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GL–18 Glossary
VHDCI Very High Density Cable Interface. A 68-pin interface. Required for
Ultra SCSI connections.
virtual terminal A software path from an operator terminal on the host to the controller’s CLI
interface, sometimes called a host console. The path can be established via
the host port on the controller (using HSZterm) or via the maintenance port
on the controller.
VTDPY Virtual Terminal Display utility.
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.
Worldwide name A unique 64-bit number assigned to a subsystem by the Institute of Electrical
and Electronics Engineers (IEEE) and set by Compaq 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’s 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
A cache management method used to decrease the subsystem’s response
time to a read. This method allows the controller to satisfy the request from
the cache memory rather than from the disk drives.
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.