TAILIEUCHUNG - Lecture Database system concepts - Chapter 11: Storage and file structure

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 .

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• Database system concepts
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