title: how to configure a FileEntityStoreService
body: <p>I'm trying to use a File EntityStore and I'm having an exception at activation because of slices being zero. </p>
  
  <p>I assume it's an issue with configuration but I expected the default value to be 1.</p>
  
  <p>I narrowed down to this assembly:</p>
  
  <pre><code>import org.apache.polygene.api.common.Visibility;
  import org.apache.polygene.api.structure.Application;
  import org.apache.polygene.bootstrap.Energy4Java;
  import org.apache.polygene.entitystore.file.assembly.FileEntityStoreAssembler;
  import org.apache.polygene.index.rdf.assembly.RdfNativeSesameStoreAssembler;
  import org.apache.polygene.library.fileconfig.FileConfigurationAssembler;
  
  public class FileStoreException {
      public static void main(String[] args) throws Exception {
          Energy4Java polygene = new Energy4Java();
          Application application = polygene.newApplication(factory -&gt; factory.newApplicationAssembly(
                  module -&gt; {
                      new FileConfigurationAssembler()
                              .visibleIn(Visibility.application)
                              .assemble(module);
  
                      new FileEntityStoreAssembler()
                              .withConfig(module, Visibility.application)
                              .assemble(module);
  
                      new RdfNativeSesameStoreAssembler()
                              .withConfig(module, Visibility.application)
                              .assemble(module);
  
                      module.defaultServices();
                  })
          );
          application.activate();
      }
  }
  </code></pre>
  
  <p>The end of the stacktrace:</p>
  
  <pre><code>Caused by: java.lang.ArithmeticException: / by zero
      at method "get" of FileEntityStoreService:FileEntityStoreService in module [Module 1] of layer [Layer 1].(:0)
      at org.apache.polygene.entitystore.file.FileEntityStoreMixin.getDataFile(FileEntityStoreMixin.java:277)
      at org.apache.polygene.entitystore.file.FileEntityStoreMixin.getDataFile(FileEntityStoreMixin.java:328)
      at org.apache.polygene.entitystore.file.FileEntityStoreMixin.get(FileEntityStoreMixin.java:138)
      at org.apache.polygene.spi.entitystore.helpers.JSONMapEntityStoreMixin.entityStateOf(JSONMapEntityStoreMixin.java:193)
      ... 14 more
  </code></pre>
  
  <p>I'm using version 3.0.0 and I'm on linux.</p>