Delay in Data synchronizing to secondary replica in AlwaysOn

Hi,

I have configured SQL Server 2014 AlwaysOn setup in Asynchronous mode for database having 1.5 TB size.

After some time i found that there is 4 hrs delay in data between primary and secondary replica located across data center.

I checked in AlwaysOn DashBoard on primary replica, it is showing following information :-

Estimated Data Loss (Time) = 03:04 hrs

Log Send Queue Size (KB) = 71275013

Log Sent Rate (KB/Sec) = 4658

So Data sync delay is due to log is not transferring to secondary replica with sufficient rate.

Can anyone help me to figure out exact reason of low log sent rate ?

Mark As Answer If My Reply Is Helpful<br/> Thanks<br/> Neeraj Bhandari (MCTS - Sql Server 2008)