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MongoDB safe and fsync Explained

Kristina Chodorow explains the MongoDB safe and fsync options:

safe and fsync are not the same, here’s a rundown of the options:

  • 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.

Related to MongoDB durability.

Original title and link for this post: MongoDB safe and fsync Explained (published on the NoSQL blog: myNoSQL)