High performance I/O

There are four factors that influence I/O performance:

Data

-- Data is high volume, maybe continuous and may require contiguous storage. Direct relationship between size of data and how long it takes to handle. Compression and also distributed storage (See RAID technology (Section 5.5.3 below).

Data Storage

-- The strategy for data storage depends of the storage hardware and the nature of the data. The following storage parameters affect how data is stored:

• Storage Capacity
• Read and Write Operations of hardware
• Unit of transfer of Read and Write
• Physical organisation of storage units
• Read/Write heads, Cylinders per disk, Tracks per cylinder, Sectors per Track
• Read time
• Seek time

Data Transfer

-- Depend how data generated and written to disk, and in what sequence it needs to retrieved. Writing/Generation of Multimedia data is usually sequential e.g. streaming digital audio/video direct to disk. Individual data (e.g. audio/video file) usually streamed.

RAID architecture can be employed to accomplish high I/O rates by exploiting parallel disk access (Section 5.5.3)

Operating System Support

-- Scheduling of processes when I/O is initiated. Time critical operations can adopt special procedures. Direct disk transfer operations free up CPU/Operating system space.