A big question for me.

Now: zimbra server 6.0.8 OSE, 40000 accounts, all in one server, one domain

Want: add second mailbox server and move accounts across this two servers to distribute high server loading.
Also upgrade all to zimbra 8.0.0 OSE.

Read a lot of documentation already but there are many questions. Take me please short manual by steps (eq. 1, 2, 3).
Or may be give another deployment schema. Thanks.

P.S. I want to create 3 servers: 1) ldap+mta, 2) and 3) mailboxes with accounts of one domain