Syncing data between onprem and Azure SQL I have the following 

Scenario: an on-premise SQL Server 2008 R2 and an app using it as db. I want to create an Azure SQL database that will be synced (asynchronous replication) with the on-premise instance. I do not want to have just a one-time migration like you can get with SQL Database Migration Wizard - (if I understand it correctly).

Goal: I need to have the on-premise instance synced, let's say via daily job that will transfer the data, with my Azure SQL database. 

Is it neccessary to setup Azure Data Factory for this? What about Data Sync? I can see that it is not available on the "new portal". Any advice how to approach this in a simple way would be great. Thanks!

EDIT: So, I have looked into the case of using transactional replication as Kin suggests. However it states only versions over SQL Server 2008. Any other ideas how to cope with this? Thanks!
No .. Azure data factory is not required. 

You can set up transactional replication from on-prem to Azure. Do not use data-sync .. its buggy and have many issues.