# TiFlash's Main Feature: Asynchronous Replication

![`smart`](TiFlashAsyncRep_aa_002_20220513.png)

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First of all, the Region data in TiFlash and TiKV are the same, the difference is the data format, TiFlash uses columnar storage technology.

Secondly, the Region in TiFlash joins the original Raft Group of TiKV as a Raft Learner role, forming a new Raft Group. However, the Region in TiFlash does not participate in voting or election, and does not count as a majority member. That is to say, if the Leader has written to the majority of Followers, the data can be confirmed to be written successfully without considering whether the Learner node in TiFlash has written successfully. TiFlash belongs to asynchronous replication, and has very little impact on the performance of TiKV.

Finally, TiFlash internally adopts a primary key-based fast update mechanism, making it an asynchronous replication but without too much delay from TiKV.