HP StorageWorks XP Performance Advisor Software v4.6 User and Troubleshooting Guide (T1789-96094, June 2010)

Glossary
ACP Array Control Processor
ACP handles the transfer of data between the cache and the physical drives held
in the DKUs. ACPs work in pairs, providing a total of eight SCSI buses. Each
SCSI bus associated with one ACP is paired with a SCSI bus on the other ACP
pair element. In the event of an ACP failure, the redundant ACP takes control.
Both ACPs work together by sharing the load. On XP models, such as the
XP10000, this function is handled by the disk adapter on the MIX board.
ACP was used on XP disk arrays before the advent of the XP24000 type arrays.
With the introduction of XP24000, DKA replaced ACP.
XP Continuous
Access
The HP StorageWorks XP Continuous Access is a software providing remote
replication between XP disk arrays and is used for disaster recovery. XP
Continuous Access is referred to as XP Continuous Access in official HP
documents.
Cache A Cache is a high speed memory that is used to speed up the IO/s transaction
time. All reads and writes to the XP arrays are sent to the cache. The data is
buffered in the cache until it is transferred to the physical disks or from the physical
disks (with slower data throughput) is complete. The benefit of cache memory is
that it speeds the IO/s throughput to the application. The larger the cache size,
the greater the amount of data buffering that can occur and the greater throughput
to the applications. In the event of power loss, the battery power maintains the
contents of cache for a specified time period.
XP Continuous
Access Journal
The HP StorageWorks XP Continuous Access Journal is an asynchronous mirroring
program similar to the XP Continuous Access Async Software, except that the
transactions to be written to the secondary XP array are maintained in a
disk-based journal file. This provides better performance for secondary XP array
systems that are not highly available or that may be subject to bandwidth
contention from other applications.
CFW Cache Fast Write
The CFW is a 3990-3/6 function that can be used with volatile data. It is also
a form of fast write where the subsystem writes the data directly to the cache,
which is made available for later destaging activity.
CH Channel
Description 1: A path along which signals can be sent; for example, data channel
and output channel.
Description 2: A functional unit controlled by the processor; handles the transfer
of data between processor storage and local peripheral equipment on mainframe
environments.
CHA Channel Adapter. CHA provides an interface between an XP disk array and the
external host system. Occasionally, this term is used synonymously with the term
channel host interface processor (CHIP).
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