Glossary

The module that transfers the external AC power supply into the power supply for internal use.

A service processing node (a computer device) on the network. Application programs of data services run on the application server.

A kind of remote replication. When the data at the primary site is updated, the data does not need to be updated synchronously at the mirroring site to finish the update. In this way, performance is not reduced due to data mirroring.

A collection of data stored on (usually removable) non-volatile storage media for purposes of recovery in case the original copy of data is lost or becomes inaccessible; also called a backup copy. To be useful for recovery, a backup must be made by copying the source data image when it is in a consistent state. The act of creating a backup.

An interval of time during which a set of data can be backed up without seriously affecting applications that use the data.

The numerical difference between the upper and lower frequencies of a band of electromagnetic radiation. A deprecated synonym for data transfer capacity that is often incorrectly used to refer to throughput.

The maximum rate of signal state changes per second on a communications circuit. If each signal state change corresponds to a code bit, then the baud rate and the bit rate are the same. It is also possible for signal state changes to correspond to more than one code bit, so the baud rate may be lower than the code bit rate.

An incompatibility between a bit in a transmitted digital signal and the corresponding bit in the received digital signal.

The probability that a transmitted bit will be erroneously received. The bit error rate (BER) is measured by counting the number of bits in error at the output of a receiver and dividing by the total number of bits in the transmission. BER is typically expressed as a negative power of 10.

A test methodology that uses shift registers in the output connections of integrated circuits (ICs). One IC is often connected to the next IC. A data pattern is passed through the chain and the observed returned data stream affected by the circuit conditions gives an indication of any faults present. The system is defined under IEEE standard 1149.1 and is also known as Joint Test Action Group (JTAG).

Architecture that defines the roles of the browser and server. The browser is the service request party and the server is the service provider.

The ratio of the number of cache hits to the number of all I/Os during a read task, usually expressed as a percentage.

Specially designed to lock into place on a parent board or motherboard, allowing for easy installation and removal of attached pieces without release of the screw.

A password-based authentication protocol that uses a challenge to verify that a user has access rights to a system. A hash of the supplied password with the challenge is sent for comparison so the cleartext password is never sent over the connection.

A technology for ensuring data security and integrity in a storage system. It is used to store the mission-critical data of the system.

Disks that build up the coffer.

The control logic in a disk or tape that performs command decoding and execution, host data transfer, serialization and deserialization of data, error detection and correction, and overall management of device operations. The control logic in a storage subsystem that performs command transformation and routing, aggregation (RAID, mirroring, striping, or other), high-level error recovery, and performance optimization for multiple storage devices.

An enclosure that accommodates controllers and provides storage services. It is the core component of a storage system and generally consists of components, such as controllers, power supplies, and fans.

A pair state. The state indicates that the source LUN data is being synchronized to the target LUN.

The process of encoding data to reduce its size. Lossy compression (i.e., compression using a technique in which a portion of the original information is lost) is acceptable for some forms of data (e.g., digital images) in some applications, but for most IT applications, lossless compression (i.e., compression using a technique that preserves the entire content of the original data, and from which the original data can be reconstructed exactly) is required.

A process that involves processing data extracted from the source system. These processes include: filtering, integration, calculation, and summary, finding and solving data inconsistency, and deleting invalid data so that the processed data meets the requirements of the destination system for the input data.

A 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, the need for cost efficiencies etc.

A system, database (database user; database instance), or file that can make BOs persistent.

The replacement of multiple copies of data — at variable levels of granularity — with references to a shared copy in order to save storage space and/or bandwidth.

Data that is stored temporarily on the cache and has not been written onto disks.

The recovery of data, access to data and associated processing through a comprehensive process of setting up a redundant site (equipment and work space) with recovery of operational data to continue business operations after a loss of use of all or part of a data center. This involves not only an essential set of data but also an essential set of all the hardware and software to continue processing of that data and business. Any disaster recovery may involve some amount of down time.

A set of disks from one or more commonly accessible disk subsystems, combined with a body of control software. The control software presents the disks' storage capacity to hosts as one or more virtual disks. Control software is often called firmware or microcode when it runs in a disk controller. Control software that runs in a host computer is usually called a volume manager.

A disk domain consists of the same type or different types of disks. Disk domains are isolated from each other. Therefore, services carried by different disk domains do not affect each other in terms of performance and faults (if any).

Consists of the following parts in redundancy: expansion module, disk, power module, and fan module. System capacity can be expanded by cascading multiple disk enclosures.

The process of locating a disk in the storage system by determining the enclosure ID and slot ID of the disk.

The percentage of used capacity in the total available capacity.

A component used for expansion.

Connects a storage system to more disk enclosures through connection cables, expanding the capacity of the storage system.

