Today brings a new release of MongoDB. Normally I wouldn’t make a fuss about a point release, but this one has a big feature: Single server durability.

For those of you not in the know, many NoSQL databases have their own little nooks, crannies, and special cases where they diverge from what you were expecting with traditional data stores. In Mongo’s case, you had no guarantee of durability with only one instance running: you’d better have both a master as well as at least one slave if you’re doing anything in production.

You can try this out by passing a flag to mongod:

$ mongod --dur

This turns on journaling. From the documentation:

With —dur enabled, journal files will be created in a journal/ subdirectory under your chosen db path. These files are write-ahead redo logs. In addition, a last sequence number file, journal/lsn, will be created. A clean shutdown removes ll files under journal/.

In addition, 1.7.5 also brings a few other changes. You can see the changelog here.

One quick note: MongoDB uses the standard “odd numbers are development, even are stable” versioning scheme. So the 1.7.x series is still under development, and you should probably wait until the release of 1.8.x to use this feature in production unless you fully understand what you’re doing.

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