title: org.apache.ignite.IgniteCheckedException: Cannot enable write-through
body: <p>Here is the configuration for the cache. I want writeThrough to be enabled. why i got the below exception? what does "writer or store is not provided" mean?</p>
  
  <p>Configuration:</p>
  
  <pre><code>&lt;property name="cacheConfiguration"&gt;
     &lt;bean class="org.apache.ignite.configuration.CacheConfiguration"&gt;
        &lt;property name="name" value="txnCache"/&gt;
        &lt;property name="cacheMode" value="PARTITIONED"/&gt;
        &lt;property name="writeSynchronizationMode" value="FULL_SYNC"/&gt;
        &lt;property name="writeThrough" value="true"/&gt;
        &lt;property name="backups" value="1"/&gt;
    &lt;!--property name="cacheMode" value="REPLICATED"/--&gt;
    &lt;!-- &lt;property name="atomicityMode" value="ATOMIC"/&gt;
    &lt;property name="readFromBackup" value="true"/&gt;
    &lt;property name="copyOnRead" value="true"/&gt;--&gt;
    &lt;/bean&gt;
  &lt;/property&gt;
  </code></pre>
  
  <p>Error:</p>
  
  <pre><code>[13:24:07,176][SEVERE][main][IgniteKernal] Got exception while starting (will rollback startup routine).
  class org.apache.ignite.IgniteCheckedException: Cannot enable write-through (writer or store is not provided) for cache: txnCache
          at org.apache.ignite.internal.processors.cache.GridCacheProcessor.validate(GridCacheProcessor.java:482)
          at org.apache.ignite.internal.processors.cache.GridCacheProcessor.createCache(GridCacheProcessor.java:1462)
          at org.apache.ignite.internal.processors.cache.GridCacheProcessor.onKernalStart(GridCacheProcessor.java:885)
          at org.apache.ignite.internal.IgniteKernal.start(IgniteKernal.java:1013)
          at org.apache.ignite.internal.IgnitionEx$IgniteNamedInstance.start0(IgnitionEx.java:1895)
          at org.apache.ignite.internal.IgnitionEx$IgniteNamedInstance.start(IgnitionEx.java:1647)
          at org.apache.ignite.internal.IgnitionEx.start0(IgnitionEx.java:1075)
          at org.apache.ignite.internal.IgnitionEx.start(IgnitionEx.java:573)
          at org.apache.ignite.internal.processors.platform.PlatformAbstractBootstrap.start(PlatformAbstractBootstrap.java:48)
          at org.apache.ignite.internal.processors.platform.PlatformIgnition.start(PlatformIgnition.java:76)
  [13:24:07] Cancelled rebalancing from all nodes [topology=null]
  [13:24:07] Cancelled rebalancing from all nodes [topology=null]
  </code></pre>