Sql Server 2012 Failover Replica in Synchronous Mode between Primary-Secondary on VPN is very slow I have installed SQL Server 2012 Clustered HA with Replica in Sync mode between two nodes connected by an high-speed VPN. The DB is encrypted. Everything works fine, but to do the replication, the HA system takes a lot of time. 

The DB is made up of 90 tables of which only 10 are fast-moving. The average for the 10 tables is equal to 100,000 records. The others have from 1,000 to 25,000 records. Can you explain to me what is due to the slowness? 

The Primary Server how often starts the synchronization mechanism with Secondary and the Secondary how often start the same sync with Primary server (I have chosen MASTER-MASTER HA replica)?
Because you're using Synchronous replication, all transactions have to be signed off by both servers before your query can complete. You say you have a 'high speed' VPN, but, you don't make any mention of latency or bandwidth.

I suspect that you'll never be happy with the performance of synchronous replication, due to the additional latency. You should strongly consider setting the HA replication to Asynchronous.

Source: https://msdn.microsoft.com/en-us/library/ff877931.aspx