HP StorageWorks HSG80 ACS Solution Software V8.8 for IBM AIX Installation and Configuration Guide (AA-RV1HA-TE, March 2005)

Glossary
255HSG80 ACS Solution Software V8.8 for IBM AIX Installation and Configuration Guide
warm swap A device replacement method that allows the complete system to
remain online during device removal or insertion. The system bus may
be halted, or quiesced, for a brief period of time during the warm-swap
procedure.
Wide Ultra SCSI Fast/20 on a Wide SCSI bus.
Worldwide
name
A unique 64-bit number assigned to a subsystem by the Institute of
Electrical and Electronics Engineers (IEEE) and set by manufacturing
prior to shipping. This name is referred to as the node ID within the
CLI.
write-back
caching
A cache management method used to decrease the subsystem response
time to write requests by allowing the controller to declare the write
operation “complete” as soon as the data reaches its cache memory.
The controller performs the slower operation of writing the data to the
disk drives at a later time.
write-through
caching
Write-through caching always writes directly to disk, ensuring that the
application is never tricked into believing that the data is on the disk
when it may not be. This results in highest data integrity, though with
slightly reduced performance.
write hole The period of time in a RAID level 1 or RAID level 5 write operation
when an opportunity emerges for undetectable RAIDset data
corruption. Write holes occur under conditions such as power outages,
where the writing of multiple members can be abruptly interrupted. A
battery backed-up cache design eliminates the write hole because data
is preserved in cache and unsuccessful write operations can be retried.
write-through
cache
A cache management technique for retaining host write requests in
read cache. When the host requests a write operation, the controller
writes data directly to the storage device. This technique allows the
controller to complete some read requests from the cache, greatly
improving the response time to retrieve data. The operation is complete
only after the data to be written is received by the target storage device.
This cache management method may update, invalidate, or delete data
from the cache memory accordingly, to ensure that the cache contains
the most current data.