AEM comes with Oak storage. Oak(Apache Jackrabbit Product) is a new JCR implementation with a completely new internal architecture.
There are two options for the AEM persistence layer back-end used by Oak : TarMK and MongoMK.
Main differences b/w TarMK and MongoMK
Adobe recommendation says we must consider MongoMK when we come across below metrics
- Number of named users connected in a day: in the thousands or more.
- Number of concurrent users: in the hundreds or more.
- Volume of asset ingestion per day: in hundreds of thousands or more.
- Volume of page edits per day: in hundreds of thousands or more (including automated updates via Multi Site Manager or news feed ingestion for example).
- Volume of searches per day: in tens of thousands or more.
TarMK is optimized for single node performance whereas MongoMK is designed for scalability and clustered deployments also volume of data.