[Data Security] Acronym for Remote Authentication Dial In User Service.
[Storage System] Acronym for Redundant Array of Independent Disks.
The phrase Redundant Array of Independent Disks is adapted from the 1988 SIGMOD paper A Case for Redundant Arrays of Inexpensive Disks.
[Storage System] Synonym for data striping.
[Storage System] Synonym for mirroring.
[Storage System] A form of parity RAID in which the disks operate independently, the data stripe size is no smaller than the exported block size, and parity check data is distributed across the RAID array's disks.
[Storage System] Shorthand for Redundant Array of Independent Disks.
[Storage] Acronym for Redundant Array of Independent Nodes.
[General] An elevated floor providing space for cable runs between equipment cabinets and cold air flow for cooling.
Many mainframe systems are designed to intake cool air from the bottom and exhaust heat from the top of a closed cabinet system.
[Storage System] A quantity of host system random access memory (RAM) managed by software and presented to applications as a high-performance disk.
RAMdisks generally emulate disk I/O functional characteristics, but unless augmented by special hardware to make their contents non-volatile, they cannot tolerate loss of power without losing data. See solid state disk.
[Storage System] Any I/O load whose consecutively issued read and/or write requests do not specify adjacently addressed data.
The term random I/O is commonly used to denote any I/O load that is not sequential, whether or not the distribution of data locations is indeed random. Random I/O is characteristic of I/O request-intensive applications. See sequential I/O.
[General] A number having properties of randomness or unpredictability.
There are three basic classes of random number. Deterministic or pseudorandom numbers are generated by an algorithm that produces a predictable sequence of values from an initial value called a seed. Cryptographically secure random numbers are produced in a sequence that, while deterministic, cannot be feasibly discovered or computed by examination of previous numbers in the sequence. Nondeterministic generators incorporate input from some unpredictable physical source that is outside human control.
[Fibre Channel] A transmission control algorithm in which the frames containing the subblocks that comprise a block of information may be transmitted in any order.
Because of the diversity of meanings attached to this term by disk subsystem developers, SNIA publications make minimal use of it.
[Computer System] Quick scaling of resources and capabilities to meet expansion and contraction of demand.
To the consumer, the capabilities available for provisioning often appear to be unlimited and available for purchase in any quantity at any time.
[Computer System] Quickly and automatically deploying services in response to requests.
1. [Computer System] Acronym for Reliability, Availability, and Serviceability.
2. [Windows] Acronym for Remote Access Server (Windows NT dialup networking server).
[Storage System] The sum total amount of addressable capacity of the storage devices in a storage system.
The addressable capacity of a storage device is commonly understood to be the number of bytes available to be written via SCSI or equivalent protocol. It does not include unaddressable space, ECC (error correcting code) data, remap areas, inter-sector gaps and so on. See theoretical capacity.
The term raw partition is frequently encountered when discussing database systems because some database system vendors recommend volumes or files for underlying database storage, while others recommend direct storage on raw partitions.
[Data Recovery] A bit-by-bit copy of a partition image.
[Data Security] Acronym for Role-Based Access Control.
[Storage System] The magnetic or optical recording device in a disk.
Read/write heads are used both to write data by altering the recording media’s state, and to read data by sensing the alterations. Disks typically have read/write heads, unlike tapes, in which reading and writing are often done using separate heads.
[Storage System] Synonym for idle.
[Storage System] Deprecated synonym for mirroring.
[Storage System] Synonym for inline data deduplication.
In most arrays, a rebuild can occur while applications are accessing data on the array’s virtual disks.
1. [General] An interconnect or network device that includes a detector and signal processing electronics.
3. [Fibre Channel] The portion of a Link_Control_Facility dedicated to receiving an encoded bit stream, converting the stream into transmission characters, and decoding the characters using the rules specified by FC-0.
[Storage System] Synonym for rebuilding.
[Data Recovery] Synonym for media ID.
[Data Recovery] The recreation of a past operational state of an entire application or computing environment.
Recovery is required after an application or computing environment has been destroyed or otherwise rendered unusable. It may include restoration of application data, if that data had been destroyed as well.
