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  10 <title>mod_cache_disk - Apache HTTP Server Version 2.5</title>
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  20 <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>
  21 <p class="apache">Apache HTTP Server Version 2.5</p>
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  25 <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>
  26 <div id="page-content">
  27 <div id="preamble"><h1>Apache Module mod_cache_disk</h1>
  28 <div class="toplang">
  29 <p><span>Available Languages: </span><a href="../en/mod/mod_cache_disk.html" title="English">&nbsp;en&nbsp;</a> |
  30 <a href="../fr/mod/mod_cache_disk.html" hreflang="fr" rel="alternate" title="Français">&nbsp;fr&nbsp;</a> |
  31 <a href="../ja/mod/mod_cache_disk.html" hreflang="ja" rel="alternate" title="Japanese">&nbsp;ja&nbsp;</a> |
  32 <a href="../ko/mod/mod_cache_disk.html" hreflang="ko" rel="alternate" title="Korean">&nbsp;ko&nbsp;</a></p>
  33 </div>
  34 <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>
  35 <tr><th><a href="module-dict.html#Status">Status:</a></th><td>Extension</td></tr>
  36 <tr><th><a href="module-dict.html#ModuleIdentifier">Module Identifier:</a></th><td>cache_disk_module</td></tr>
  37 <tr><th><a href="module-dict.html#SourceFile">Source File:</a></th><td>mod_cache_disk.c</td></tr></table>
  38 <h3>Summary</h3>
  39
  40     <p><code class="module"><a href="../mod/mod_cache_disk.html">mod_cache_disk</a></code> implements a disk based storage
  41     manager for <code class="module"><a href="../mod/mod_cache.html">mod_cache</a></code>.</p>
  42
  43     <p>The headers and bodies of cached responses are stored separately on
  44     disk, in a directory structure derived from the md5 hash of the cached
  45     URL.</p>
  46
  47     <p>Multiple content negotiated responses can be stored concurrently,
  48     however the caching of partial content is not yet supported by this
  49     module.</p>
  50
  51     <p>Atomic cache updates to both header and body files are achieved
  52     without the need for locking by storing the device and inode numbers of
  53     the body file within the header file. This has the side effect that
  54     cache entries manually moved into the cache will be ignored.</p>
  55
  56     <p>The <code class="program"><a href="../programs/htcacheclean.html">htcacheclean</a></code> tool is provided to list cached
  57     URLs, remove cached URLs, or to maintain the size of the disk cache
  58     within size and/or inode limits. The tool can be run on demand, or
  59     can be daemonized to offer continuous monitoring of directory sizes.</p>
  60
  61     <div class="note"><h3>Note:</h3>
  62       <p><code class="module"><a href="../mod/mod_cache_disk.html">mod_cache_disk</a></code> requires the services of
  63       <code class="module"><a href="../mod/mod_cache.html">mod_cache</a></code>, which must be
  64       loaded before mod_cache_disk.</p>
  65     </div>
  66     <div class="note"><h3>Note:</h3>
  67       <p><code class="module"><a href="../mod/mod_cache_disk.html">mod_cache_disk</a></code> uses the sendfile feature to
  68       serve files from the cache when supported by the platform, and
  69       when enabled with <code class="directive"><a href="../mod/core.html#enablesendfile">EnableSendfile</a></code>.
