Solid State Drive       A solid state drive (SSD) is a data storage device that uses solid-state memory to store persistent data. An SSD emulates a hard disk drive, thus easily replacing it in any application. An SSD using SRAM or DRAM (instead of flash memory) is often called RAM-drive.       The original usage of the term solid state (from solid state physics) refers to the use of semiconductor devices rather than electron tubes, but has in this context been adopted to distinguish solid-state electronics from electromechanical devices as well. With no moving parts, a solid state drive is usually more robust, effectively eliminating the risk of mechanical failure, usually silent, and usually enjoys reduced seek time and latency by removing mechanical delays associated with hard disk drives.       Compared with hard disk drives   Advantages   Faster startup - as no spin-up is required. Typically near-instantaneous random access - since there is no read/write head to move. Extremely low read and write latency times - SSDs seek times are orders of magnitude smaller than the best current hard disk drives. Faster boot and application launch time - provided hard disk seeks are the limiting factor, see Amdahl's law. Lower power consumption and heat production - at least for small SSDs. High-end SSDs and SSDs larger than 64GB may have a much higher power consumption. No noise - Lack of moving parts makes the SSD completely silent, although high-end SSDs and large SSDs may include cooling fans. High mechanical reliability - Lack of moving parts almost eliminates the risk of mechanical failure. Better able to endure extreme shock, high altitude, vibration and temperatures - SSDs are tougher than traditional hard drivesThese features are useful for laptops, mobile computers, and devices that operate in extreme conditions. Relatively deterministic performance[3] - unlike hard disk drives, performance of SSDs is almost constant and deterministic across the entire storage. This is because seek time can be constant, so file fragmentation has less impact on performance than on disk drives. For low-capacity SSDs, lower weight and size - size and weight per unit storage are still better for traditional hard drives, and microdrives allow up to 20 GB storage in a CompactFlash 42.8×36.4×5 mm (1.7×1.4×.2 in) form factor. Up to 64GB, SSDs are lighter than hard drives for the same size.           source : http://www.wikipedia.org