SQL Server Licensing: High Availability and Disaster Recovery benefits

Sriramang 

With regards to your scenario and questions, I have provided answers (based upon the videos above).

a. We have 2 Servers ,  DC1 - Server 1 - DC2  - Server 2

     We would be installing SQL server Standard in each  of them

IKe Answer: Sure this is a good starting point.

b. Each Server has 2 CPU ( Core) 

IKe Answer:  First off, let's clarify what you mean by Each Server has 2 CPU (Core).  I am going to assume that what you mean is, you have 2 x VM's... one VM on DC1 and a second VM on DC2.  Each VM you are assigning 2 vCPU's.  Hopefully this interpretation is correct.  Please clarify if not.  

So with that in mind... my recommendation is to create a VM with a minimum of 4 vCPU's.  The reason is you will have to license a minimum of 4-cores irrespective if you only start with 2 vCPU's.  (This is a SQL licensing requirement)

c.   The Servers will have real time updates 

IKe Answer:  Okee dokee, as I'm not really sure as to what you mean by this.

d.  The DC2 server has to take over the operations in case Failure at DC1.

IKe Answer:  So from the perspective of HADR that is being exemplified in the video, you will have DC1 being your Primary SQL Instance.  DC2 will be your Secondary SQL Instance.  They will be clustered together via Windows Server Failover Cluster (and as such you will need a Quorum Witness).  From there you will create a Basic Availability Group for EACH database you have on your SQL server that you want to have HADR for.  (If you were using Enterprise licensing, you would only have to create a single Availability Group).  So on the failure of DC1, DC2 would AUTOMATICALLY take over the role of Primary SQL server.

c. Could you advise us on the licensing ?

IKe Answer: Under the HADR schema, you would need 2 x SQL Standard (2-core) licenses.

d. Any additional software required for Data Replication between DC1 & DC 2

IKe Answer: As mentioned above, you will be creating a Windows Server Failover Cluster.  I would recommend reading up on the requirements of implementing.

e. Read Write application should be simultaneous at the same time always.

IKe Answer:  This would be negative.  What you are implementing here via the above videos is an HA or DR scenario.  In both cases, you will have a single Primary Instance and then multiple Secondary Instances.  The video does not go about talking above a multiple Primary SQL instance solution.  Therefore, Read/Write applications will only always go to the Primary SQL only.

f. When DC1 comes back alive, operations shall shift back to DC 1

IKe Answer:  Totally your choice.  Manual failback can be pushed out so that DC1 is always your Primary instance, and thereby causes less confusion with any troubleshooting.