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   8 <title>mod_cache_disk - Apache HTTP Server</title>
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  18 <p class="menu"><a href="../mod/">Modules</a> | <a href="../mod/quickreference.html">Directives</a> | <a href="http://wiki.apache.org/httpd/FAQ">FAQ</a> | <a href="../glossary.html">Glossary</a> | <a href="../sitemap.html">Sitemap</a></p>
  19 <p class="apache">Apache HTTP Server Version 2.5</p>
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  23 <a href="http://www.apache.org/">Apache</a> &gt; <a href="http://httpd.apache.org/">HTTP Server</a> &gt; <a href="http://httpd.apache.org/docs/">Documentation</a> &gt; <a href="../">Version 2.5</a> &gt; <a href="./">Modules</a></div>
  24 <div id="page-content">
  25 <div id="preamble"><h1>Apache Module mod_cache_disk</h1>
  26 <div class="toplang">
  27 <p><span>Available Languages: </span><a href="../en/mod/mod_cache_disk.html" title="English">&nbsp;en&nbsp;</a> |
  28 <a href="../fr/mod/mod_cache_disk.html" hreflang="fr" rel="alternate" title="Français">&nbsp;fr&nbsp;</a> |
  29 <a href="../ja/mod/mod_cache_disk.html" hreflang="ja" rel="alternate" title="Japanese">&nbsp;ja&nbsp;</a> |
  30 <a href="../ko/mod/mod_cache_disk.html" hreflang="ko" rel="alternate" title="Korean">&nbsp;ko&nbsp;</a></p>
  31 </div>
  32 <table class="module"><tr><th><a href="module-dict.html#Description">Description:</a></th><td>Disk based storage module for the HTTP caching filter.</td></tr>
  33 <tr><th><a href="module-dict.html#Status">Status:</a></th><td>Extension</td></tr>
  34 <tr><th><a href="module-dict.html#ModuleIdentifier">Module Identifier:</a></th><td>cache_disk_module</td></tr>
  35 <tr><th><a href="module-dict.html#SourceFile">Source File:</a></th><td>mod_cache_disk.c</td></tr></table>
  36 <h3>Summary</h3>
  37
  38     <p><code class="module"><a href="../mod/mod_cache_disk.html">mod_cache_disk</a></code> implements a disk based storage
  39     manager for <code class="module"><a href="../mod/mod_cache.html">mod_cache</a></code>.</p>
  40
  41     <p>The headers and bodies of cached responses are stored separately on
  42     disk, in a directory structure derived from the md5 hash of the cached
  43     URL.</p>
  44
  45     <p>Multiple content negotiated responses can be stored concurrently,
  46     however the caching of partial content is not yet supported by this
  47     module.</p>
  48
  49     <p>Atomic cache updates to both header and body files are achieved
  50     without the need for locking by storing the device and inode numbers of
  51     the body file within the header file. This has the side effect that
  52     cache entries manually moved into the cache will be ignored.</p>
  53
  54     <p>The <code class="program"><a href="../programs/htcacheclean.html">htcacheclean</a></code> tool is provided to list cached
  55     URLs, remove cached URLs, or to maintain the size of the disk cache
  56     within size and/or inode limits. The tool can be run on demand, or
  57     can be daemonized to offer continuous monitoring of directory sizes.</p>
  58
  59     <div class="note"><h3>Note:</h3>
  60       <p><code class="module"><a href="../mod/mod_cache_disk.html">mod_cache_disk</a></code> requires the services of
  61       <code class="module"><a href="../mod/mod_cache.html">mod_cache</a></code>, which must be
  62       loaded before mod_cache_disk.</p>
  63     </div>
  64     <div class="note"><h3>Note:</h3>
  65       <p><code class="module"><a href="../mod/mod_cache_disk.html">mod_cache_disk</a></code> uses the sendfile feature to
  66       serve files from the cache when supported by the platform, and
  67       when enabled with <code class="directive"><a href="../mod/core.html#enablesendfile">EnableSendfile</a></code>.
