title: hazelcast - read-backup-data vs near cache
body: <p>In IMap configuration there is an attribute <code>read-backup-data</code> that can be set as true which enables a member to read the value from the backup copy, if available, in case the owner of the key is some other member.</p>
  
  <p><a href="http://docs.hazelcast.org/docs/latest-development/manual/html/Distributed_Data_Structures/Map/Backing_Up_Maps.html#page_Enabling+Backup+Reads" rel="nofollow noreferrer">http://docs.hazelcast.org/docs/latest-development/manual/html/Distributed_Data_Structures/Map/Backing_Up_Maps.html#page_Enabling+Backup+Reads</a></p>
  
  <p>Then there is nearcache which will start caching results for a few datastructures locally.</p>
  
  <p><a href="http://docs.hazelcast.org/docs/latest-development/manual/html/Performance/Near_Cache/Hazelcast_Data_Structures_with_Near_Cache_Support.html" rel="nofollow noreferrer">http://docs.hazelcast.org/docs/latest-development/manual/html/Performance/Near_Cache/Hazelcast_Data_Structures_with_Near_Cache_Support.html</a></p>
  
  <p>If we have 2 kinds of cluster setup:  </p>
  
  <ol>
  <li><code>2</code> members, and <code>async-backup-count</code> for a map is <code>1</code>, and <code>read-backup-data</code> is <code>true</code>  </li>
  <li><code>2</code> members, nearcache enabled for this map  </li>
  </ol>
  
  <p>Would there be differences in these 2 approaches?  </p>
  
  <p>1st setup will probably use less memory, and will not be configurable. But in terms of read performance?</p>