On status free or inuse of all disk blocks in the le

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Unformatted text preview: e data block will cause token conflicts even if individual write opera.ons do not overlap. (“false sharing”) –  Token state and corresponding message traffic will grow CS480 Principles of Data Management Spring 2013 Optimizing fine-grain sharing (2/4) •  Data Shipping mode –  Op.mizes fine ­grain sharing for applica.ons that do not require POSIX seman.cs –  Disables normal byte ­range locking –  File blocks are assigned to nodes in a round ­robin fashion –  Each data block will be read or wriHen only by one par.cular node 7 2/1/13 CS480 Principles of Data Management Spring 2013 Optimizing fine-grain sharing (3/4) •  Data Shipping mode – con:nued –  GPFS forwards read and write opera.ons origina.ng from other nodes to the node responsible for the par.cular data block –  Requires fewer messages than a token exchange CS480 Principles of Data Management Spring 2013 Optimizing fine-grain sharing (4/4) •  Data shipping mode is primarily used by the MPI/IO library –  MPI/IO does not require POSIX seman.cs –  MPI/IO library provides a natural mechanism to define and assign blocks to nodes –  Avoids the overhead of flushing dirty data to disk when revoking a token CS480 Principles of Data Management Spring 2013 2. File Metadata: Synchronizing Access •  GPFS uses inodes and indirect blocks to store file aHributes and data block addresses •  Mul.ple nodes wri.ng to the same file result in concurrent updates to the inode and indirect blocks of the file –  To change file size and modifica.on .me (m.me) and to store the addresses of newly allocated data blocks •  Update via exclusive write locks on the inode will result in a lock conflict on every write opera.on CS480 Principles of Data Management Spring 2013 Shared write lock (2/2) •  Each writer maintains a locally cached copy o...
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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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