HP P3410A - NetRAID 1M RAID Controller Installation And Configuration Manual page 46

Chapter 4
Read Policy
!
The three Read policies for HP NetRAID are:
Read-Ahead: This is a memory caching feature that tells the adapter to
read sequentially ahead of requested data and cache the additional data in
memory, anticipating that the additional data will be requested.
Read-Ahead supplies sequential data faster, but it is not as efficient when
accessing random data.
Normal: This policy does not use the read-ahead memory-caching feature.
This policy is efficient when most of the data reads are random.
Adaptive: Adaptive policy causes the read-ahead feature to be used if the
last two disk accesses were in sequential sectors.
For each logical drive, record the read policy in Worksheet B.
Cache Policy
!
HP NetRAID lets you choose one of two cache policies:
Cached I/O: Reads are always cached regardless of randomness. The
selected Read policy (Read-Ahead, Normal, or Adaptive) and Write policy
(Write-Through and Write-Back) always applies.
Direct I/O: First reads to a new location always come directly from the
disk. If a location is read repeatedly, then the Read policy as selected will
apply and the read data will be cached. Read data is cached only if
accessed repeatedly. With 100% randomness, nothing is cached.
For each logical drive, record the cache policy in Worksheet B.
38
Planning