SSD Glossary

Following are several terms that are often used in the discussion about solid state drives (SSDs) and storage in general. For clarification or more information on terms and how they apply to the SSD, please post to our SSD Forum.

TERM	ACRONYM or ABBREVIATION DESCRIPTION	DEFINITION
Cache	See definition	A memory technique to store most frequently used computer programs and data in a way to maximize overall performance of an application. In most systems this cache memory is a high speed component that is volatile (losses the stored data when power is removed).
CPU	Central Processing Unit	The primary computing elements in a computer.
DDR RAM	Double Data Rate Random Access Memory	The type of main memory common in personal computers and servers. This memory is volatile (losses the stored data when power is removed).
ECC	Error Correction Code	A technique used to detect and correct errors in stored data.
eSATA	External Serial Advanced Technology (AT) Attachment	See SATA. This version of SATA has a more robust cable that includes shielding for radio frequency protection.
ExtremeFFS	A version on the SANDISK Fast File System	A improved version of the TrueFFS invented by MSystems which SANDISK eventually acquired.
FLASH	This is not an acronym. See definition.	A type of non-volatile computer storage that can be electrically erased and reprogrammed.
Gb	Gigabit	A gigabit is 1,000,000,000 bits or 1 billion bits
GB	Gigabyte	A gigabyte is 1,000,000,000 bytes or 1 billion bytes. A byte is generally defined as 8 bits.
IOPS	Input Output Operations per second	This is a common benchmark for computer storage performance, and in particular random access mass storage devices and systems.
Mb	Megabit	A megabit is 1,000,000 bits or 1 million bits
MB	Megabyte	A megabyte is 1,000,000 bits or 1 million bytes. A byte is generally defined as 8 bits.
MLC	Multi-level Cell	A memory element capable of storing more than a single bit of data. For FLASH memory, this provides higher data density in a component but this also increases the bit error rate forcing more sophisticated firmware techniques to be created to deal with the errors. The alternative is SLC.
mSATA	A version of SATA	A small form factor SATS device of approximately 30mm x 4.75mm x 50.95mm in size.
NAND	A FLASH technology (generally speaking)	The term NAND is actually "Not AND," a logic method that was used to create a flip flop. The NAND flip flop could hold one bit of information. NAND FLASH memory utilizes a dense array of NAND flip flops coupled with high capacitance gates to create an electrically erasable and reprogrammable solid state memory.
NCQ	Native Command Queuing	A technique to increase performance of mass storage devices by allowing the individual device to internally optimize the order in which received read and write commands are executed.
nm	Abbreviation of nanometer	In this context it is used as a integrated circuit technology representing the wavelength of the lithography used for critical layers. The 32nm process technology is the state of the art in 2010.
PCI	Peripheral Component Interconnect	A parallel computer bus standard developed by INTEL in 1990 and used extensively as a means to interface peripheral devices to a personal computer.
PCI Express	A modern version of PCI used in backplane. It is a serial bus rather than a parallel bus.	It is a point-to-point serial bus rather than a parallel bus.
RAID	Redundant array of independent Disks	A technology to improve both the data integrity and data throughput performance by using 2 or more independent mass storage devices.
Random Read	See definition	A benchmark method to measure the performance of a mass storage device or system by doing data access and read-out of a certain amount of data.
Random Write	See definition	A benchmark method to measure the performance of a mass storage device or system by doing data access and writing of a certain amount of data.
SAN	Storage Area Network	A technique used to connect remote mass storage devices or systems to servers in a way that makes the operating system think they are local devices.
SAS	Serial Attached SCSI	A serial bus implementation of SCSI.
SATA	Serial Advanced Technology (AT) Attachment	1.5 Gbits/sec serial implementation of the Parallel AT attachment standard. A 7-contact data cable and a 15 contact power cable.
SATA II	Serial Advanced Technology (AT) Attachment	3 Gbits/sec Standard of SATA
SCSI	Small Computer System Interface	A parallel mass storage interface standard that uses a common cable. Initially developed and introduced in the late 1980s.
Sequential Read	See definition	A benchmark method to measure the performance of a mass storage device or system by doing data access and read-out of a large amount of contiguous of data. Sometimes referred to as data streaming.
Sequential Write	See definition	A benchmark method to measure the performance of a mass storage device or system by doing data access and writing of a large amount of contiguous of data. Sometimes referred to as recording.
SLC		A memory element capable of storing a single bit of data. For FLASH memory, this provides lower data density in a component than MLC but it offers a low error.
SMART	Self-Monitoring, Analysis, and Reporting Technology	A monitoring system to detect and report on various indicators of reliability, in the hope of anticipating failures.
SSD	Solid State Drive	A data storage device that uses nonvolatile solid state memory. These devices typically emulate a hard disk drive.
TRIM	See definition	A computer command used by a SSD to inform it of data blocks in the SSD memory space that are no longer in use. This command allows the SSD controller to reorganize the memory space it is managing to allow any unused space to be optimally relocated. The TRIM command is intended to become part of the AT Attachment interface standard.
ZIF/LIF	Zero Insertion Force/Low Insertion Force	An electrical connection method where no force is used to mate the plug to the receptacle. For SSD, these are common for creating removable devices.

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