HP StorageWorks Data Replication Manager HSG80 ACS Version 8.7P Configuration Guide (AA-RPHZF-TE, March 2004)

Glossary
238 Data Replication Manager HSG80 ACS Version 8.7P Configuration Guide
asynchronous mode
A mode of operation of the remote copy set whereby the write operation provides command completion to the
host after the data is safe on the initiating controller, and prior to the completion of the target command.
Asynchronous mode can provide faster response time, but the data on all members at any one point in time
cannot be assumed to be identical.
See also synchronous mode.
ATM
Asynchronous Transfer Mode. ATM refers to a network or communications technology used in LANs and
WANs to enable disparate traffic (data, voice, and video) to be carried over the same local or wide area network.
ATM is the transfer mode of choice for broadband integrated services digital networks (BISDNs). ATM traffic
carries information in fixed-size cells.
autospare
A controller feature that automatically replaces a failed disk drive with a working drive. The operator can enable
the AUTOSPARE switch for the failedset, causing physically replaced disk drives to be automatically placed
into the spareset. Data recovery is outside the scope of autosparing. Also called autonewspare.
B-series switches
Fibre Channel core and SAN switches made by Brocade and sold by HP.
bad block
A disk drive data block that contains a physical defect.
bad block replacement
A replacement routine that substitutes defect-free disk blocks for those found to have defects. This process takes
place in the controller, transparent to the host.
BBR
See bad block replacement.
block
A stream of data stored on disk or tape media and transferred and error-checked as a unit. In a disk drive, a block
is also called a sector (the smallest collection of consecutive bytes addressable on a disk drive). In HP integrated
storage elements, a block contains 512 bytes of data, error codes, flags, and the block address header.
C-series switches
Switches made by Cisco.
cache
A fast, temporary storage buffer in a controller or computer.
cache memory
Portion of high-speed memory used as an intermediary between a data user and a larger amount of storage. The
objective of designing cache into a system is to improve performance by placing the most frequently used data
in the highest performance memory and close to the process needing that data.
CBR
An acronym for Constant Bit Rate, a category of ATM service. This category supports a constant (guaranteed)
data rate. CBR supports applications that require a highly predictable transmission rate.
cascaded switch
As applied to the Data Replication Manager, the term cascaded switch identifies that the output of a switch is
connected to the input of another switch, which then may in turn be connected to another switch or host or
controller.
chunk
A block of data written by the host.
See also block, chunk size.