HP StorageWorks EVA Controller HSG V8.8 Software - Manual (Page 143)

Glossary
143 Command Console V2.5 User Guide
virtual disk
A series of physical drives linked together so that the software
interprets the drives as being a single device. Logical storage
units are called virtual disks and are accessible by the host.
Each virtual disk has its own user-configurable parameters.
Some controllers use RAID techniques to provide virtual disks
with various cost, availability, and performance options.
Also called logical drives, volumes, volume sets, logical
storage units, logical units, units, and LUNs.
warm swap
In some controllers, a feature that allows devices to be added,
removed, or replaced while the subsystem remains operational,
but with all activity on the controller's device buses stopped.
Wide Area Network
(WAN)
A network that spans a large geographic area.
write-back cache
A cache configuration that increases the performance of host
write requests. If a host requests a write operation, the
controller writes the host's data first to the cache memory,
completing the request quickly. It performs the slower
operation of flushing data to the external storage device at a
later time. The host sees the write operation as complete when
the data reaches the cache.
For most controllers using write-back cache, the cache also
increases performance with read cache techniques.
write only
A device state that indicates that while a member was being
reconstructed an error was found on another member of the
virtual disk.
write-through cache
A technique for handling host write requests in read caches. If
the host requests a write operation, the controller writes data
directly to the external storage device and updates the cache
memory to ensure that the memory does not contain obsolete
data. This technique increases the chances that future host read
requests can be filled from the cache. The host sees the write
operation as complete only after the external storage device is
updated.
For some controller fault conditions, write-back cache resorts to
write-through cache operation to protect your data.