Microsoft has created a very robust and expandable environment with Exchange 2010. You can add redundancy in a modular fashion. Data Availability Groups (DAG) allow more than one Exchange Mailbox server role to exist with the same data. You can also have more than one of the other roles of Exchange for added redundancy. These redundant roles can be added either now or later. There are some simple, basic configuration options that I would add if a DAG may be in your future.
Here is an interesting article on creating a high availability Exchange 2010 environment. The article does a good job of explaining what is actually going on with transaction logs and what they mean: https://tiny.cc/lpgm4