Locking overhead would be unacceptable client 3 cs480

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Unformatted text preview: quent, the overhead for distributed locking may exceed the cost of forwarding requests to a central node CS480 Principles of Data Management Spring 2013 Synchronization with GPFS •  Fundamentally based on distributed locking •  Applying different techniques for different types of data –  User data vs. file metadata vs. file system metadata –  1. User data •  Byte range locking –  2. File metadata •  Dynamically elected “metanodes” for centralized management of file metadata –  3. File System metadata •  Distributed locking with centralized hints for disk space alloca.on •  Central coordinator for managing configura.on changes 5 2/1/13 CS480 Principles of Data Management 1. User Data: The Distributed Lock Manager (1/3) Spring 2013 CS480 Principles of Data Management Spring 2013 1. User Data: The Distributed Lock Manager (2/3) •  Local lock manager •  Lock tokens –  Runs on each file system node –  Convey the right to grant distributed locks •  Centralized global lock manager –  Runs on one of the nodes in the cluster –  Coordinates locks between local lock managers by handling out lock tokens •  Without separate message exchange each .me a lock is acquired or released –  Allow repeated accesses to the same disk object from the same node •  Require a single message to obtain the right to acquire a lock (lock token) on the object CS480 Principles of Data Management 1. User Data: The Distributed Lock Manager (3/3) Spring 2013 CS480 Principles of Data Management Spring 2013 1. User Data: Parallel Data Access (1/2) Client 1 •  Lock tokens – con.nued –  If an opera.on on another node requires a conflic.ng lock on the same object GPFS Coarse Grain Sharing File A Client 3 File C File B Client 2 File D File A File C File B File D •  Revoke the lock token from the first node •  Grant it to the o...
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