Chapter 11 probe below the higher levels as we describe various methods for implementing the data models and languages presented in preceding chapters. This chapter presents the following content: Overview of physical storage media, magnetic disks, raid, tertiary storage, storage access, file organization, organization of records in files, datadictionary storage. | Chapter 11: Storage and File Structure Rev. Aug 1, 2008 Database System Concepts, 5th Ed. ©Silberschatz, Korth and Sudarshan See for conditions on reuse Chapter 11: Storage and File Structure s Overview of Physical Storage Media s Magnetic Disks s RAID s Tertiary Storage s Storage Access s File Organization s Organization of Records in Files s DataDictionary Storage Database System Concepts 5th Edition ©Silberschatz, Korth and Sudarshan Classification of Physical Storage Media s Speed with which data can be accessed s Cost per unit of data s Reliability q data loss on power failure or system crash q physical failure of the storage device s Can differentiate storage into: q volatile storage: loses contents when power is switched off q nonvolatile storage: Contents persist even when power is switched off. Includes secondary and tertiary storage, as well as batterybacked up mainmemory. Database System Concepts 5th Edition ©Silberschatz, Korth and Sudarshan Physical Storage Media s Cache – fastest and most costly form of storage; volatile; managed by the computer system hardware q (Note: “Cache” is pronounced as “cash”) s Main memory: q fast access (10s to 100s of nanoseconds; 1 nanosecond = 10–9 seconds) q generally too small (or too expensive) to store the entire database q capacities of up to a few Gigabytes widely used currently Capacities have gone up and perbyte costs have decreased steadily and rapidly (roughly factor of 2 every 2 to 3 years) Volatile — contents of main memory are usually lost if a power failure or system crash occurs. Database System Concepts 5th Edition ©Silberschatz, Korth and Sudarshan Physical Storage Media (Cont.) s .
