The cluster is issuing too many GRS reads when attempting to obtain and maintain access to locatable resources in support of SPARQL query.
The cluster currently does excessive reads through to the GRS (Global Row Store) because the propertyCache in the DefaultLocator is defeated by the absence of the commitTime metadata for a transaction. However, the use of the readLock in the NanoSparqlServer should result in a stable txid for all query requests against that NSS instance. Therefore, we should be able to cache based on the txid and avoid most GRS reads on the cluster.
Also see  and 
 http://sourceforge.net/apps/trac/bigdata/ticket/454 (Global Row Store Read on Cluster uses Tx)
 https://sourceforge.net/apps/trac/bigdata/ticket/266 (Refactor native long tx id to thin object)