Which operation writes data in cache, and immediately to disk, before sending an
acknowledgement to the host?

A.
Write-through cache

B.
Write-back cache

C.
Write aside cache

D.
Write cache vaulting

Explanation:

Write Operation with Cache
Write operations with cache provide performance advantages over writing directly to disks. When
an I/O is written to cache and acknowledged, it is completed in far less time (from the host’s
perspective) than it would take to write directly to disk. Sequential writes also offer opportunities
for optimization because many smaller writes can be coalesced for larger transfers to disk drives
with the use of cache. A write operation with cache is implemented in the following ways:
•Write-back cache: Data is placed in cache and an acknowledgment is sent to the host
immediately. Later, data from several writes are committed (de-staged) to the disk. Write response
times are much faster because the write operations are isolated from the mechanical delays of the
disk. However, uncommitted data is at risk of loss if cache failures occur.
•Write-through cache: Data is placed in the cache and immediately written to the disk, and an
acknowledgment is sent to the host. Because data is committed to disk as it arrives, the risks of
data loss are low, but the write-response time is longer because of the disk operations.
EMC E10-001 Student Resource Guide. Module 4: Intelligent Storage System