hard disk drive interface, thus easily replacing it in most applications. An SSD using SRAM or DRAM (instead of flash memory) is often called a RAM-drive, not to be confused with a RAM disk.

The original usage of the term solid-state (from solid-state physics) refers to the use of semiconductor devices rather than electron tubes, but in this context, has been adopted to distinguish solid-state electronics from electromechanical devices as well. With no moving parts, solid-state drives are less fragile than hard disks and are also silent (unless a cooling fan is used); as there are no mechanical delays, they usually enjoy low access time and latency.

Features

A solid-state hard drive (SSD) is a drive that has no moving parts and is therefore virtually silent in operation. SSDs can achieve this by using semiconductors to store memory instead of a magnetic surface like traditional hard drives. Although commonly recognizable as thumb drives or travel drives, there are also larger-capacity SSDs that can be used as main boot drives. Solid-state drives also allow for accelerated access to files and applications, allowing for increased overall performance for a computer.

Comparison to Hard Disk Drives

Hard disk drives (HDD) are bulkier and slower than SSDs. This is because the HDDs have moving parts that need to start spinning to access information. Although the time it takes for access may not be long at all, a SSD provides nearly instant data access. The time difference can be especially notable during startup.
Hard disk drives are more prone to failure than SSDs. Dust can get into the drive, or the spinning part can become faulty. Because SSDs can be designed to be airtight and because there are no moving parts, SSDs are not prone to these problems.
As of 2009, the cost of solid-state drives was high. HDDs with 10 times the capacity of solid-state drives could be purchased for a fraction of the cost.

Benefits to Laptops

One of the main benefits for SSDs is its application in laptops. The physical size of SSDs is smaller than HDDs. Also, the SSD’s faster memory access means faster overall performance. The result is a more portable, compact laptop that does not necessarily sacrifice performance.

Misconceptions

Because of the SSD’s nearly instant data access, there is a conception that the drive would cause the computer to be more efficient not only in terms of data access, but also in terms of energy consumption. Although the drive itself may be more efficient than a hard disk drive, the bottleneck that a computer experiences when pulling or writing to a HDD is removed with a SSD. The result is that the computer is able to process information quicker, causing other components such as the processor to be more active. Thus, although drive efficiency may improve in the future, in 2009, there is not a clear result as to whether the drives produce energy savings.

Speculation

Although in 2009 solid-state drives are expensive and limited by capacity, as with other drives, that will change. Hard disk drives used to be about $1 for every gigabyte of capacity. Currently, there are some 1 terabyte drives for less than $100. In the same way, as production costs drop and sales rise, the cost of a SSD will start to fall. Likewise, as manufacturers make better drives, capacity will increase. In the future, most computers may be using SSDs.

How Do Solid-State Hard Drives Work?

1. Unlike magnetic hard drives, solid state hard drives have no moving parts and do not rely on magnetic fields to store data. Because they use electrical current, rather than motors and magnets, to store data, they can access data noiselessly and with less power consumption. Solid state drives are also not subject to the same physical damage from impacts or large magnetic forces, making them suitable for mobile computers.
2. Solid state hard drives use a series of transistors, pieces of silicone and semiconductors to transfer the electrical current. Each piece is microscopic and can be affected by the transfer of a few electrons. Like all data storage, solid state drives use binary, a series of 1s and 0s, to represent data. A 0 is represented by a transistor that cannot accept an electrical current, while a 1 is represented by one that allows the flow of electricity.
3. A blank drive, or a blank section of the drive, is denoted by all 1s. All transistors in this section will allow the free flow of current. When data is recorded, voltage is applied to one piece of silicone, known as the control gate. This process transfers electrons to another piece, the floating gate. When the floating gate is filled with electrons, current will not pass through it and the drive reads it as a 0.
4. As you write or delete data from the drive, the information is converted by the program to binary data. This is sent to the drive’s writing center, where it is converted to electrical currents and used to realign the transistors. To read data, the read center of the drive sends a current through the portion that holds the data to be read and returns the sequence of 1s and 0s. This sequence is sent to the program and presented as information you can read.
5. The writing process of solid state drives offers several benefits, such as the ability to use the drive while in motion, but the technology is subject to limitations. Most notably, each transistor can only be written to a certain number of times before it will no longer function. Each drive employs advanced methods, known as wear leveling, to prevent a particular section of the drive from premature wear. Even with wear leveling, solid state drives eventually need to be replaced as sections become unwritable.