11-421-buffer_v01.pdf - Internals of a DBS I Query...

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Query Optimization And Execution Relational Operators Files and Access Methods Buffer Management Disk Space Management DB Internals of a DBS I
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The very Essentials of Disk and Buffer Management
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Cache Memory Hierarchy Magnetic tapes Magnetic disks I/O processor CPU Main memory memory Register Cache Main Memory Magnetic Disk Magnetic Tape Memory Hierarchy is to obtain the highest possible access speed while minimizing the total cost of the memory system
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4 Disks and Main Memory DBMS stores information persistently on ( hard ) disks. Unit of transfer main-memory/disk: disk blocks or pages . Time to read/write data block: 2- 10 msec for random data block (main factor is seek time) If blocks are sequentially on disk, each additional block only 1 msec Compare main memory access: in nanoseconds SSD: 0.1 ms (still slower than main memory access and calculations…) Basic operations READ: transfer data from disk to main memory (RAM). WRITE : transfer data from RAM to disk. Why disks? Cheaper than Main Memory Higher Capacity Main Memory is volatile
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Why Block/Page Concept Platters Spindle Disk head Arm movement Tracks Sector
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6 Assumed Distribution Buffer (volatile) Secondary Storage (stable)
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Trends: Faster stable storage Register Cache Main Memory Magnetic Disk Magnetic Tape Solid State Drive Solid State Drive
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8 Trends: memory databases Secondary Storage (stable)
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Later: large scale distribution
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10 Architecture Upper Layer Cache/Buffer Manager Buffer (volatile) Secondary Storage (stable)
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