high-availability solutions for mailbox databases

Hello,

I am New to exchange server and I want to ask you about high-availability in exchange server, how to implement Database Availability group (DAG) do we deal with these database like SQL-Database ?? are they implemented in SQL-Server Database ??

and on which server to run New-DatabaseAvailabilityGroup

don't we need windows failover cluster for the witness server ??

Regards,

Ayesh.