Short Answers

• Track: The disk surface is divided into several concentric circles called tracks. The thinner the tracks, the more storage capacity of the disk. Data are recorded as tiny spots on these tracks. These tracks are closed concentric circles, not a single spiral. Each track has the same number of bits although the outer tracks are longer than the inner ones.
• Sector: The circular tracks are further divided into wedge-shaped sections known as sectors. The fields of data within a particular record are organized according to tracks and sectors on a disk. - graph.

• Access time: This is an average time taken to complete the transfer of data after the request instruction has been enacted. Today's fast hard drives have access times under 10 milliseconds (ms). Access time is made up of the following four times.
• Seek Time: This is the time taken to move an access arm to a certain track on a disk after the computer requests data. Most of the access time is made up of seek time.
• Head Switching Time: The time taken for changing from one read/write head to another to read from or write on another part on a disk.
• Search Time: It is also called rotational delay time. This is a time required for the read/write head to locate particular position on a track.
• Data Transfer Time: This is the time for data to be transferred from the disk to primary storage or vice versa.

• Disk Cache: A disk cache is in a reserved segment of primary memory or in an extra memory on the disk controller card. It contains a large block of frequently accessed data copied from a disk. The data in a disk cache can be used to fulfill the following data requests from a processor in a high speed. The disk cache lets the processor avoid a slow disk access.
• Memory Cache: A memory cache is a high-speed memory storage between memory and the CPU. It is smaller and much faster than main memory (primary storage). The memory cache copies blocks of instructions and data from the main memory so that execution and data updating are performed in the higher-speed memory bank.
  

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