Specifications

GL–24 Glossary
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.