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Data loss / corruption is design limitation?

• cheald 16y ago
  Yes. MongoDB doesn't ensure a write to disk before returning on an insert operation (it is what is called "eventually consistent") in order to maintain high write throughput. Because it uses memory-mapped files, it can't address anything larger than a 32-bit pointer on a 32-bit system, and so you would execute an insert, and when the DB eventually tries to write it to disk, it would fail due to lack of resources. Because the write is asynchronous, the client doesn't realize that the data has not been serialized to disk, and you end up with effective data loss. Fixing this would require either a) not using memory-mapped files, or b) ensuring full durability on writes, both of which would massively slow down the data store as a whole.