SNIA Online Dictionary

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M.2	[Hardware] A card form factor and connector interface defined by the PCI-SIG that is most commonly used for solid state storage. M.2 interfaces to PCI Express, SATA-IO, and USB.
MAC	[Network], [Data Security] 1. Acronym for Media Access Control. 2. Acronym for Message Authentication Code. 3. Acronym for Mandatory Access Control.
magnetic remanence	[Data Security] Residual magnetic information remaining on a magnetic medium after the medium has been degaussed.
malware	[Computer System], [Data Security] Malicious software designed specifically to damage or disrupt a system, attacking confidentiality, integrity and/or availability. [ISO/IEC 27033-1] Examples are a computer virus, computer worm, Trojan horse, spyware, adware, ransomware, or scareware.
MAM	[Storage System] Acronym for Medium Auxiliary Memory.
MAMR	[Hardware] Acronym for microwave-assisted magnetic recording.
MAN	[Network] Acronym for Metropolitan Area Network.
Managed Object Format	[Management] The syntax and formal description of the classes and associations in a CIM schema. Managed Object Format (MOF) can be translated to XML using a Document Type definition published by the DMTF.
Management Component Transport Protocol	A DMTF-defined protocol that supports management communication between internal hardware components. MCTP is carried over an underlying bus (e.g., SMBus/I2C, serial links, PCI Express, or USB).
management framework	[Management] A structure and set of services exposed for use by management applications and other services in the management environment.
Management Information Base	[Management] The specification and formal description of a set of objects and variables that can be read and possibly written using the SNMP protocol. Various standard Management Information Bases (MIBs) are defined by the IETF and other standards bodies. Vendors define vendor-specific MIBs.
mandatory	[Standards] A provision in a standard that must be supported in order for an implementation of the standard to be compliant with the standard.
Mandatory Access Control	[Data Security] A type of access control based on the security clearance of the subject and the classification of the object. The control is mandatory in that a subject is not allowed to change either their security clearance or the classification of an object.
map	[General] The relationship between two or more items. For example, the relationship of virtual memory addresses to a portion of a file (e.g., POSIX).
mapping	[General] The establishment of a relationship between two or more items. An example is the establishment of a relationship between physical disk block addresses and the block addresses of the virtual disks presented to operating environments.
maximum time to first data	[Storage System] The maximum time required to start receiving data from a storage system to satisfy a read request for data.
maximum transfer unit	[Network] The largest amount of data that it is permissible to transmit as one unit according to a protocol specification.
MaxTTFD	[Storage System] Shorthand for maximum time to first data.
Mb / Mbit	[Computer System] Abbreviations for Megabit.
MB / MByte	[Computer System] Shorthand for megabyte.
Mbps	[Computer System] Megabits per second. A measure of data transfer rate.
MCTP	[Management] Acronym for Management Component Transport Protocol
MD5	[Data Security] Acronym for Message Digest 5.
mean time between failures	[General] The average time between consecutive failures of a system or component.
Mean Time To	[General] The average time from start of use to first failure in a large population of identical systems, components, or devices.
mean time to data	[Storage System] The average time required to stage a data stream from storage and make it available for reading by a client.
mean time to data loss	[Storage System] The average time, in a large population of storage elements, from first use until a failure results in a permanent loss of user data.
mean time to failure	[General] The average time from start of use to first failure in a large population of identical systems, components, or devices.
mean time to loss of data availability	[Storage System] The average time, in a large population of storage elements, from first use until a failure results in a loss of timely user data access. Loss of availability does not mean loss of data; data remains intact.
mean time to repair	[General] The average time, in a large population of identical systems, components, or devices, between a failure and completion of repair. Mean time to repair (MTTR) comprises all elements of repair time, from the occurrence of the failure to restoration of complete functionality. This includes time to notice and respond to the failure, time to repair or replace the failed component, and time to make the replaced component fully operational.
meaningful	[Standards] In a standard, a control field or bit that must be correctly interpreted by a receiver. Control fields are either meaningful or "not meaningful." In the latter case they must be ignored.
