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Definition: SSD

(Solid State Drive) An all-electronic, non-volatile random access storage drive. SSDs are the internal storage in smartphones, tablets and laptop computers and are increasingly used instead of hard drives in desktop computers. Emerging in the late 1990s, SSDs are faster than hard drives because there is no moving read/write head (zero latency). Without SSDs, smartphones and tablets would never have flourished. As of 2022, there are more than 50 manufacturers of SSDs. They use the SATA or NVMe interface and range from 128GB to 16TB; however, the largest SSD is Seagate's 60TB drive, which uses the SAS interface (see serial attached SCSI). See SATA and NVMe.

Comprising NAND flash memory chips, SSDs are available in multi-terabyte capacities. Although more expensive than hard disks, they are generally more reliable and offer greater protection in hostile environments. In addition, SSDs use less power and are not affected by magnets. See flash memory.

In time, there may only be solid state storage, and spinning disk platters will be as obsolete as the punch card. However, that may take another 30 years. See disk on module and garbage collection.

A Lot More Complex Than Hard Drives
Because flash memory eventually does wear out, SSDs distribute the writes evenly to all the sectors. A great amount of storage management takes place within the drive itself to ensure that sectors are not erased and written too many times.

Hybrid Drive (SSD and Disk)
Hybrid drives, such as the Fusion Drive in Macs, combine an SSD with a hard disk (see solid state hybrid drive and Fusion Drive).

Hard Drive Replacement Kits
This Kingston kit includes everything necessary to replace a desktop computer's hard drive with an SSD. Kits for laptops include an external case for the old drive while it is being cloned to the SSD. (Image courtesy of Kingston Technology Corporation, www.kingston.com)

Less Costly Every Year
In 2014, a 3TB hard drive (top) was a third the price of a 500GB SSD (bottom). However, by 2020, the same 500GB SSD cost less than $100. (Images courtesy of Micro Center, www.microcenter.com)

Early Fast Storage
These older devices used volatile RAM for very fast storage (no disk latency). In case of power failure, batteries in the MegaRAM (top) enabled the RAM's contents to be copied to the built-in hard disk. In 2001, 1GB MegaRAMs sold for $25,000. The i-RAM from Gigabyte (bottom) was released in 2005, and its battery kept up to 8GB of RAM current for several hours. See nvSRAM and BBSRAM. (Image courtesy of Imperial Technology, Inc.)

The First SSD
In 1977, this Dataram module tied eight magnetic core circuit boards together to make the first solid state disk. It held a whopping two megabytes. See core storage. (Image courtesy of Dataram Corporation, www.dataram.com)

Early SSDs on PC Cards
Minuscule by today's standards (capacities shown are in megabytes), these FLASHDISKs added storage to early laptops. Shown here with a CompactFlash card (upper left) for size comparison, they plugged into a PCMCIA slot (see PC Card). (Image courtesy of SanDisk Corporation, www.sandisk.com)

No, They're Not Dead
Since the late 1990s, SSDs were predicted to make hard drives obsolete. More than two decades later, disks are still thriving, and their capacities are getting larger all the time. See hard disk.