What is solid-state storage and a solid-state drive (SSD)?

Solid-state storage (SSS) is a data storage method that uses solid-state memory, which consists of microchips with no moving parts to store data. Solid-state memory uses the ‘on’ or ‘off’ state of capacitors on a circuit board to write the ones and zeros of binary code. SSS may take various forms, such as a solid-state drive (SSD), solid-state card, or solid-state module. SSS interface options include SATA (Serial Advanced Technology Attachment), SAS (Serial Attached SCSI), Fiber Channel, or PCIe (Peripheral Component Interconnect Express).

SSDs are highly distinguished from the other main form of storage, hard disk drives (HDDs). Disk drives contain spinning disks and moving read/write heads. They use optical or magnetic media and they tend to be more volatile and breakable. SSDs by contrast, are damaged less often, quieter, and have lower latency and lower access time. SSDs can easily be swapped in where a HDD was used because the two drives use the same interface.

A majority of SSDs use flash memory, which is a non-volatile, rewritable memory. Non-volatile memory is used for long term storage because it can retain data without power. This memory type includes HDD memory as well. Flash memory is available as NAND (an electronic logic gate; stands for Negated AND), which is cheaper and more durable, or NOR (Negated OR) which is used for high-performance read operations.

DRAM (Dynamic Random Access Memory) is a form of volatile memory used by some SSDs, meaning it loses its data when power is not supplied. It allows extremely fast data access and is not used for long term storage. RAM stores each bit of data in a separate capacitor on each integrated circuit. DRAM refreshes capacitor charge periodically because real capacitors leak charge and eventually lose their information. RAM that does not refresh the capacitors is called static RAM (SRAM). DRAM has a structural simplicity that allows it to reach a higher data capacity.

SSDs have several additional advantages over HDDs. Since no disk spin-up is required, SSDs have a faster startup than HDDs. Random access is faster for a SSD because no “seeking” motion is required like it is for a disk. Typically, SSDs require less power consumption than HDDs. SSDs usually weigh less than HDDs, writing/erasing failures occur less frequently, and defragmenting is unnecessary. Lastly, SSDs are immune to magnets.

HDDs have advantages over SSDs as well. SSDs are more expensive and their capacity is significantly lower than disk capacity. This is due to the fact that disks use markers to indicate ones and zeros while SSDs have to compress the size of capacitors in order to get more capacity, and capacitors have a finite minimization.