meaningful control field	[Standards] In a standard, a control field or bit that must be interpreted. Control fields are either meaningful or "not meaningful." In the latter case they must be ignored.
measured service	[Services] Metered dispensation of resources appropriate to a given type of service. Usage can be monitored, controlled, reported and billed. Examples include storage, processing, data transfer rate, and active user accounts.
mebibit	[General] Shorthand for 1,048,576 (220) bits. See also Megabit.
mebibyte	[General] Shorthand for 1,048,576 (220) bytes. See also megabyte.
media	[Network], [Storage System] 1. [Storage System] Synonym for storage media. 2. [Network] A physical link on which data is transmitted between two points.
media access control	[Network] 1. Algorithms that control access to physical media. 2. The media access control (MAC) layer in the Ethernet protocol.
media changer	[Storage] Deprecated term for library.
media ID	[Data Recovery] A machine-readable identifier written on a storage volume that remains constant throughout the volume's life. See external volume serial number, label.
media manager	[Storage System] A software component responsible for tracking the location, contents, and state of removable storage volumes.
media robot	[Storage System] Synonym for robotic media handler.
media sanitization	[Data Security] A general term referring to the actions taken to render data written on media unrecoverable by both ordinary and extraordinary means. [NIST SP 800-88]
medium	[Network], [Storage System] Synonym for media.
Medium Auxiliary Memory	[Storage System] A non-volatile memory, other than the recording medium, residing in a storage element (e.g., a tape cartridge) that is accessible to the storage device.
medium transport element	[SCSI] Synonym for robotic media handler.
megabaud	[Data Communication] One million baud.
megabit	[Computer System] 1,000,000 (106) bits. See also Mebibit.
megabyte	[Computer System] 1,000,000 (106) bytes. See also mebibyte.
megatransfer	[SCSI] The transfer of one million data units per second. The term is used to describe the characteristics of parallel I/O interconnects like SCSI, for which the data transfer rate depends upon the amount of data transferred in each data cycle.
melting	[Data Security] A method of sanitization that uses extreme heat to cause a device or component to change state, from solid to liquid and/or gas, in an approved facility. [ISO/IEC 27040]
member disk	[Storage System] A disk used as a member of a disk array.
memory cell	[Hardware] The smallest physical storage entity within storage.
Message Authentication Code	[Data Security] A cryptographic hash appended to a message to allow a receiver to ensure that the contents have not been changed in transit.
message digest	[Data Security] Synonym for hash value.
Message Digest 5	[Data Security] A message digest algorithm producing a 128-bit digest. This algorithm is deprecated for cryptographic use.
message digest algorithm	[Data Security] An algorithm that produces a secure hash.
metadata	[Data Management] Data associated with other data. Examples of metadata are protection information, time last accessed, and permissions.
metering	[Services] Measuring resources appropriate to the type of service.
Metropolitan Area Network	[Network] A network that connects nodes distributed over a city-wide area.
MIB	[Management] 1. [Management] Acronym for Management Information Base. 2. [Security] Men in Black
Mibit	[General] Shorthand for mebibit.
Mibyte	[General] Shorthand for mebibyte.
microwave-assisted magnetic recording	[Hardware] A recording technique that directs microwaves at the media of an HDD to aid the recording process. Abbreviated as MAMR.
migration	[Data Management] Movement of data or information between information systems, formats, or media. Migration is performed for reasons such as possible decay of storage media, obsolete hardware or software (including obsolete data formats), changing performance requirements (see tiered storage), or the need for cost efficiencies.
MIME	[Network] Acronym for Multipurpose Internet Mail Extensions.
mirror	[Storage System] A replica of a storage volume, consisting of separate components with identical contents on each component, that can be accessed independently by the storage system.
mirror	[Storage System] A RAID 1 volume, consisting of separate components with identical contents on each component, that can be accessed independently by the storage system.
mirrored array	[Storage System] A disk array that implements RAID Level 1.
mirrored disks	[Storage System] The disks of a mirrored array.
mirroring	[Storage System] Maintaining two or more separate, identical copies of data.