  70       However, per-directory and .htaccess configuration of
  71       <code class="directive"><a href="../mod/core.html#enablesendfile">EnableSendfile</a></code> are ignored by
  72       <code class="module"><a href="../mod/mod_cache_disk.html">mod_cache_disk</a></code> as the corresponding settings are not
  73       available to the module when a request is being served from the
  74       cache.</p>
  75     </div>
  76 </div>
  77 <div id="quickview"><h3 class="directives">Directives</h3>
  78 <ul id="toc">
  79 <li><img alt="" src="../images/down.gif" /> <a href="#cachedirlength">CacheDirLength</a></li>
  80 <li><img alt="" src="../images/down.gif" /> <a href="#cachedirlevels">CacheDirLevels</a></li>
  81 <li><img alt="" src="../images/down.gif" /> <a href="#cachemaxfilesize">CacheMaxFileSize</a></li>
  82 <li><img alt="" src="../images/down.gif" /> <a href="#cacheminfilesize">CacheMinFileSize</a></li>
  83 <li><img alt="" src="../images/down.gif" /> <a href="#cachereadsize">CacheReadSize</a></li>
  84 <li><img alt="" src="../images/down.gif" /> <a href="#cachereadtime">CacheReadTime</a></li>
  85 <li><img alt="" src="../images/down.gif" /> <a href="#cacheroot">CacheRoot</a></li>
  86 </ul>
  87 <h3>Bugfix checklist</h3><ul class="seealso"><li><a href="https://www.apache.org/dist/httpd/CHANGES_2.4">httpd changelog</a></li><li><a href="https://bz.apache.org/bugzilla/buglist.cgi?bug_status=__open__&amp;list_id=144532&amp;product=Apache%20httpd-2&amp;query_format=specific&amp;order=changeddate%20DESC%2Cpriority%2Cbug_severity&amp;component=mod_cache_disk">Known issues</a></li><li><a href="https://bz.apache.org/bugzilla/enter_bug.cgi?product=Apache%20httpd-2&amp;component=mod_cache_disk">Report a bug</a></li></ul><h3>See also</h3>
  88 <ul class="seealso">
  89 <li><code class="module"><a href="../mod/mod_cache.html">mod_cache</a></code></li>
  90 <li><code class="module"><a href="../mod/mod_cache_socache.html">mod_cache_socache</a></code></li>
  91 <li><a href="../caching.html">Caching Guide</a></li>
  92 <li><a href="#comments_section">Comments</a></li></ul></div>
  93
  94 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
  95 <div class="directive-section"><h2><a name="CacheDirLength" id="CacheDirLength">CacheDirLength</a> <a name="cachedirlength" id="cachedirlength">Directive</a> <a title="Permanent link" href="#cachedirlength" class="permalink">&para;</a></h2>
  96 <table class="directive">
  97 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>The number of characters in subdirectory names</td></tr>
  98 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>CacheDirLength <var>length</var></code></td></tr>
  99 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>CacheDirLength 2</code></td></tr>
 100 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host</td></tr>
 101 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
 102 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_cache_disk</td></tr>
 103 </table>
 104     <p>The <code class="directive">CacheDirLength</code> directive sets the number
 105     of characters for each subdirectory name in the cache hierarchy. It can
 106     be used in conjunction with <code class="directive">CacheDirLevels</code> to
 107     determine the approximate structure of your cache hierarchy.</p>
 108     <p>A high value for <code class="directive">CacheDirLength</code> combined
 109     with a low value for <code class="directive">CacheDirLevels</code> will result in
 110     a relatively flat hierarchy, with a large number of subdirectories at each
 111     level.</p>
 112
 113     <div class="note">
 114       <p>The result of <code class="directive"><a href="#cachedirlevels">CacheDirLevels</a></code>* <code class="directive">CacheDirLength</code>
 115       must not be higher than 20.</p>
 116     </div>
 117
 118
 119 </div>
 120 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
 121 <div class="directive-section"><h2><a name="CacheDirLevels" id="CacheDirLevels">CacheDirLevels</a> <a name="cachedirlevels" id="cachedirlevels">Directive</a> <a title="Permanent link" href="#cachedirlevels" class="permalink">&para;</a></h2>
 122 <table class="directive">
 123 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>The number of levels of subdirectories in the
 124 cache.</td></tr>
 125 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>CacheDirLevels <var>levels</var></code></td></tr>
 126 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>CacheDirLevels 2</code></td></tr>
 127 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host</td></tr>
 128 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
 129 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_cache_disk</td></tr>
 130 </table>
 131     <p>The <code class="directive">CacheDirLevels</code> directive sets the number
 132     of subdirectory levels in the cache. Cached data will be saved this
 133     many directory levels below the <code class="directive"><a href="#cacheroot">CacheRoot</a></code> directory.</p>
 134     <p>A high value for <code class="directive">CacheDirLevels</code> combined
 135     with a low value for <code class="directive">CacheDirLength</code> will result in
 136     a relatively deep hierarchy, with a small number of subdirectories at each
 137     level.</p>
 138
 139     <div class="note">
 140       <p>The result of <code class="directive">CacheDirLevels</code>*
 141       <code class="directive"><a href="#cachedirlength">CacheDirLength</a></code> must
 142       not be higher than 20.</p>
 143     </div>
 144
 145
 146 </div>
 147 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
 148 <div class="directive-section"><h2><a name="CacheMaxFileSize" id="CacheMaxFileSize">CacheMaxFileSize</a> <a name="cachemaxfilesize" id="cachemaxfilesize">Directive</a> <a title="Permanent link" href="#cachemaxfilesize" class="permalink">&para;</a></h2>
 149 <table class="directive">
 150 <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
 151 cache</td></tr>
 152 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>CacheMaxFileSize <var>bytes</var></code></td></tr>
 153 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>CacheMaxFileSize 1000000</code></td></tr>
 154 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory, .htaccess</td></tr>
 155 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
 156 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_cache_disk</td></tr>
 157 </table>
 158     <p>The <code class="directive">CacheMaxFileSize</code> directive sets the
 159     maximum size, in bytes, for a document to be considered for storage in
 160     the cache.</p>
 161
 162     <pre class="prettyprint lang-config">CacheMaxFileSize 64000</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> <a title="Permanent link" href="#cacheminfilesize" class="permalink">&para;</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">CacheMinFileSize 64</pre>
 182
 183
 184 </div>
 185 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
 186 <div class="directive-section"><h2><a name="CacheReadSize" id="CacheReadSize">CacheReadSize</a> <a name="cachereadsize" id="cachereadsize">Directive</a> <a title="Permanent link" href="#cachereadsize" class="permalink">&para;</a></h2>
 187 <table class="directive">
 188 <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
 189   before sending the data downstream</td></tr>
 190 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>CacheReadSize <var>bytes</var></code></td></tr>
 191 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>CacheReadSize 0</code></td></tr>
 192 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory, .htaccess</td></tr>
 193 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
 194 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_cache_disk</td></tr>
 195 </table>
 196     <p>The <code class="directive">CacheReadSize</code> directive sets the
 197     minimum amount of data, in bytes, to be read from the backend before the
 198     data is sent to the client. The default of zero causes all data read of
 199     any size to be passed downstream to the client immediately as it arrives.
