Storage Structure

Main memory – only large storage media that the CPU can access directly.

Secondary storage – extension of main memory that provides large nonvolatile storage capacity.

Magnetic disks – rigid metal or glass platters covered with magnetic recording material .

Disk surface is logically divided into tracks, which are subdivided into sectors.

The disk controller determines the logical interaction between the device and the computer.

Moving-Head Disk Mechanism

Storage Hierarchy

Storage systems organized in hierarchy.

Speed

Cost

Volatility

Caching – copying information into faster storage system;

main memory can be viewed as a last cache for secondary storage.

Storage-Device Hierarchy

Caching

Use of high-speed memory to hold recently-accessed data.

Requires a cache management policy.

Caching introduces another level in storage hierarchy.

This requires data that is simultaneously stored in more than one level to be consistent.

Migration of A From Disk to Register