Shulou(Shulou.com)06/01 Report--

I. Concurrency

MMAPv1

MongoDB 3.0 provides table-level locking. Allows multiple clients to modify documents in different tables at the same time.

MongoDB 2.2-2.6 only allows concurrent reads from the same repository, but concurrent writes from the same repository are not supported.

WiredTiger

WiredTiger supports concurrent writes in the same table. Allow multiple clients to modify different rows of the same table at the same time.

II. Data consistency

Journaling

MongoDB uses journal to write to disk first. Journaling ensures that MongoDB can quickly recover log operations that have been saved to disk in the event that data modified by the MongoDB terminal is not written to the data file due to a crash or other error.

Journaling is enabled to ensure that mongod recovers data files and keeps them in a valid state in case of crash.

Read Concern

Write Concern

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