 200     Setting this to a higher value causes the disk cache to buffer at least
 201     this amount before sending the result to the client. This can improve
 202     performance when caching content from a reverse proxy.</p>
 203
 204     <p>This directive only takes effect when the data is being saved to the
 205     cache, as opposed to data being served from the cache.</p>
 206
 207     <pre class="prettyprint lang-config">CacheReadSize 102400</pre>
 208
 209
 210 </div>
 211 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
 212 <div class="directive-section"><h2><a name="CacheReadTime" id="CacheReadTime">CacheReadTime</a> <a name="cachereadtime" id="cachereadtime">Directive</a> <a title="Permanent link" href="#cachereadtime" class="permalink">&para;</a></h2>
 213 <table class="directive">
 214 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>The minimum time (in milliseconds) that should elapse while reading
 215   before data is sent downstream</td></tr>
 216 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>CacheReadTime <var>milliseconds</var></code></td></tr>
 217 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>CacheReadTime 0</code></td></tr>
 218 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory, .htaccess</td></tr>
 219 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
 220 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_cache_disk</td></tr>
 221 </table>
 222     <p>The <code class="directive">CacheReadTime</code> directive sets the minimum amount
 223     of elapsed time that should pass before making an attempt to send data
 224     downstream to the client. During the time period, data will be buffered
 225     before sending the result to the client. This can improve performance when
 226     caching content from a reverse proxy.</p>
 227
 228     <p>The default of zero disables this option.</p>
 229
 230     <p>This directive only takes effect when the data is being saved to the
 231     cache, as opposed to data being served from the cache. It is recommended
 232     that this option be used alongside the
 233     <code class="directive"><a href="#cachereadsize">CacheReadSize</a></code> directive to
 234     ensure that the server does not buffer excessively should data arrive faster
 235     than expected.</p>
 236
 237     <pre class="prettyprint lang-config">CacheReadTime 1000</pre>
 238
 239
 240 </div>
 241 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
 242 <div class="directive-section"><h2><a name="CacheRoot" id="CacheRoot">CacheRoot</a> <a name="cacheroot" id="cacheroot">Directive</a> <a title="Permanent link" href="#cacheroot" class="permalink">&para;</a></h2>
 243 <table class="directive">
 244 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>The directory root under which cache files are
 245 stored</td></tr>
 246 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>CacheRoot <var>directory</var></code></td></tr>
 247 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host</td></tr>
 248 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
 249 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_cache_disk</td></tr>
 250 </table>
 251     <p>The <code class="directive">CacheRoot</code> directive defines the name of
 252     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
 253     Apache server, this directive <em>must</em> be defined. Failing to
 254     provide a value for <code class="directive">CacheRoot</code> will result in
 255     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
 256     the structure of the directories under the specified root directory.</p>
 257
 258     <pre class="prettyprint lang-config">CacheRoot c:/cacheroot</pre>
 259
 260
 261 </div>
 262 </div>
 263 <div class="bottomlang">
 264 <p><span>Available Languages: </span><a href="../en/mod/mod_cache_disk.html" title="English">&nbsp;en&nbsp;</a> |
 265 <a href="../fr/mod/mod_cache_disk.html" hreflang="fr" rel="alternate" title="Français">&nbsp;fr&nbsp;</a> |
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