HP StorageWorks HSG60 and HSG80 Array Controller and Array Controller Software Troubleshooting Guide (EK-G80TS-SA. C01, March 2005)

Glossary
301HSG60 and HSG80 Array Controller and Array Controller Software Troubleshooting Guide
VHDCI
Very High-Density-Cable Interface. A 68-pin interface that is required for Ultra SCSI
connections.
virtual terminal
A software path from an operator terminal on the host to the controller CLI, sometimes
called a host console. The path can be established through the host port on the controller or
through the maintenance port through an intermediary host.
See also maintenance terminal.
VTDPY
Virtual Terminal Display. A utility that allows viewing of specific informational displays
by using CLI commands.
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. Also called node
ID within the CLI.
write hole
The period of time in a RAID 1 or RAID 5 write operation at which 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.
writeback cache
See cache module.
writeback 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 the controller cache memory. The controller performs the slower operation of
writing the data to the disk drives at a later time.
write-through cache
A cache management technique for retaining host write requests in read cache. After 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.