mirror of https://github.com/BOINC/boinc.git
81 lines
3.1 KiB
HTML
81 lines
3.1 KiB
HTML
<title>Compute Model: Storage</title>
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<body bgcolor=ffffff>
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<h2>Compute Model: Storage</h2>
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<h3>Files</h3>
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<p>
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The BOINC storage model is based on <b>files</b>.
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The inputs and
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outputs of applications, and the applications executables, are files.
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<p>
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A file is described by an XML element of the form
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<pre>
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<file_info>
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<name>foobar</name>
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<url>http://a.b.c/foobar</url>
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<url>http://x.y.z/foobar</url>
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...
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<md5_cksum>123123123123</md5_cksum>
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<nbytes>134423</nbytes>
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<max_nbytes>200000</max_nbytes>
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[ <executable/> ]
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[ <upload_when_present/> ]
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[ <sticky/> ]
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</file_info>
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</pre>
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The components are as follows:
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<ul>
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<li> The <b><name></b> element gives the file's name, which
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must be unique within the project.
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<li> Each <b><url></b> element gives a URL where the file is
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(or will be) located on a data server.
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<li> The <b><md5_cksum></b> element is the MD5 checksum of the
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file, providing protection against corruption and spoofing.
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<li> The <b><nbytes></b> element is the size of the file in
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bytes (may be greater than 2^32).
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<li> The <b><max_nbytes></b> element is the maximum allowable
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size of the file in bytes (may be greater than 2^32).
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This is used to prevent flooding data servers with bogus data.
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<li> The <b><sticky></b> element, if present, indicates that
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the file should be retained on the client after its initial use.
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<li> The <b><upload_when_present></b> element, if present,
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indicates that the file should be uploaded after it is created.
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<li> The <b><executable></b> element, if present, indicates
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that the file protections should be set to allow execution.
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</ul>
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These attributes allow the specification of various types of files: for
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example, input or output files that are retained for use as input to
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later computations.
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<p>
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Once a file is created (on a data server or a participant host) it
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is immutable.
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<h3>File references</h3>
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<p>
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Files may be associated with <a href="work.html">workunits</a>,
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<a href="result.html">results</a> and
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<a href="app.html">application versions</a>.
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Each such association is represented by an XML element of the form
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<pre>
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<file_ref>
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<file_name>foobar</file_name>
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[ <open_name>input</open_name> ]
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[ <fd>2</fd> ]
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[ <main_program/> ]
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</file_ref>
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</pre>
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The components are as follows:
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<ul>
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<li> The <b><file_name></b> element specifies a file.
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<li> The <b><open_name></b> element, if present, is the name by
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which the application will refer to the file (in a call to
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<b>fopen()</b>, for example).
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Note that this file will usually be a
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BOINC soft link rather than the actual file.
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<li> The <b><fd></b> element, if present, indicates the file
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descriptor number by which the application will access the file.
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This file descriptor will only be set up if the application calls the API
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function <tt>boinc_init</tt>.
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<li> The <b><main_program></b> element is used for files
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associated with application versions.
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It indicates that this file is the application's main program.
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</ul>
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