SATA and SAS) and standard HDD form factors allow such SSDs to be used as drop-in replacements for HDDs in computers and other devices. SSDs can use traditional HDD interfaces and form factors, or newer interfaces and form factors that exploit specific advantages of the flash memory in SSDs. 3D XPoint is a possible exception to this rule it is a relatively new technology with unknown long-term data-retention characteristics Therefore, SSDs are not suitable for archival storage. This causes worn-out drives (that have exceeded their endurance rating) to start losing data typically after one year (if stored at 30 ☌) to two years (at 25 ☌) in storage for new drives it takes longer. SSDs based on NAND flash will slowly leak charge over time if left for long periods without power. Bcache achieves a similar effect purely in software, using combinations of dedicated regular SSDs and HDDs.
Hybrid drives or solid-state hybrid drives (SSHDs), such as Intel's Hystor and Apple's Fusion Drive, combine features of SSDs and HDDs in the same unit using both flash memory and spinning magnetic disks in order to improve the performance of frequently-accessed data. In addition, 3D XPoint memory (sold by Intel under the Optane brand) stores data by changing the electrical resistance of cells instead of storing electrical charges in cells, and SSDs made from RAM can be used for high speed, when data persistence after power loss is not required, or may use battery power to retain data when its usual power source is unavailable. SSD storage devices vary in their properties according to the number of bits stored in each cell, with single-bit cells ("Single Level Cells" or "SLC") being generally the most reliable, durable, fast, and expensive type, compared with 2- and 3-bit cells ("Multi-Level Cells/MLC" and "Triple-Level Cells/TLC"), and finally quad-bit cells ("QLC") being used for consumer devices that do not require such extreme properties and are the cheapest per gigabyte (GB) of the four. As of 2019, cells can contain between 1 and 4 bits of data. In comparison to hard disk drives and similar electromechanical media which use moving parts, SSDs are typically more resistant to physical shock, run silently, and have higher input/output rates and lower latency. SSD also has rich internal parallelism for data processing.
It is also sometimes called a semiconductor storage device, a solid-state device or a solid-state disk, even though SSDs lack the physical spinning disks and movable read–write heads used in hard disk drives (HDDs) and floppy disks.
A solid-state drive ( SSD) is a solid-state storage device that uses integrated circuit assemblies to store data persistently, typically using flash memory, and functioning as secondary storage in the hierarchy of computer storage.
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