An identifier assigned to a SCSI port or SCSI logical unit. SAM identifiers are used to facilitate communication.
SAM logical unit identifier
An identifier that is unique within the context of the SCSI port through which the logical unit is accessed. The identifier assigned to a logical unit can change. A SAM logical unit identifier is commonly called a SCSI logical unit number (LUN).
SAM name
An identifier assigned to a SCSI device or SCSI port that is globally unique within the context of the SCSI Transport Protocol implemented by the SCSI device. SCSI names are used to positively identify a SCSI device or SCSI port. SCSI names never change.
SAM port identifier
An identifier that is unique within the context of the SCSI service delivery subsystem to which the port is connected. The identifier assigned to a SCSI port can change.
SAN manager
See fabric manager.
SCSI application client
The SCSI protocol implemented in an initiator.
SCSI application protocol
A generic term encompassing both the SCSI application client and the SCSI logical unit.
SCSI asynchronous mode
A mode of communication in which each request must be acknowledged before another request can be issued.
SCSI Command Descriptor Block (CDB)
The data structure by which a SCSI command is conveyed from an initiator to a target.
SCSI device
A NIC, HBA, or other endpoint that contains one or more ports and supports the SCSI protocol.
SCSI domain
A complete I/O system composed of SCSI devices that contain SCSI ports that communicate via a SCSI service delivery subsystem.
SCSI enclosure
A chassis that contains one or more SCSI devices.
SCSI identifier (SCSI ID)
The SPI term for SAM port identifier.
SCSI initiator
The device that initiates a transfer of data between two SCSI devices.
SCSI interconnect
A networking technology that can be used to facilitate communication between SCSI ports. A SCSI interconnect developed specifically for the SCSI protocol may transport the SCSI protocol natively. A general-purpose SCSI interconnect requires a SCSI Transport Protocol.
SCSI logical unit (LU)
The processing entity within a SCSI target device that presents a storage medium to SCSI application clients and executes SCSI commands on that medium.
SCSI Logical Unit Number (LUN)
The address assigned to a logical unit. From the perspective of a host, a LUN is often called a volume.
SCSI Parallel Interface (SPI)
A physical and electrical interface specification supporting parallel transmission in a bus topology.
SCSI port
A port in a SCSI device.
SCSI service delivery subsystem
A generic term that refers to a SCSI interconnect technology or the combination of a SCSI interconnect technology and a SCSI Transport Protocol.
SCSI synchronous mode
A mode of communication in which one or more requests can be issued without first receiving acknowledgement for previously issued requests.
SCSI target
The device that responds to a request for transfer of data between two SCSI devices.
SCSI transport protocol
A protocol mapping that enables the SCSI protocol to be transported on a general-purpose SCSI Interconnect.
SCSI-3 extended copy
A SCSI-3 command that enables a third-party device (neither the initiator nor the target) to control the movement of data as requested by a SCSI initiator.
segmentation
The process by which an end node segments a large chunk of ULP data into multiple smaller chunks that can be framed for transmission without exceeding the MTU of the egress port in the NIC, HBA, or other network interface.
semiconductor optical amplifier (SOA)
A device that converts an optical signal to an electrical signal, amplifies it, and then converts it back to optical.
sequence qualifier
A sequence identifier that is guaranteed to be unique during the R_A_TOV and is composed of the S_ID, D_ID, OX_ID, RX_ID, and SEQ_ID fields of the header of a Fibre Channel frame. The sequence qualifier is used for error recovery.
Sequence Status Block (SSB)
A small area in memory used to maintain the state of each FC Sequence.
Serial ATA (SATA)
A new series of specifications for ATA operation on serial bus interfaces.
Serial Attached SCSI (SAS)
A new series of specifications for SCSI operation on serial bus interfaces.
Server Message Block (SMB)
The predecessor to CIFS.
server-free backup
A technique for backing up data that removes the requesting server from the data path and confines the data path to a SAN.
Service Access Point (SAP)
The interface between vertically stacked OSI layers.
Service Data Unit (SDU)
The PDU of an OSI layer from the viewpoint of the lower neighbor layer.
Signal-to-Noise Ratio (SNR)
An expression of the strength of data-bearing signals relative to the strength of non-data-bearing signals present on a conductor.
silent discard
To drop a frame or packet without any notification to the source node or the ULP. The dropped frame or packet may be counted in an error log.
Single-Byte Command Code Set (SBCCS)
The block-multiplexer protocol historically used in mainframes. See also Enterprise Systems Connection (ESCON) and Fibre Channel Connection (FICON).
Small Computer System Interface (SCSI)
The block-level protocol historically used in open systems such as workstations and high-end server platforms. See also direct attached storage (DAS).
Small Form-Factor Pluggable (SFP)
A relatively new type of gigabit interface converter (GBIC) in smaller physical form that allows higher port density on switch and router line cards.
Spatial Reuse Protocol (SRP)
A protocol developed by Cisco Systems that optimizes bandwidth in ring topologies.
SPI
See SCSI parallel interface.
starvation
A condition in which some nodes are denied sufficient access to a medium to sustain normal communication sessions.
Storage Area Network (SAN)
A generic term referring to any network dedicated to the transport of block-level storage protocols.
storage channel
A communication architecture used by mainframes to access storage.
Storage Resource Management (SRM)
A storage management application that provides the ability to discover, inventory, and monitor disk and tape resources. Automated storage provisioning and reclamation functions are also supported by some SRM applications. Some SRM applications also support limited SAN management functionality.
storage subsystem
A chassis or set of modular enclosures that contain disks. Storage subsystems typically contain one or more disk controllers and support advanced functionality such as caching, RAID (mirroring and striping), and LUN management. This term is interchangeable with storage array.
store-and-forward switching
A method of switching in which the forwarding of each frame begins after the entire frame has been received. As soon as sufficient header information is received to make a forwarding decision, the switch makes a forwarding decision but does not begin transmitting until the rest of the frame is received. This method is currently the de facto standard for Ethernet switching in non-HPC environments.
stripe set
A set of partitions on physically separate disks to which data and optional parity blocks are written. One block is written to one partition, then another block is written to another partition, and so on until one block is written to each partition. The cycle then repeats until all blocks are written. The set of partitions is presented to applications as a single logical partition.
switch
A multiport bridge that employs a mechanism for internal port inter-connection. A switch has the ability to simultaneously forward frames at line rate across multiple ports. A switch typically employs advanced intelligence for processing frames.
Switch Internal Link Service (SW_ILS)
Special Fibre Channel procedures and frame payloads that provide advanced low-level networking functions and operate internal to a fabric (that is, between switches).
switching
The combined act of making forwarding decisions based on OSI Layer 2 information and forwarding frames.
Synchronous Digital Hierarchy (SDH)
A physical layer wide area transport technology based on time division multiplexing. SDH is an international standard.
Synchronous Optical Network (SONET)
A physical layer wide area transport technology based on time division multiplexing. SONET is a North American standard.
synchronous replication
A method of replicating data across long distances in which the states of the source and destination disk images are never more than one write request out of sync at any point in time. Both the source and destination disk devices must successfully complete the write request before SCSI status is returned to the initiator.
