How to avoid data loss on server failure with MongoDB on a single machine?

Question

I have read that mongoDB don't write data to disk right away, it does this periodically.

Any thoughts on how to deal with this?

Have you read the MongoDB docs? http://www.mongodb.org/display/DOCS/Journaling — Ian Mercer, Sep 26 '11 at 04:19

score 5 · Accepted Answer · answered Sep 26 '11 at 04:20

5

You can enable journaling with --journal.

Check out http://www.adathedev.co.uk/2011/03/mongodb-journaling-performance-single.html and http://www.mongodb.org/display/DOCS/Durability+and+Repair

answered Sep 26 '11 at 04:20

Dave

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From MongoDB v2.0, jounaling is enabled by default. – Chris Fulstow Sep 26 '11 at 06:19
1

Just to clarify -- journal by default enabled in 2.0 at 64 bit machines. – Andrew Orsich Sep 26 '11 at 06:51
And *only* in 64 bit machines :) – Dave Sep 26 '11 at 07:21

score 3 · Answer 2 · answered Sep 27 '11 at 15:00

Besides --journal that is enabled by default since MongoDB 2.0 (only on 64 bit machines), there is a flag that you can set when persisting data:

safe => false: do not wait for a db response
safe => true: wait for a db response
safe => num: wait for that many servers to have the write before returning
fsync => true: fsync the write to disk before returning. fsync => true implies safe=>true, but not visa versa.

If fsync=>false and safe=>true and the write could be in successfully applied to a mmapped file but not yet written to disk

How to avoid data loss on server failure with MongoDB on a single machine?

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