HP Array Controller HSG V8.7 Software - Manual (Page 548)

G–22 HSG80 User’s Guide
warm swap A device replacement method that allows the complete system remains
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 DIGITAL
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.
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.