Product manual

CDA 7 5630 Product Manual
3-2 77 A1 69UP Rev00
Data Reuse
If a given piece of information is used, there is a high probability that it will be
reused shortly thereafter.
This cache principle has been in use for years on host systems (CPU and storage
devices). The following figure illustrates this type of host cache use. The cache
used in this manner is often a high speed, high cost storage unit used as an
intermediary between the CPU and main storage.
HOST
CPU
CACHE MEMORY
Figure 3-1. Host Cache Use
3.1.1 Cache Management
In CDA 7, the channel directors and disk directors share cache. This cache
management is transparent to the host operating system. CDA 7 manages cache
using a Least Recently Used (LRU) algorithm and a Prefetch algorithm. CDA 7
dynamically switches between the LRU and Prefetch algorithms to maintain data in
cache based on the data access patterns.