  68       However, per-directory and .htaccess configuration of
  69       <code class="directive"><a href="../mod/core.html#enablesendfile">EnableSendfile</a></code> are ignored by
  70       <code class="module"><a href="../mod/mod_cache_disk.html">mod_cache_disk</a></code> as the corresponding settings are not
  71       available to the module when a request is being served from the
  72       cache.</p>
  73     </div>
  74 </div>
  75 <div id="quickview"><h3 class="directives">Directives</h3>
  76 <ul id="toc">
  77 <li><img alt="" src="../images/down.gif" /> <a href="#cachedirlength">CacheDirLength</a></li>
  78 <li><img alt="" src="../images/down.gif" /> <a href="#cachedirlevels">CacheDirLevels</a></li>
  79 <li><img alt="" src="../images/down.gif" /> <a href="#cachemaxfilesize">CacheMaxFileSize</a></li>
  80 <li><img alt="" src="../images/down.gif" /> <a href="#cacheminfilesize">CacheMinFileSize</a></li>
  81 <li><img alt="" src="../images/down.gif" /> <a href="#cachereadsize">CacheReadSize</a></li>
  82 <li><img alt="" src="../images/down.gif" /> <a href="#cachereadtime">CacheReadTime</a></li>
  83 <li><img alt="" src="../images/down.gif" /> <a href="#cacheroot">CacheRoot</a></li>
  84 </ul>
  85 <h3>See also</h3>
  86 <ul class="seealso">
  87 <li><code class="module"><a href="../mod/mod_cache.html">mod_cache</a></code></li>
  88 <li><code class="module"><a href="../mod/mod_cache_socache.html">mod_cache_socache</a></code></li>
  89 <li><a href="../caching.html">Caching Guide</a></li>
  90 </ul><ul class="seealso"><li><a href="#comments_section">Comments</a></li></ul></div>
  91
  92 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
  93 <div class="directive-section"><h2><a name="CacheDirLength" id="CacheDirLength">CacheDirLength</a> <a name="cachedirlength" id="cachedirlength">Directive</a></h2>
  94 <table class="directive">
  95 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>The number of characters in subdirectory names</td></tr>
  96 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>CacheDirLength <var>length</var></code></td></tr>
  97 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>CacheDirLength 2</code></td></tr>
  98 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host</td></tr>
  99 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
 100 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_cache_disk</td></tr>
 101 </table>
 102     <p>The <code class="directive">CacheDirLength</code> directive sets the number
 103     of characters for each subdirectory name in the cache hierarchy. It can
 104     be used in conjunction with <code class="directive">CacheDirLevels</code> to
 105     determine the approximate structure of your cache hierarchy.</p>
 106     <p>A high value for <code class="directive">CacheDirLength</code> combined
 107     with a low value for <code class="directive">CacheDirLevels</code> will result in
 108     a relatively flat hierarchy, with a large number of subdirectories at each
 109     level.</p>
 110
 111     <div class="note">
 112       <p>The result of <code class="directive"><a href="#cachedirlevels">CacheDirLevels</a></code>* <code class="directive">CacheDirLength</code>
 113       must not be higher than 20.</p>
 114     </div>
 115
 116
 117 </div>
 118 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
 119 <div class="directive-section"><h2><a name="CacheDirLevels" id="CacheDirLevels">CacheDirLevels</a> <a name="cachedirlevels" id="cachedirlevels">Directive</a></h2>
 120 <table class="directive">
 121 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>The number of levels of subdirectories in the
 122 cache.</td></tr>
 123 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>CacheDirLevels <var>levels</var></code></td></tr>
 124 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>CacheDirLevels 2</code></td></tr>
 125 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host</td></tr>
 126 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
 127 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_cache_disk</td></tr>
 128 </table>
 129     <p>The <code class="directive">CacheDirLevels</code> directive sets the number
 130     of subdirectory levels in the cache. Cached data will be saved this
