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Vely expensive spring 2013 optimizing token protocol

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Unformatted text preview: f the inode and forwards its inode updates to the metanode: –  Periodically or –  Every .me the shared write token is revoked •  Metanode merges inode updates –  Retaining the largest file size and latest m.me values –  Opera.ons that update file size or m.me requires an exclusive inode lock CS480 Principles of Data Management Spring 2013 Shared write lock (1/2) •  On inode •  Allows concurrent writers on mul.ple nodes •  This shared write lock only conflicts with opera.ons that require the exact file size and/or m.me –  a stat() system call or a read opera.on that aHempts to read past end ­of ­file •  One of the nodes accessing the file is designated as the metanode for the file –  Only the metanode reads or writes the inode from or to disk –  Centralized approach CS480 Principles of Data Management Spring 2013 Updates to indirect blocks •  Each node independently allocates disk space for the data blocks it writes •  The new data block addresses are sent to the metanode –  Periodically or on revoca.on of a byte ­range token •  Then update the cached indirect blocks accordingly 8 2/1/13 CS480 Principles of Data Management Spring 2013 Metanode for File Metadata (1/2) •  Elected dynamically with the help of token server –  Acquires the metanode token for the file –  This first node will be the metanode •  Metanode relinquishes the token •  If there is request from another node aNer the token is relinquished •  Other nodes will get the iden.ty of this metanode –  Nega.ve reply –  New node will be the metanode Spring 2013 3. File System Metadata:Allocation map •  Records the alloca.on status (free or in ­use) of all disk blocks in the file system –  Block alloca.on file •  Collec.on of bits that represent availability of disk space •  e.g. Requires 32 bits per disk block –  For 32 possible subblocks per data block –  Linked lists for finding a free disk block or a subblock...
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