Introduction to solid-state drive (SSD)
solid-state drive (SSD) is a solid-state storage device that uses integrated circuit assemblies as memory to store data. SSD is also known as solid-state disk although SSDs do not have physical disks. Form-factors and protocols such as SATA and SAS of traditional hard disk drive (HDD) may be used by SSD, greatly simplifying usage of SSDs in computers. New form factors such as the M.2 form factor, and new I/O protocols such as NVM Express have been developed to address specific requirements of the Flash memory technology used in SSDs.
There are no moving mechanical components in SSD. This makes them different from conventional electromechanical drives such as hard disk drives (HDDs) or floppy disks, which contain movable read/write heads and spinning disks. SSDs are typically more resistant to physical shock, run silently, have quicker access time and lower latency compared to electromechanical devices. The price of SSDs has continued to decline over time but SSDs are in 2018 are still more expensive per unit of storage than HDDs and are expected to continue to be so into the next decade.
In 2017, most SSDs use 3D TLC NAND-based flash memory. It is a type of non-volatile memory that retains data even when power is lost. SSDs may be constructed from random-access memory (RAM) for applications requiring fast access but not necessarily data persistence after power loss. Batteries can be employed as integrated power sources in such devices to retain data for a certain amount of time after external power is lost.
SSDs store data in electrical charges, which slowly leak over time if left without power. This is the reason why SSDs are not suited for archival purposes as the worn out drives (that have exceeded their endurance rating) start to lose data typically after one (if stored at 30 °C) to two (at 25 °C) years in storage.
Hybrid drives or solid-state hybrid drives (SSHDs) contains a large hard disk drive and an SSD cache to improve performance of frequently accessed data. Apple’s Fusion Drive combines the features of SSDs and HDDs in the same unit can be seen as an example of hybrid drives.
Features of SSDs:
Faster Read/Write Speeds: SSDs offer significantly faster read and write speeds than traditional hard disk drives (HDDs), which use spinning disks and mechanical read/write heads. This translates into faster boot times, application loading times, and overall system performance.
Lower Power Consumption: SSDs consume less power than HDDs, making them ideal for use in laptops, tablets, and other mobile devices that rely on battery power.
No Moving Parts: Unlike HDDs, which have spinning disks and mechanical read/write heads, SSDs have no moving parts. This makes them more resistant to shock and vibration, and less prone to mechanical failure.
Higher Reliability: Because SSDs have no moving parts, they are generally more reliable than HDDs, which are subject to mechanical wear and tear. SSDs also have a lower rate of data loss due to read/write errors.
Lower Noise and Heat Output: SSDs generate less noise and heat than HDDs, making them ideal for use in quiet environments or systems with limited cooling.
Higher Cost per GB: SSDs are typically more expensive than HDDs on a cost-per-GB basis, although prices have come down in recent years. This makes SSDs less practical for use in systems that require large amounts of storage.
Limited Write Endurance: SSDs have a limited number of write cycles before the NAND-based flash memory cells degrade. However, modern SSDs use techniques such as wear leveling and overprovisioning to prolong the lifespan of the drive.
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