 131     many directory levels below the <code class="directive"><a href="#cacheroot">CacheRoot</a></code> directory.</p>
 132     <p>A high value for <code class="directive">CacheDirLevels</code> combined
 133     with a low value for <code class="directive">CacheDirLength</code> will result in
 134     a relatively deep hierarchy, with a small number of subdirectories at each
 135     level.</p>
 136
 137     <div class="note">
 138       <p>The result of <code class="directive">CacheDirLevels</code>*
 139       <code class="directive"><a href="#cachedirlength">CacheDirLength</a></code> must
 140       not be higher than 20.</p>
 141     </div>
 142
 143
 144 </div>
 145 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
 146 <div class="directive-section"><h2><a name="CacheMaxFileSize" id="CacheMaxFileSize">CacheMaxFileSize</a> <a name="cachemaxfilesize" id="cachemaxfilesize">Directive</a></h2>
 147 <table class="directive">
 148 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>The maximum size (in bytes) of a document to be placed in the
 149 cache</td></tr>
 150 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>CacheMaxFileSize <var>bytes</var></code></td></tr>
 151 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>CacheMaxFileSize 1000000</code></td></tr>
 152 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory, .htaccess</td></tr>
 153 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
 154 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_cache_disk</td></tr>
 155 </table>
 156     <p>The <code class="directive">CacheMaxFileSize</code> directive sets the
 157     maximum size, in bytes, for a document to be considered for storage in
 158     the cache.</p>
 159
 160     <pre class="prettyprint lang-config">
 161       CacheMaxFileSize 64000
 162     </pre>
 163
 164
 165 </div>
 166 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
 167 <div class="directive-section"><h2><a name="CacheMinFileSize" id="CacheMinFileSize">CacheMinFileSize</a> <a name="cacheminfilesize" id="cacheminfilesize">Directive</a></h2>
 168 <table class="directive">
 169 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>The minimum size (in bytes) of a document to be placed in the
 170 cache</td></tr>
 171 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>CacheMinFileSize <var>bytes</var></code></td></tr>
 172 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>CacheMinFileSize 1</code></td></tr>
 173 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory, .htaccess</td></tr>
 174 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
 175 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_cache_disk</td></tr>
 176 </table>
 177     <p>The <code class="directive">CacheMinFileSize</code> directive sets the
 178     minimum size, in bytes, for a document to be considered for storage
 179     in the cache.</p>
 180
 181     <pre class="prettyprint lang-config">
 182       CacheMinFileSize 64
 183     </pre>
 184
 185
 186 </div>
 187 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
 188 <div class="directive-section"><h2><a name="CacheReadSize" id="CacheReadSize">CacheReadSize</a> <a name="cachereadsize" id="cachereadsize">Directive</a></h2>
 189 <table class="directive">
 190 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>The minimum size (in bytes) of the document to read and be cached
 191   before sending the data downstream</td></tr>
 192 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>CacheReadSize <var>bytes</var></code></td></tr>
 193 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>CacheReadSize 0</code></td></tr>
 194 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory, .htaccess</td></tr>
 195 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
 196 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_cache_disk</td></tr>
 197 </table>
 198     <p>The <code class="directive">CacheReadSize</code> directive sets the
 199     minimum amount of data, in bytes, to be read from the backend before the
 200     data is sent to the client. The default of zero causes all data read of
 201     any size to be passed downstream to the client immediately as it arrives.
