HDD - Random access patterns

• For random access - the seek time becomes very dominant.
• Consider a disk that can read 100MB per second.
• The time for a seek could be 5 milli-seconds.
• The time to read 4KB of data will be 0.03 milli-seconds.
• even if we need to read 1MB of data - the read time will be 1 milli-second.
• Note: caching will be almost meaningless, for a system that contains 100TB of data (for instance).

Originally written by guy keren