A unit or component of a system that is designed to be replaced in the field, i.e., without returning the system to a factory or repair depot. Field replaceable units may either be customer-replaceable or their replacement may require trained service personnel.

Low-level software for booting and operating an intelligent device. Firmware generally resides in read-only memory (ROM) on the device.

Flash Translation Layer (FTL) organizes and manages host data, enables host data to be allocated to NAND flash chips of SSDs in an orderly manner, maintains the mapping relationship between logical block addresses (LBAs) and physical block addresses (PBAs), and implements garbage collection, wear leveling, and bad block management.

The port that connects the controller enclosure to the service side and transfers service data. There are three types of front-end ports: SAS, Fibre Channel, and iSCSI.

The process of reclaiming resources that are no longer in use. Garbage collection has uses in many aspects of computing and storage. For example, in flash storage, background garbage collection can improve write performance by reducing the need to perform whole block erasures prior to a write.

A device that receives data via one protocol and transmits it via another.

With a view to defragmentation of storage arrays and garbage collection of disks, global garbage collection reduces garbage of disks by enabling storage arrays to inform disks of not implementing invalid data relocation and of controlling space release so that disks and controllers consume less space, reducing costs and prolonging the useful life of storage arrays.

The second-generation mobile networking standard defined by the European Telecommunications Standards Institute (ETSI). It is aimed at designing a standard for global mobile phone networks. GSM consists of three main parts: mobile switching subsystem (MSS), base station subsystem (BSS), and mobile station (MS).

With a view to individual characteristics of a single disk, global wear leveling uses space allocation and write algorithms to achieve wear leveling among disks, preventing a disk from losing efficacy due to excessive writes and prolonging the useful life of the disk.

The tray that bears the hard disk.

Heartbeat supports node communication, fault diagnosis, and event triggering. Heartbeats are protocols that require no acknowledgement. They are transmitted between two devices. The device can judge the validity status of the peer device.

The ratio of directly accessed I/Os from the cache to all I/Os.

The substitution of a replacement unit (RU) in a system for a defective unit, where the substitution can be performed while the system is performing its normal functioning normally. Hot swaps are physical operations typically performed by humans.

The management control information of the network and the carrier service information of the user network are transferred through the same logical channel. In-band management enables users to manage storage arrays through commands. Management commands are sent through service channels, such as I/O write and read channels. The advantages of in-band management include high speed, stable transfer, and no additional management network ports required.

The system component that originates an I/O command over an I/O interconnect. The endpoint that originates a SCSI I/O command sequence. I/O adapters, network interface cards, and intelligent I/O interconnect control ASICs are typical initiators.

Shorthand for input/output. I/O is the process of moving data between a computer system's main memory and an external device or interface such as a storage device, display, printer, or network connected to other computer systems. This encompasses reading, or moving data into a computer system's memory, and writing, or moving data from a computer system's memory to another location.

A replaceable field module that accommodates the service or management ports.

A method of adjusting the system, application components, and data to averagely distribute the applied I/Os or computing requests to physical resources of the system.

The addressable entity within a SCSI target that executes I/O commands.

The SCSI identifier of a logical unit within a target. Industry shorthand, when phrased as "LUN", for the logical unit indicated by the logical unit number.

The process of writing 0 bits in the data area of the logical drive and generating related parity bits so that the logical drive can be in the ready state.

A storage system maps LUNs to application servers so that application servers can access storage resources.

A method for the LUN data to migrate between different physical storage spaces while ensuring data integrity and uninterrupted operation of host services.

A type of snapshot created for a LUN. This snapshot is both readable and writable and is mainly used to provide a snapshot LUN from point-in-time LUN data.

A computer connected through a serial port or management network port. It maintains the storage system.

The module that integrates one or more management network ports.

An entity that provides means to transmit and process network management information.

The network port on the controller enclosure connected to the maintenance terminal. It is provided for the remote maintenance terminal. Its IP address can be modified with the change of the customer's environment.

A host controller interface with a register interface and command set designed for PCI Express-based SSDs.

A solid state disk (SSD) with a non-volatile memory express (NVMe) interface. Compared with other SSDs, such SSDs can deliver higher performance and shorter latency.

A management mode used during out-of-band networking. The management and control information of the network and the bearer service information of the user network are transmitted through different logical channels.

When an external power failure occurs, the AC PEM depends on the battery for power supply. This ensures the integrity of the dirty data in the cache.

When the system monitors a failing member disk in a RAID group, the system copies the data from the disk to a hot spare disk in advance.

A palm-sized NVMe SSD is a type of NVMe SSD of which the dimensions (H x W x D) are 160 mm x 79.8 mm x 9.5 mm (neither 3.5-inch nor 2.5-inch).

The application of different redundancy types to a logical drive. A RAID level improves the fault tolerance or performance of the logical drive but reduces the available capacity of the logical drive. You must specify a RAID level for each logical drive.

