HP StorageWorks 2000fc, Reference Manual

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Glossary 317
world wide name
(WWN) A unique 64-bit number assigned by a recognized naming authority
(often via block assignment to a manufacturer) that identifies a node
process or node port. (SNIA)
MSA2000 Family storage systems derive WWNs from the serial
numbers of controller modules and expansion modules.
world wide node
name (WWNN) A globally unique 64-bit identifier assigned to each Fibre Channel node
process. (SNIA)
world wide port name
(WWPN) A globally unique 64-bit identifier assigned to each Fibre Channel port.
(SNIA)
write policy A cache-writing strategy used to control write operations. The write
policy options are CIFS write-back and write-through cache.
write-back cache A caching technique in which the completion of a write request is
signaled as soon as the data is in cache, and actual writing to non-
volatile media occurs at a later time. Write-back cache includes an
inherent risk that an application will take some action predicated on the
write completion signal, and a system failure before the data is written
to non-volatile media will cause media contents to be inconsistent with
that subsequent action. For this reason, good write-back cache
implementations include mechanisms to preserve cache contents across
system failures (including power failures) and to flush the cache at
system restart time. (SNIA)
This is how MSA2000 Family storage systems operate. See also write-
through cache .
write-through
cache A caching technique in which the completion of a write request is not
signaled until data is safely stored on non-volatile media. Write
performance with a write-through cache is approximately that of a non-
cached system, but if the data written is also held in cache, subsequent
read performance may be dramatically improved. (SNIA)
MSA2000 Family storage systems use write-through cache when write-
back cache is disabled or when cache backup power is not working. See
also
write-back cache .