MLC	[Hardware] Acronym for multi-level cell
MMA	[Management] Acronym for Multipath Management API.
modal dispersion	[Network] Distortion in the optical signal transmitted through a multimode fiber caused by different time delays for the various modes of propagation. Modal dispersion results in a smearing of the signal edges that increases with the length of a fiber, thereby limiting the useful maximum length of a fiber as a function of the data rate.
model	[Management] A set of entities and the relationships among them that define the semantics, behavior, and state of that set.
modeling language	[Management] A language for describing the concepts of an information or data model. A popular modeling language in use today is UML (Unified Modeling Language).
MOF	[Management] Acronym for Managed Object Format.
monitor program	[Computer System] A program that keeps track of system resource utilization. Monitor programs typically record CPU utilization, I/O request rates, data transfer rates, RAM utilization, and similar statistics. A monitor program, which may be an integral part of an operating system, a separate software product, or a part of a related component, such as a database management system, is a necessary prerequisite to manual I/O load balancing.
mount	[File System] An operation that makes a block or file device, that is local or network attached, available to an operating system.
MTBF	[Computer System] Acronym for mean time between failures.
MTDL	[Computer System] Acronym for mean time to data loss.
MTTD	[General] Acronym for mean time to data.
MTTF	[General] Abbreviation for Mean Time to (first) Failure.
MTTR	[General] Acronym for mean time to repair.
MTU	[Network] Acronym for maximum transfer unit.
multi-actuator	[Hardware] The presence of more than one actuator within a single HDD.
multi-factor authentication	[Data Security] Verification of an individual's identity using more than one factor pertaining to knowledge, possession or biometrics. A knowledge factor is something an individual knows; a possession factor is something an individual has, and a biometric factor is something an individual is or is able to do.
multi-level cell	[Hardware] A solid state memory cell that stores two bits of data. Multi-level cell (MLC) is not a generic term for all memory cell types that store more than one bit.
multi-threaded	[Computer System] Having multiple concurrent or pseudo-concurrent execution sequences.
multicast	[Network] A single transmission of a message to a select subset of receivers connected to a transport network. Multicast is contrasted with broadcast (sending a message to all receivers on a network) and unicast (sending a message to a single receiver).
multicast group	[Network] A set of addresses that serves as the destination for multicast packets or frames.
multilevel security	[Data Security] A security system that allows users and resources of different sensitivity levels to access a system concurrently, while ensuring that only information for which the user or resource has authorization is made available.
multimode	[Network] Designed to carry multiple light rays or modes concurrently. In optical fiber, each mode is transmitted at a slightly different reflection angle within the optical fiber core. Multimode fiber transmission is used for relatively short distances.
multimode fiber optic cable	[Network] An optical fibre designed to carry multiple light rays or modes concurrently. In optical fiber, each mode is transmitted at a slightly different reflection angle within the optical fiber core. Multimode fiber transmission is used for relatively short distances.
multipath I/O	[Storage System] The facility for a host to direct I/O requests to a storage device on more than one access path.
Multipath Management API	[Management] A SNIA Standard for discovery and management of the multipath devices on a host system and the associated local and device ports.
multiprotocol storage	[Storage System] A storage system that provides consolidated file, block, object, and possibly other storage interfaces.
Multipurpose Internet Mail Extensions	[Network] A set of IETF specifications that define the mechanisms for specifying and describing the format of Internet message bodies. An HTTP response containing a Multipurpose Internet Mail Extensions (MIME) Content-Type header allows the HTTP client to invoke the appropriate application for processing the received data.
multitenancy	[Data Security] Allocation of physical and virtual resources such that multiple tenants and their computations and data are isolated from and inaccessible to one another. [ISO/IEC 17788]
mutual authentication	[Data Security] A process that verifies the identity of two entities prior to establishing communication between those entities.