[Data Recovery] The maximum acceptable time period prior to a failure or disaster during which changes to data may be lost as a consequence of recovery.
Data changes preceding the failure or disaster by at least this time period are preserved by recovery. Zero is a valid value and is equivalent to a "zero data loss" requirement.
[Data Recovery] The maximum acceptable time period required to bring one or more applications and associated data back from an outage to a correct operational state.
[Storage System] Synonym for degraded mode.
Reduction most often occurs because of member disk failure, however, some RAID implementations allow reduction for system management purposes.
[General] The inclusion of extra components of a given type in a system (beyond those required by the system to carry out its function) for the purpose of enabling continued operation in the event of a component failure.
[Storage System] A collection of extents organized for the purpose of providing data protection.
Within a redundancy group, a single type of data protection is employed. All of the usable storage capacity in a redundancy group is protected by check data stored within the group, and no usable storage external to a redundancy group is protected by check data within it.
[Computer System] Components of a system that have the capability to substitute for each other when one of the components fails, so that the system can continue to perform its function.
In storage subsystems, power distribution units, power supplies, cooling devices, and controllers are often configured to be redundant. The disks comprising a mirror set are redundant. A parity RAID array’s member disks are redundant, since surviving disks can collectively replace the function of a failed disk.
The redundant information enables regeneration of user data in the event that one of the array's member disks or the access path to it fails. Although it does not conform to this definition, disk striping is often referred to as RAID (RAID Level 0). See Berkeley RAID levels.
[Storage] A collection of networked server nodes with software that provides and maintains pools of highly available storage capacity.
[Data Management] Synonym for fixed content.
[Data Management] Synonym for fixed content.
1. [General] Synonym for beer.
Regeneration may also be used to recover data from an unrecoverable media error. Data in a parity RAID array is regenerated by computing the exclusive OR of the contents of corresponding blocks from the array's remaining disks. Data in a RAID Level 6 array is regenerated by choosing the more convenient of two parity algorithms and executing it.
[Storage System] To bring a split mirror component back into the mirror.
When the resilvering process completes, the mirror component becomes identical to all mirror components in the mirror.
[Data Security] The process of changing the key used for an ongoing communication session.
[Fibre Channel] A displacement, expressed in bytes, used to divide a quantity of data into blocks and subblocks for transmission in separate frames.
Relative offsets are used to reassemble data at the receiver and verify that all data has arrived.
The range starts at zero, representing the upper level-defined-origin, and extends to a highest value. Relative offset values are required to lie within the appropriate relative offset space.
Information such as username and password is entered when a connection is made. This information is passed to a RADIUS server that verifies the information in order to authorize access to the system. RADIUS is defined in RFC 2865.
removable media library
[Backup] Synonym for library.
[Storage System] A storage device designed so that its storage volumes can be readily removed and inserted.
Tapes, CD-ROMs, and optical disks are removable media devices.
[General] A component or collection of components in a system that are always replaced (swapped) as a unit when any part of the collection fails.
Replacement units may be field replaceable, or they may require that the system of which they are part be returned to a factory or repair depot for replacement. Field replaceable units may be customer replaceable, or their replacement may require trained service personnel. Typical replacement units in a disk subsystem include disks, controller logic boards, power supplies, cooling devices, and cables. Replacement units may be cold swappable, warm swappable, or hot swappable.
2. [Data Recovery] An image of data usable by one or more applications without an intermediate restore process.
See backup copy.
2. [Data Recovery] The action of making a replicate as defined above.
[Storage System] A physical and logical connection that transports data and replication control commands between primary and secondary sites.
[Storage System] A pair of volumes that have a replication relationship.
A replication set consists of a primary volume and a secondary volume that are physically separated. The replication set also defines how the primary and secondary volumes are connected and how replication ought to proceed.
[Services] A specific set of principles for defining, addressing and interacting with resources addressable by URIs.
Architectures that follow these principles are said to be RESTful. The principles include: abstraction of state into resources and a uniform set of representations and operations (e.g., HTTP verbs like GET and PUT as the only means to manipulate a resource). RESTful interfaces are contrasted with Web Services interfaces such as WBEM, which tend to be RPC-like.
