Elasticsearch Index writes is really do flush() or synch() at OS level

Elastic Stack Elasticsearch
1

Hi

Can you please let me whether Elasticsearch Index writes is really do flush() or synch() at OS level

2

It is true for the transaction log.

3

Hi,

Can you please elaborate your answer, whether index writer is really do flush() or synch() at OS level.

is it pure flush? happens at the time of index writer ..

4

I meant fsync.

5

Thanks