Enterprise Vault 10 and Exchange 2010 Environment

We are planning to have 1 EV site with 4 EV servers in order to Archive more than 13000 mailboxes in our Exchange 2010 environment. Our Exchange environment consists of 2 Mailbox servers and the plan of EV servers which i am thinking of putting in place is given below:

1. SQL cluster creation to make the environment high available with EVServer A and EVServer B and create one single database on it for the whole EV environment. Create EV Cluster on the same two servers EVServer A and EVServer B and run Archiving and Indexing on it and Mailbox Archiving Task will run to Archive databases on Mailbox server 1.
2. Create another EV Cluster and run Archiving and Indexing that will be enable on EVServer C and EVServer D, and Mailbox Archiving Task will run to Archive databases on Mailbox server 2. For Database request will go to SQL Cluster running on EVServer A and EVServer B.

The reason for taking this approach was to distribute the load of archiving 6500 mailboxes on each cluster and made it high available too.

Please advise whether the approach i am having is correct or any other suggestion in building our new EV environment will be greatly appreciated.

Thanks