[Data Security] The act of a principal in denying, disowning or disavowing an act, event or transaction.
[Data Security] Internet -related specifications, including standards, experimental definitions, informational documents and best practice definitions, produced by the IETF.
[Computer System] A characterization of I/O intensive applications.
Request-intensive applications' I/O requests are usually randomly addressed and often specify a small amount of data for transfer.
1. [General] In a standard, a field in a data structure set aside for future definition.
Some standards prescribe implementation behavior with respect to reserved fields (e.g., originators of data structures containing reserved fields must zero fill them; consumers of data structures containing reserved fields must ignore them, etc.); others do not.
2. [Fibre Channel] A field filled with binary zeros by a source N_Port and ignored by a destination N_Port.
Each bit in a reserved field is denoted by "r" in the Fibre Channel standards. Future enhancements to Fibre Channel Standards may define usages for reserved fields. Implementations should not check or interpret reserved fields. Violation of this guideline may result in loss of compatibility with future implementations that comply with future enhancements to Fibre Channel Standards.
[Data Recovery] [Storage Systems] Synonym for mirror resynchronization.
[Computer System] Aggregation of a provider’s computing resources to serve multiple consumers using a multitenant model, with physical and virtual resources dynamically assigned and reassigned on demand.
An RX_ID is meaningful only to the responder that originates it.
[Services] Abbreviation for Representational State Transfer.
[Data Recovery] Synonym for recovery.
1. [Data Recovery] The length of time that a backup image should be kept.
2. [File System] In some file systems, such as that shipped with IBM Corporation's OS/390 operating system, a property of a file that can be used to implement backup and data migration policies.
[Data Management] A policy governing when and for how long a record must be retained by a storage system.
This may be a rule that applies to groups or categories of records, or may be specified for individual records. The policy may be time or event based.
[Computer System] A circuit that uses a clock independent of the incoming signal to generate an outbound signal.
[Data Communication] The ratio of the strength of a returned signal to that of the incident signal that caused it.
In electrical circuits, return loss is caused by impedance discontinuities. Optical return loss is caused by index of refraction differences.
[Storage System] An operation performed on a split mirror component, in order to use its data as the basis for the mirror as a whole.
When a component is reverse rejoined, all mirror components in the mirror become identical to the previously split mirror component as a result of the resilver process.
[Data Security] Acronym for Request For Comment.
[Data Security] The potential that a given threat will exploit vulnerabilities of an asset or group of assets to cause loss or damage to the assets [IEEE 13335-1:1996].
[Data Security] Decision to accept a risk.
[Data Security] The process of identifying security risks, determining their magnitude, and identifying areas needing safeguards [IEEE 13335-1:1996].
[Data Security] The process of assessing and quantifying risk and establishing an acceptable level of risk for the organization [IEEE 13335-1:1996].
[Data Security] Process of selection and implementation of measures to modify risk.
[Storage System] The mechanical component of a library which moves removable volumes among drives and entry/exit slots.
2. [File System] In LTFS, the process of modifying the index to match a previous version of the index.
Exact rotational latencies for specific sequences of I/O operations can only be obtained by detailed disk drive simulation or measurement. The simplifying assumption that on average, requests wait for half a disk revolution time of rotational latency works well in practice. Half of a disk revolution time is therefore defined to be the average rotational latency.
[Fibre Channel] An entity that resides in an Inter-Fabric Router and is responsible for the forwarding of frames between independent Fabrics including the translation of N_Port_ID’s to present the Proxy N_Ports to the local Fabrics.
[Data Recovery] Acronym for Recovery Point Objective.
[Data Security] Acronym for both a public key algorithm and a corporation in the business of algorithm design, derived from the names of its founders (Rivest, Shamir & Adelman).
[Fibre Channel] Acronym for Registered State Change Notification.
[Data Recovery] Acronym for Recovery Time Objective.
[General] Acronym for Replaceable Unit.
[Data Communication] The number of consecutive identical bits in a transmitted signal. For example, the pattern 0011111010 has run lengths of 2, 5, 1, 1, and 1.
[Data Recovery] Acronym for Recorded Volume Serial Number.