MongoDB Documentation, Release 3.0.4 Resources 12.2.6 Release Notes for MongoDB 1.6 Upgrading Sharding Replica Sets Other Improvements • MongoDB Downloads 905 • All JIRA Issues resolved in 1.8 906 MongoDB 1.6 is a drop-in replacement for 1.4. To upgrade, simply shutdown mongod then restart with the new binaries. Please note that you should upgrade to the latest version of whichever driver you’re using. Certain drivers, including the Ruby driver, will require the upgrade, and all the drivers will provide extra features for connecting to replica sets. Sharding (page 661) is now production-ready, making MongoDB horizontally scalable, with no single point of failure. A single instance of mongod can now be upgraded to a distributed cluster with zero downtime when the need arises. • Sharding (page 661) • Deploy a Sharded Cluster (page 691) • Convert a Replica Set to a Replicated Sharded Cluster (page 699) Replica sets (page 559), which provide automated failover among a cluster of n nodes, are also now available. Please note that replica pairs are now deprecated; we strongly recommend that replica pair users upgrade to replica sets. • Replication (page 559) • Deploy a Replica Set (page 603) • Convert a Standalone to a Replica Set (page 614) • The w option (and wtimeout ) forces writes to be propagated to n servers before returning success (this works especially well with replica sets) • $or queries • Improved concurrency • $slice operator for returning subsets of arrays • 64 indexes per collection (formerly 40 indexes per collection) • 64-bit integers can now be represented in the shell using NumberLong • The findAndModify command now supports upserts. It also allows you to specify fields to return $^{905}$http://mongodb.org/downloads $^{906}$https://jira.mongodb.org/secure/IssueNavigator.jspa?mode=hide&requestId=10172 Chapter 12. Release Notes 920