Ple nodes wring to the same le result in concurrent

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Unformatted text preview: are allow to write from their current write offsets without further token conflicts •  When mul.ple nodes are wri.ng sequen.ally to non ­overlapping sec.ons of the same file? –  Node A will relinquish only part of its byte ­range token –  Each node will be able to acquire the necessary token with a single token exchange as part of its first write opera.on CS480 Principles of Data Management Spring 2013 Negotiating byte-range token (4/4) •  Specifying the required range passed during the token nego.a.on: –  The offset –  Length of the write() system call currently being processed –  Desired range •  For future accesses •  For sequen.al access, it will be from the current write offset to infinity •  Token server revokes byte ranges only from nodes that conflict with the required range CS480 Principles of Data Management Spring 2013 Optimizing coarse-grain sharing •  Sharing happens in a large regions of the file •  GPFS predicts the region of the file being accessed by a par.cular node in the near future –  When the access paHern is predictable •  Sequen.al access •  Reverse sequen.al access •  Forward/backword strides access paHern –  Grants as large a sub ­range of the desired range as possible without conflic.ng with ranges s.ll held by other nodes CS480 Principles of Data Management Spring 2013 Optimizing fine-grain sharing (1/4) •  GPFS supports fine ­grain sharing •  Each node writes to mul.ple, smaller regions in a block •  Byte ­range tokens guarantee POSIX seman.cs and synchronized I/O to the data block of file –  Smallest unit of I/O is one sector •  Byte ­range token granularity can be no smaller than one sector –  Mul.ple nodes wri.ng in the sam...
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This note was uploaded on 02/11/2014 for the course CS 480 taught by Professor Staff during the Spring '08 term at Colorado State.

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