Compaq StorageWorks HSG60 ACS Solution Software V8.6 for Compaq Tru64 UNIX Installation and Configuration Guide

Planning Storage 2–25
■ If you have mostly sequential reads or writes (like those needed to work with large
graphic files), then make the chunk size a small number (that is 17 sectors).
Table 2–2 shows a few examples of chunk size selection.
Increasing the Data Transfer Rate
A small chunk size relative to the average request size increases the data transfer rate
by enabling multiple disk drives to participate in one I/O request. This concept is
shown in Figure 2–16.
e
Figure 2–16. Chunk size smaller than the request size
Table 2–2 Example Chunk Sizes
Transfer Size
(KB)
Small Area of I/O
Transfers
Unknown Random Areas of I/O
Transfers
241 5979
4 79 113 163
8 157 239 317
CXO-5172A-MC
Chunk size = 128k (256 blocks)
A
1
A
4
A
2
A
3
Request A