SOLID STATE DRIVE (SSD)
A solid-state drive, sometimes called a solid-state disk or electronic disk, is a data storage device that uses integrated circuit assemblies as memory to store data persistently. SSD technology uses electronic interfaces compatible with traditional block I/O hard disk drives. SSDs do not employ any moving mechanical components, which distinguishes them from traditional magnetic disks such as hard disk drives (HDDs) or floppy disk, which are electromechanical devices containing spinning disks and movable read/write heads. Compared to electromechanical disks, SSDs are typically less susceptible to physical shock, are silent, have lower access time and latency, but are more expensive per unit of storage.
HARD DISK DRIVES (HDD)
A hard disk drive (HDD; also hard drive, hard disk, or disk drive) is a device for storing and retrieving digital information, primarily computer data. It consists of one or more rigid (hence "hard") rapidly rotating discs (often referred to as platters), coated with magnetic material and with magnetic heads arranged to write data to the surfaces and read it from them. Hard drives are classified as non-volatile, random access, digital, magnetic, data storage devices.
Comparison of SSD with HDD
- In 2011 SSDs were available in sizes up to 2TB, but less costly 64 to 256GB drives were more common.
- In 2011 HDDs of up to 4TB were available.
(2)Read/write performance symmetry
- Less expensive SSDs typically have write speeds significantly lower than their read speeds. Higher performing SSDs have similar read and write speeds.
- HDDs generally have slightly lower write speeds than their read speeds.
(3)Weight and size
- Solid state drives, essentially semiconductor memory devices mounted on a circuit board, are small and light in weight.
- HDDs are relatively large and heavy, 3.5" drives more so than 2.5" and 1.8".
- SSDs have no moving parts and therefore are silent.
- HDDs have moving parts (heads, actuator, and spindle motor) and make some sound; noise levels vary between models, but can be significant.
(5)Random access time
- SSDs are about 0.1 ms - many times faster than HDDs because data is accessed directly from the flash memory
- HDD ranges from 5–10 ms due to the need to move the heads and wait for the data to rotate under the read/write head
(6)Data transfer rate
- SSD technology can deliver rather consistent read/write speed, typically ranging from about 100MB/s to 500MB/s, depending on the model. When SSDs access individual smaller blocks, performance is reduced. In general, the speeds are continuously improving.
- Once the head is positioned, when reading or writing a continuous track, a HDD can transfer data at about 100MB/s. Data transfer rate depends upon rotational speed, which can range from 4,200 to 15,000 rpm.
- SSDs do not usually require any special cooling and can tolerate higher temperatures than HDDs.
- According to Seagate, ambient temperatures above 95°F (35°C) can shorten the life of a hard disk, and reliability will be compromised at drive temperatures above 55°C or 131°F. Fan cooling may be required if temperatures would otherwise exceed these values.
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