Serial Attached SCSI technologies and architectures, 4th edition

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Appendix: SAS terminology
Table A-1 contains terms helpful in understanding SAS technology.
Table A-1: SAS terminology
Term
Definition
Domain
A set of SAS devices that communicate with one another through a service
delivery subsystem
Enterprise-class devices
SAS drives that provide maximum reliability, highest performance, scalability,
and error management. Typically used for unconstrained IO workloads in
mission-critical applications
Entry-level devices
SATA drives that provide a basic level of reliability and performance for non-
mission-critical environments
Expander
A device that functions as a switch to attach one or more initiators to one or
more targets
JBOD
A group of hard disks, usually in an enclosure, that may or may not be RAID
configured
Initiator
A device containing SSP, STP, or SMP initiator ports in a SAS domain
LFF
Large form factor (referring to 3.5-inch drives)
Midline devices
SAS and SATA drives that provide larger capacity, greater reliability, and
improved resistance to rotational and operational vibration than entry-level
devices.
PHY
The mechanism that connects the physical SAS layer to the SAS link layer
Physical link
Two differential signal pairs, one pair in each direction, that connect two PHYs
SAS address
The address of an initiator port, a target port, or an expander device
Serial ATA Tunneling
Protocol (STP)
A SAS protocol used to communicate with SATA drives
Serial Management
Protocol (SMP)
A SAS protocol used to communicate with SAS expanders
Serial SCSI Protocol (SSP)
A SAS protocol used to communicate with SAS drives
Service delivery subsystem
The part of a SAS system that sends information between a SAS initiator and a
SAS target
SFF
Small form factor (referring to 2.5-inch drives)
Target
An end device such as a SAS drive, SATA drive, or SAS tape drive
Training
The method of equalizing transmission signals at the receiver
Wide port
A port that contains more than one PHY
Zone group
A set of PHYs in a zone that all have the same access permission
Zoned portion of a service
delivery subsystem (ZPSDS)
Part of a service delivery subsystem that includes zoning expander devices
cooperating to control access between PHYs