Solid-state drive
Organization or committee Subcommittee of : Purpose
INCITS N/A Coordinates technical standards activity between ANSI in the US and joint ISO/IEC committees worldwide
T10 INCITS SCSI
T11 INCITS FC
T13 INCITS ATA
JEDEC N/A Develops open standards and publications for the microelectronics industry
JC-64.8 JEDEC Focuses on solid-state drive standards and publications
NVMHCI N/A Provides standard software and hardware programming interfaces for nonvolatile memory subsystems
SATA-IO N/A Provides the industry with guidance and support for implementing the SATA specification
SFF Committee N/A Works on storage industry standards needing attention when not addressed by other standards committees
SNIA N/A Develops and promotes standards , technologies , and educational services in the management of information
SSSI SNIA Fosters the growth and success of solid state storage
Standardization organizations
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. It is also sometimes called a solid-state device or a solid-state disk, although SSDs lack the physical spinning disks and movable read-write heads used in hard drives (HDD) or floppy disks. Compared with the electromechanical drives, SSDs are typically more resistant to physical shock, run silently, and have quicker access time and lower latency. SSDs store data in semiconductor cells. As of 2019, cells can contain between 1 and 4 bits of data. SSD storage devices vary in their properties according to the number of bits stored in each cell, with single bit cells (SLC) being generally the most reliable, durable, fast, and expensive type, compared with 2 and 3 bit cells (MLC and TLC), and finally quad bit cells (QLC) being used for consumer devices that do not require such extreme properties and are the cheapest of the four. 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. Hybrid drives or solid-state hybrid drives (SSHDs), such as Apple's Fusion Drive, combine features of SSDs and HDDs in the same unit using both flash memory and a HDD in order to improve the performance of frequently-accessed data. While the price of SSDs has continued to decline over time, SSDs are () still more expensive per unit of storage than HDDs and are expected to remain so into the next decade. SSDs based on NAND Flash will slowly leak charge over time if left for long periods without power. This causes worn-out drives (that have exceeded their endurance rating) to start losing data typically after one year (if stored at 30 °C) to two years (at 25 °C) in storage; for new drives it takes longer. Therefore, SSDs are not suitable for archival storage.