The regeneration and writing onto one or more replacement disks of all of the user data and check data from a failed disk in a mirrored or RAID array. In most arrays, a rebuild can occur while applications are accessing data on the array's virtual disks.

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.

A core technology for disaster recovery and a foundation that implements remote data synchronization and disaster recovery. This technology remotely maintains a set of data mirrors through the remote data connection function of the storage devices that are separated in different places. Even when a disaster occurs, the data backup on the remote storage device is not affected. Remote replication can be divided into synchronous remote replication and asynchronous remote replication.

The process of restoring data from the redundancy machine (RM) when the services of the production machine (PM) are recovering.

The path that network traffic takes from its source to its destination. On a TCP/IP network, each IP packet is routed independently. Routes can change dynamically.

A parameterized list of primitive I/O interconnect operations intended to be executed in sequence. Often used with respect to ports, most of which are able to execute scripts of I/O commands autonomously (without policy processor assistance). A sequence of instructions intended to be parsed and carried out by a command line interpreter or other scripting language. Perl, VBScript, JavaScript and Tcl are all scripting languages.

An input/output location (channel) that sends and receives data (one bit at a time) to and from the CPU of a computer or a communications device. Serial ports are used for serial data communication and as interfaces for some peripheral devices, such as mouse devices and printers.

The user and/or network information required for the normal functioning of services.

The network port that is used to store services.

An IETF protocol for monitoring and managing systems and devices in a network. The data being monitored and managed is defined by an MIB. The functions supported by the protocol are the request and retrieval of data, the setting or writing of data, and traps that signal the occurrence of events.

One component or path in a system, the failure of which would make the system inoperable.

A position defined by an upper guide rail and the corresponding lower guide rail in a frame. A slot houses a board.

A collection of ANSI standards and proposed standards that define I/O interconnects primarily intended for connecting storage subsystems or devices to hosts through host bus adapters. Originally intended primarily for use with small (desktop and desk-side workstation) computers, SCSI has been extended to serve most computing needs, and is arguably the most widely implemented I/O interconnect in use today.

A point in time copy of a defined collection of data. Clones and snapshots are full copies. Depending on the system, snapshots may be of files, LUNs, file systems, or any other type of container supported by the system.

A copy of a snapshot LUN.

The LUN where the original data is located.

An integrated system that consists of the following parts: controller, storage array, host bus adapter, physical connection between storage units, and all control software.

An abstract definition of backup storage media for storing backup data. The storage unit is connected to the actual storage media used to back up data.

Streaming media is media continuously streamed over the network. Combining technologies concerning streaming media data collection, compression, encoding, storage, transmission, playback, and network communications, streaming media can provide high-quality playback effects in real time at low bandwidth.

A type of smaller network that forms a larger network according to a rule, such as, forming a network according to different districts. This facilitates the management of a large network.

The endpoint that receives a SCSI I/O command sequence.

The LUN on which target data resides.

A logic disk that can be accessed by hosts. It dynamically allocates storage resources from the thin pool according to the actual capacity requirements of users.

The logical layout of the components of a computer system or network and their interconnections. Topology deals with questions of what components are directly connected to other components from the standpoint of being able to communicate. It does not deal with questions of physical location of components or interconnecting cables. The communication infrastructure that provides Fibre Channel communication among a set of PN_Ports (e.g., a Fabric, an Arbitrated Loop, or a combination of the two).

A method by which the host operating system may inform a storage device of data blocks that are no longer in use and can be reclaimed. Many storage protocols support this functionality via various names, e.g., ATA TRIM and SCSI UNMAP.

The space where users interact with a machine.

A set of algorithms utilized by a flash controller to distribute writes and erases across the cells in a flash device. Cells in flash devices have a limited ability to survive write cycles. The purpose of wear leveling is to delay cell wear out and prolong the useful life of the overall flash device.

Increase in the number of write operations by the device beyond the number of write operations requested by hosts.

The ratio of the number of write operations on the device to the number of write operations requested by the host.

A caching technology in which the completion of a write request is signaled as soon as the data is in the cache. Actual writing to non-volatile media occurs at a later time. Write back includes inherent risks: an application will take action predicated on the write completion signal, and a system failure before the data is written to non-volatile media will cause media contents to be inconsistent with that subsequent action. For these reasons, sufficient write back implementations include mechanisms to preserve cache contents across system failures (including power failures) and a flushed cache at system restart time.

A type of storage, designed for fixed content, that preserves what is written to it in an immutable fashion. Optical disks are an example of WORM storage.

A caching technology in which the completion of a write request is not signaled until data is safely stored on non-volatile media. Write performance equipped with the write through technology is approximately that of a non-cached system. However, if the written data is also held in a cache, subsequent read performance may be dramatically improved.