Hard Disk Storage and Management in Database Systems, Study Guides, Projects, Research of Introduction to Database Management Systems

Download Hard Disk Storage and Management in Database Systems and more Study Guides, Projects, Research Introduction to Database Management Systems in PDF only on Docsity! Storage and Indexes Introduction to Databases Computer Science 557 Instructor: Joe Bockhorst University of Wisconsin - Milwaukee Announcements • Any problems logging in to course accounts? • Use grid3, grid5 or weise for course work – Send bugs on weise to ceas-labstaff@uwm.edu • Reading Assignment: Chapter 14 in the textbook • Program 1 assigned today, due next Friday ca, Anatomy of a Hard Disk (a) A single-sided disk with read/write hardware. (b) A disk pack with read/write hardware. Track o | ———— Read/write Actuator Arm head Spindle Disk rotation y (b) CL > Cylinder of tracks (imaginary) <a Actuator movement Hard Drive Glossary • Disks are divided into concentric circular tracks on each disk surface. – Track capacities vary typically from ~ 4 to 50 Kbytes • The division of a track into sectors is hard-coded on the disk surface and cannot be changed • A block is an integer number of sectors – The block size B is fixed for each system. • Typical block sizes range from B=512 bytes to B=4096 bytes. – Whole blocks are transferred between disk and main memory Typical Disk Parameters Table 13.1 Specifications of Typical High-end Cheetah Disks from Seagate Description Model Number Form Factor (width) Form Factor (height) Height Width Length Weight ‘Capacity/Interface Formatted Capacity Interface Type ‘Configuration Number of disks (physical) ‘Number of heads (physical) ‘Number of Cylinders Total Tracks Bytes per Sector Areal Density ‘Track Density Kecording Density Bytes/Track (avg) Performance ‘Transfer Rates Internal Transfer Rate (min) Internal Transfer Rate (max) Formated Int. Transfer Rate (min) Formated Int. Transfer Rate (max) External I/O Transfer Rate (max) Average Formatted Transfer Rate Seek Times ‘Avg. Seek Time (Read) Avg. Seek Time (Write) Track-to-track, Seek, Read ‘Track-to-track, Seek, Write Full Dise Seek, Read Full Disc Seek, Write Average Latency Other Default Buffer (cache) size Spindle Speed Power-on to Ready Time Cheetah 10K.6 ST3146807LC 3.5 inch ch 254mm 101.6 mm 146.05 mm 0.73 Kg 146.8 Gbytes 80-pin 4 8 49,854 512 36,000 Mb/sq.inch. 64,000 Tracks/inch 570,000 bits/inch 475 Mb/sec 840 Mb/sec 43 MB/sec 78 MB/sec 320 MB/sec 59.9 MB/sec 4.7 ms (typical) 5.2 ms (typical) 0.3 ms (typical) 0.5 ms (typical) 2.99 ms 8,000 KB 10000 RPM Cheetah 10K.7 $T3300007LW 3.5 inch Linch 25.4 mm 101.6mm 146.05 mm 0.726 kg 300 Gbytes 68-pin 4 8 90,774 726,192 512 105,000 Tracks/inch 658,000 bits/inch 556 472 Mb/sec 944 Mb/sec 59 MB/sec 118 MB/sec 320 MB/sec 59.5 MB/sec 4.7 ms (typical) 5.3 ms (typical) 0.2 ms (typical) 0.5 ms (typical) 9.5 ms (typical) 10.3 ms (typical) 3 msec 8,192 KB 10000 RPM. 25 sec (Courtesy of Seagate Technology) Why not store DB in main memory? • $$$$ – cost of RAM is > 100 X hard drive cost • main memory is volatile • 32 bit addressing Managing the Hard Disk Query Optimization Relational Operators Files and Access Methods Buffer Management Disk Space Management The DSM provides an abstraction of the block as a unit of data DSM interface includes commands to read and write block commands I/O requests Operations Supported by DSM • allocate_blocks(num_blocks) – Add blocks to DB • deallocate block(blockID) – Remove block from DB • write_block(blockID, blockPtr) – Write block to disk • read_block(blockID, blockPtr) – Read block from disk allocate_blocks(3) write_block(5,data) read_block(5) deallocate block(2) Example: Managing the Hard Disk Disk Space Manager 1 yes 2 3block ID yes yesallocated? N-1 N no no 4 5 yes yes 792 793 794 * *902 903hardware addr 6 yes 7 no 904 * //allocate three consecutive blocks allocate_blocks(3) write_block(5,data) read_block(5) deallocate block(2) Example: Managing the Hard Disk Disk Space Manager 1 yes 2 3block ID yes yesallocated? N-1 N no no 4 5 yes yes 792 793 794 * *902 903hardware addr 6 yes 7 no 904 * //write blockID 5 to disk write_block(903,data) allocate_blocks(3) write_block(5,data) read_block(5) deallocate block(2) Example: Managing the Hard Disk Disk Space Manager 1 yes 2 3block ID yes yesallocated? N-1 N no no 4 5 yes yes 792 793 794 * *902 903hardware addr 6 yes 7 no 904 * // read blockID 5 to buffer read_block(903) Buffer Manager Operations • add_blocks_to_DB(num_blocks) – add new blocks to DB • delete_block_from_DB(block_id) – delete block from the DB • pin_block(block_id) – bring block from disk to buffer pool if not in BP – increment pin count for block • unpin_block(block_id) – decrement pin count for block • mark_dirty(block_id) • Buffer Manager maintains for each frame – pin count – dirty bit Buffer Manager Example buffer pool with M frames1 2 3 M-1 M - - - - - 0 0 0 0 0 no no no no no block ID pin count dirty initial state of buffer manager 1 2 3 N-1 N Buffer Manager Example buffer pool with M frames1 2 3 M-1 M 76 22 - - - 2 1 0 0 0 no no no no no block ID pin count dirty initial state of buffer manager draw on whiteboard 1 2 3 N-1 N