Al io scienc compung digital media 1mb to 4mb relaonal

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Unformatted text preview: ss mul.ple disks and disk controllers •  Implements striping in the file system –  Controls fault tolerance –  Balances load across adapters, storage controllers and disks –  Does not rely on a separate logical volume management layer •  No adequate knowledge of topology to balance load •  Limited address space for the logical unit number CS480 Principles of Data Management Spring 2013 Data Striping and allocation (3/6) CS480 Principles of Data Management Spring 2013 Data Striping and allocation (2/6) •  Large files in GPFS are –  Divided into equal sized blocks –  Allocated on different disks in a round ­robin fashion •  Block size –  The largest sized I/O that GPFS can issue to the underlying device –  16KB ~ 4 MB (default: 256KB) •  Minimize seek overhead –  Large amount of data is retrieved in a single I/O from each disk CS480 Principles of Data Management Spring 2013 Data Striping and allocation (4/6) •  Small file and the last block from a large file –  Sub ­block IO Type Applica8on Examples Large Sequen.al IO Scien.fic Compu.ng, Digital Media 1MB to 4MB Rela.onal Database DB2, Oracle 512 KB Small I/O General File Service, File based 256 KB Analy.cs, Email, Web Applica.ons Special Proprietary •  The smallest alloca.on to a single file •  1/32 of the size of a full block Block Size –  If you use a block size of 1MB •  Each file will use at least 32KB (1024 KB/32 = 32KB) •  There are very few workloads that benefit from a file system with special block sizes (16 ~ 64 KB) 16 ~ 64 KB –  Op.mize your usage paHern or use default size (256KB) From: hHp://www.ibm.com/developerworks/wikis/display/hpccentral/File+System+Planning CS480 Principles of Data Management Spring 2013 Data Striping and allocation (5/6) •  Prefetching data –  Reading a large file from a single ­threaded applica.on –  Prefetches data into its buffer pool –  Issues I/...
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