Compaq StorageWorks HSG60 ACS Solution Software V8.6 for Compaq Tru64 UNIX Installation and Configuration Guide

Glossary–8 HSG60 ACS Solution Software Version 8.6 for Compaq Tru64 UNIX Installation and Configuration
Guide
host adapter A device that connects a host system to a SCSI bus. The host adapter usually
performs the lowest layers of the SCSI protocol. This function may be
logically and physically integrated into the host system.
hot disks A disk containing multiple hot spots. Hot disks occur when the workload is
poorly distributed across storage devices which prevents optimum subsystem
performance. See also hot spots.
hot spots A portion of a disk drive frequently accessed by the host. Because the data
being accessed is concentrated in one area, rather than spread across an array
of disks providing parallel access, I/O performance is significantly reduced.
See also hot disks.
hot swap A method of device replacement that allows normal I/O activity on a device
bus to remain active during device removal and insertion. The device being
removed or inserted is the only device that cannot perform operations during
this process. See also cold swap and warm swap.
hub A device (concentrator) which performs some or all of the following
functions:
■ Automatic insertion of operational loop devices without disrupting the
existing configuration.
■ Automatic removal of failed loop devices without impacting the existing
configuration.
■ Provides a centralized (star) wiring configuration and maintenance point.
■ Provides central monitoring and management.
IBR Initial Boot Record.
ILF Illegal function.
INIT Initialize input and output.
initiator A SCSI device that requests an I/O process to be performed by another SCSI
device, namely, the SCSI target. The controller is the initiator on the device
bus. The host is the initiator on the host bus.
instance code A four-byte value displayed in most text error messages and issued by the
controller when a subsystem error occurs. The instance code indicates when
during software processing the error was detected.
interface A set of protocols used between components, such as cables, connectors, and
signal levels.