I'm looking a Zimbra cluster scheme installation and i thinking in the next solution:

2 Ldap Server (master and replica)
4 MailStore Servers (with SAN Connection)
2 Mta Servers
2 Zimbra AS/AV Servers

This is scheme correct?

Some questions about this scheme:

1. I need the others server are connected to a SAN or the data could be locally?
2. For MTAs, i considering separating for AS/AV servers... its ok? or can i install 4 MTAs with Zimbra AS/AV.
3. For Load Balancing... i need to install the zimbra-proxy on each servers? or can i install i dedicate zimbra-proxy (on its own server) but in this case how can i resolve the high avalability? and which services or servers are covered with zimbra-proxy?