MongoDB Documentation, Release 3.0.4 • All third party license notices$^{878}$. • What’s New in MongoDB 2.2 Online Conference$^{879}$. 12.2.4 Release Notes for MongoDB 2.0 Upgrading Preparation Upgrading a Standalone mongod Upgrading a Replica Set Although the major version number has changed, MongoDB 2.0 is a standard, incremental production release and works as a drop-in replacement for MongoDB 1.8. Read through all release notes before upgrading, and ensure that no changes will affect your deployment. If you create new indexes in 2.0, then downgrading to 1.8 is possible but you must reindex the new collections. mongoimport and mongoexport now correctly adhere to the CSV spec for handling CSV input/output. This may break existing import/export workflows that relied on the previous behavior. For more information see SERVER- 1097$^{880}$. Journaling (page 308) is enabled by default in 2.0 for 64-bit builds. If you still prefer to run without journaling, start mongod with the --nojournal run-time option. Otherwise, MongoDB creates journal files during startup. The first time you start mongod with journaling, you will see a delay as mongod creates new files. In addition, you may see reduced write throughput. 2.0 mongod instances are interoperable with 1.8 mongod instances; however, for best results, upgrade your deploy- ments using the following procedures: rs.stepDown() and replSetStepDown provide for shorter and more consistent failover procedures than simply shutting down the primary directly. 1. Download the v2.0.x binaries from the MongoDB Download Page$^{881}$. 2. Shutdown your mongod instance. Replace the existing binary with the 2.0.x mongod binary and restart Mon- goDB. 1. Upgrade the secondary members of the set one at a time by shutting down the mongod and replacing the 1.8 binary with the 2.0.x binary from the MongoDB Download Page$^{882}$. 2. To avoid losing the last few updates on failover you can temporarily halt your application (failover should take less than 10 seconds), or you can set write concern (page 78) in your application code to confirm that each update reaches multiple servers. 3. Use the rs.stepDown() to step down the primary to allow the normal failover (page 580) procedure. $^{878}$https://github.com/mongodb/mongo/blob/v2.2/distsrc/THIRD-PARTY-NOTICES $^{879}$http://www.mongodb.com/events/webinar/mongodb-online-conference-sept $^{880}$https://jira.mongodb.org/browse/SERVER-1097 $^{881}$http://downloads.mongodb.org/ $^{882}$http://downloads.mongodb.org/ 909 12.2. Previous Stable Releases