chapter11storageandfilestructure(已修改)
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【正文】 Database System Concepts, 5th Ed. Chapter 11: Storage and File Structure 169。Silberschatz, Korth and Sudarshan Database System Concepts 5th Edition, Oct 23, 2022. Chapter 11: Storage and File Structure ? Overview of Physical Storage Media ? Storage Access ? File Organization ? Organization of Records in Files ? DataDictionary Storage 169。Silberschatz, Korth and Sudarshan Database System Concepts 5th Edition, Oct 23, 2022. Overview of Physical Storage Media 物理存儲介質(zhì) ? Magic Disks 磁盤 ? RAID 磁盤陣列 ? Tertiary Storage 第三存儲 ? Storage Access 存取 ** ? File Organization 文件結(jié)構(gòu) ** ? Organization of Records in Files 記錄結(jié)構(gòu) ** ? DataDictionary Storage 數(shù)據(jù)字典 ** ? Storage Structures for ObjectOriented Databases 169。Silberschatz, Korth and Sudarshan Database System Concepts 5th Edition, Oct 23, 2022. Classification of Physical Storage Media ? Speed with which data can be accessed ? Cost per unit of data ? Reliability ? data loss on power failure or system crash ? physical failure of the storage device ? Can differentiate storage into: ? volatile storage: loses contents when power is switched off 易逝，揮發(fā) RAM ? nonvolatile storage: ? Contents persist even when power is switched off. ? Includes secondary and tertiary storage, as well as batterbacked up mainmemory. 磁盤，光盤，磁帶，閃存 169。Silberschatz, Korth and Sudarshan Database System Concepts 5th Edition, Oct 23, 2022. Physical Storage Media ? Cache – fastest and most costly form of storage。 volatile。 managed by the puter system hardware. 快， 易逝， 硬件 ?高速高價 ?設(shè)備 ?低速低價 ?設(shè)備 ?多種 Cache： ?CPU與內(nèi)存 ?內(nèi)存與磁盤 ?OS與 DBMS 169。Silberschatz, Korth and Sudarshan Database System Concepts 5th Edition, Oct 23, 2022. Physical Storage Media ? Main memory: 主存儲 ? fast access (10s to 100s of nanoseconds。 1 nanosecond = 10–9 seconds) 10納秒 ? generally too small (or too expensive) to store the entire database 不能存整個 DB ? 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 ， 169。Silberschatz, Korth and Sudarshan Database System Concepts 5th Edition, Oct 23, 2022. Physical Storage Media (Cont.) ? Flash memory 閃存 ? Data survives power failure 非易逝 ? Data can be written at a location only once, but location can be erased and written to again 可重寫 ? 有限次讀寫 目前質(zhì)量： 110萬次，夠用了 ? Reads are roughly as fast as main memory 讀快
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