title: GeoWebCache truncates all tiles if disk quota exceeded
body: <p>I've implemented a web application using GeoServer to provide tile maps. In order to apply caching strategy, I've enabled the embedded GeoWebCache and set tiling page in a PostgreSQL database. The disk quota is set 5 MB and LFU approach to test the truncate behavior on quota limit exceeding. The problem is shown when the caching volumes are more than 5 MB and GeoWebCahe delete all tiles without regarding the "frequency_of_use" of each tile. Is this the expected behavior because I think it should remove least used tiles first. </p>
  
  <pre><code>&lt;!-- geowebcache-diskquota.xml --&gt;
  
  &lt;gwcQuotaConfiguration&gt;
    &lt;enabled&gt;true&lt;/enabled&gt;
    &lt;cacheCleanUpFrequency&gt;10&lt;/cacheCleanUpFrequency&gt;
    &lt;cacheCleanUpUnits&gt;SECONDS&lt;/cacheCleanUpUnits&gt;
    &lt;maxConcurrentCleanUps&gt;2&lt;/maxConcurrentCleanUps&gt;
    &lt;globalExpirationPolicyName&gt;LFU&lt;/globalExpirationPolicyName&gt;
    &lt;globalQuota&gt;
      &lt;value&gt;5&lt;/value&gt;
      &lt;units&gt;MiB&lt;/units&gt;
    &lt;/globalQuota&gt;
    &lt;quotaStore&gt;JDBC&lt;/quotaStore&gt;
  &lt;/gwcQuotaConfiguration&gt;
  </code></pre>
  
  <p>and the geowebcache-diskquota-jdbc.xml file:</p>
  
  <pre><code>&lt;gwcJdbcConfiguration&gt;
    &lt;dialect&gt;PostgreSQL&lt;/dialect&gt;
    &lt;JNDISource&gt;java:comp/env/jdbc/gwc&lt;/JNDISource&gt;
    &lt;connectionPool&gt;
      &lt;driver&gt;org.postgresql.Driver&lt;/driver&gt;
      &lt;url&gt;jdbc:postgresql://localhost:5432/gwc&lt;/url&gt;
      &lt;username&gt;postgres&lt;/username&gt;
      &lt;password&gt;&lt;/password&gt;
      &lt;minConnections&gt;1&lt;/minConnections&gt;
      &lt;maxConnections&gt;10&lt;/maxConnections&gt;
      &lt;connectionTimeout&gt;10000&lt;/connectionTimeout&gt;
      &lt;maxOpenPreparedStatements&gt;50&lt;/maxOpenPreparedStatements&gt;
    &lt;/connectionPool&gt;
  &lt;/gwcJdbcConfiguration&gt;
  </code></pre>