ch11 - Database System Concepts, 5th Ed . ©Silberschatz,...

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Unformatted text preview: Database System Concepts, 5th Ed . ©Silberschatz, Korth and Sudarshan See www.db-book.com for conditions on re-use Chapter 11: Storage and File Structure Chapter 11: Storage and File Structure Rev. Aug 1, 2006 ©Silberschatz, Korth and Sudarshan 11.2 atabase System Concepts - 5 th Edition Chapter 11: Storage and File Structure Chapter 11: Storage and File Structure ¡ Overview of Physical Storage Media ¡ Magnetic Disks ¡ RAID ¡ Tertiary Storage ¡ Storage Access ¡ File Organization ¡ Organization of Records in Files ¡ Data-Dictionary Storage ©Silberschatz, Korth and Sudarshan 11.3 atabase System Concepts - 5 th Edition Classification of Physical Storage Media Classification of Physical Storage Media ¡ Speed with which data can be accessed ¡ Cost per unit of data ¡ Reliability z data loss on power failure or system crash z physical failure of the storage device ¡ Can differentiate storage into: z volatile storage : loses contents when power is switched off z non-volatile storage : ¡ Contents persist even when power is switched off. ¡ Includes secondary and tertiary storage, as well as battery-backed up main-memory. ©Silberschatz, Korth and Sudarshan 11.4 atabase System Concepts - 5 th Edition Physical Storage Media Physical Storage Media ¡ Cache – fastest and most costly form of storage; volatile; managed by the computer system hardware z (Note: “Cache” is pronounced as “cash”) ¡ Main memory : z fast access (10s to 100s of nanoseconds; 1 nanosecond = 10 –9 seconds) z generally too small (or too expensive) to store the entire database ¡ capacities of up to a few Gigabytes widely used currently ¡ Capacities have gone up and per-byte costs have decreased steadily and rapidly (roughly factor of 2 every 2 to 3 years) z Volatile — contents of main memory are usually lost if a power failure or system crash occurs. ©Silberschatz, Korth and Sudarshan 11.5 atabase System Concepts - 5 th Edition Physical Storage Media (Cont.) Physical Storage Media (Cont.) ¡ Flash memory z Data survives power failure z Data can be written at a location only once, but location can be erased and written to again ¡ Can support only a limited number (10K – 1M) of write/erase cycles. ¡ Erasing of memory has to be done to an entire bank of memory z Reads are roughly as fast as main memory z But writes are slow (few microseconds), erase is slower z NOR Flash ¡ Fast reads, very slow erase, lower capacity ¡ Used to store program code in many embedded devices z NAND Flash ¡ Page-at-a-time read/write, multi-page erase ¡ High capacity (several GB) ¡ Widely used as data storage mechanism in portable devices ©Silberschatz, Korth and Sudarshan 11.6 atabase System Concepts - 5 th Edition Physical Storage Media (Cont.) Physical Storage Media (Cont.) ¡ Magnetic-disk z Data is stored on spinning disk, and read/written magnetically z Primary medium for the long-term storage of data; typically stores entire database....
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This note was uploaded on 03/30/2012 for the course CSE CS317 taught by Professor Profsudarshan during the Spring '08 term at IIT Bombay.

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ch11 - Database System Concepts, 5th Ed . ©Silberschatz,...

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