MongoDB 3.0 Release Highlights and New Features

MongoDB 3.0 is officially released, bringing major updates to storage engines, backup sets, sharding clusters, and security.

The default storage engine remains MMAPv1, but collection‑level locking is added and the record allocation strategy switches to a power‑of‑2 size allocation, ignoring the former usePowerOf2Sizes flag unless noPadding is set.

A new pluggable storage engine API allows third‑party engines, and the WiredTiger engine is now supported on 64‑bit builds as an alternative to MMAPv1, requiring a change in the on‑disk format and the latest MongoDB driver.

Backup sets can now contain up to 50 members (still limited to 7 voting members). Supported drivers for large backup sets include C# (.NET) Driver 1.10, Java Driver 2.13, Python Driver (PyMongo) 3.0+, Ruby Driver 2.0+, and Node.JS Driver 2.0+. Development continues for newer driver versions, and the downgrade behavior of primary members has been modified.

Sharding enhancements: added sh.removeTagRange() to complement sh.addTagRange() and introduced a more predictive read‑preference handling where mongos re‑evaluates read preferences on each operation.

New writeConcern setting for chunk migration operations.

Improved balancer visibility; sh.status() now includes balancer status.

Security improvements include the new SCRAM‑SHA‑1 authentication mechanism and a localhost exception that restricts access to MongoDB instances.

Additional updates cover a new query introspection system, refined query output formatting, component‑specific logging categories with configurable verbosity, a complete rewrite of MongoDB tools in Go (each maintained as an independent project), and overall index and query enhancements.

Alongside MongoDB 3.0, MongoDB Ops Manager is also released, providing further operational capabilities for administrators.