 202     Setting this to a higher value causes the disk cache to buffer at least
 203     this amount before sending the result to the client. This can improve
 204     performance when caching content from a reverse proxy.</p>
 205
 206     <p>This directive only takes effect when the data is being saved to the
 207     cache, as opposed to data being served from the cache.</p>
 208
 209     <pre class="prettyprint lang-config">
 210       CacheReadSize 102400
 211     </pre>
 212
 213
 214 </div>
 215 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
 216 <div class="directive-section"><h2><a name="CacheReadTime" id="CacheReadTime">CacheReadTime</a> <a name="cachereadtime" id="cachereadtime">Directive</a></h2>
 217 <table class="directive">
 218 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>The minimum time (in milliseconds) that should elapse while reading
 219   before data is sent downstream</td></tr>
 220 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>CacheReadTime <var>milliseconds</var></code></td></tr>
 221 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>CacheReadTime 0</code></td></tr>
 222 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory, .htaccess</td></tr>
 223 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
 224 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_cache_disk</td></tr>
 225 </table>
 226     <p>The <code class="directive">CacheReadTime</code> directive sets the minimum amount
 227     of elapsed time that should pass before making an attempt to send data
 228     downstream to the client. During the time period, data will be buffered
 229     before sending the result to the client. This can improve performance when
 230     caching content from a reverse proxy.</p>
 231
 232     <p>The default of zero disables this option.</p>
 233
 234     <p>This directive only takes effect when the data is being saved to the
 235     cache, as opposed to data being served from the cache. It is recommended
 236     that this option be used alongside the
 237     <code class="directive"><a href="#cachereadsize">CacheReadSize</a></code> directive to
 238     ensure that the server does not buffer excessively should data arrive faster
 239     than expected.</p>
 240
 241     <pre class="prettyprint lang-config">
 242       CacheReadTime 1000
 243     </pre>
 244
 245
 246 </div>
 247 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
 248 <div class="directive-section"><h2><a name="CacheRoot" id="CacheRoot">CacheRoot</a> <a name="cacheroot" id="cacheroot">Directive</a></h2>
 249 <table class="directive">
 250 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>The directory root under which cache files are
 251 stored</td></tr>
 252 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>CacheRoot <var>directory</var></code></td></tr>
 253 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host</td></tr>
 254 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
 255 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_cache_disk</td></tr>
 256 </table>
 257     <p>The <code class="directive">CacheRoot</code> directive defines the name of
 258     the directory on the disk to contain cache files. If the <code class="module"><a href="../mod/mod_cache_disk.html">mod_cache_disk</a></code> module has been loaded or compiled in to the
 259     Apache server, this directive <em>must</em> be defined. Failing to
 260     provide a value for <code class="directive">CacheRoot</code> will result in
 261     a configuration file processing error. The <code class="directive"><a href="#cachedirlevels">CacheDirLevels</a></code> and <code class="directive"><a href="#cachedirlength">CacheDirLength</a></code> directives define
 262     the structure of the directories under the specified root directory.</p>
 263
 264     <pre class="prettyprint lang-config">
 265       CacheRoot c:/cacheroot
 266     </pre>
 267
 268
 269 </div>
 270 </div>
 271 <div class="bottomlang">
 272 <p><span>Available Languages: </span><a href="../en/mod/mod_cache_disk.html" title="English">&nbsp;en&nbsp;</a> |
 273 <a href="../fr/mod/mod_cache_disk.html" hreflang="fr" rel="alternate" title="Français">&nbsp;fr&nbsp;</a> |
 274 <a href="../ja/mod/mod_cache_disk.html" hreflang="ja" rel="alternate" title="Japanese">&nbsp;ja&nbsp;</a> |
 275 <a href="../ko/mod/mod_cache_disk.html" hreflang="ko" rel="alternate" title="Korean">&nbsp;ko&nbsp;</a></p>
 276 </div><div class="top"><a href="#page-header"><img src="../images/up.gif" alt="top" /></a></div><div class="section"><h2><a id="comments_section" name="comments_section">Comments</a></h2><div class="warning"><strong>Notice:</strong><br />This is not a Q&amp;A section. Comments placed here should be pointed towards suggestions on improving the documentation or server, and may be removed again by our moderators if they are either implemented or considered invalid/off-topic. Questions on how to manage the Apache HTTP Server should be directed at either our IRC channel, #httpd, on Freenode, or sent to our <a href="http://httpd.apache.org/lists.html">mailing lists</a>.</div>
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