Exchange Server Databases

Hello Everybody,

                    I need your recommendations and advises based on real world problems. I have Single exchange server 2007 SP1 installed on top of Windows Server 2003 Ent server. The Exchange Server is connected to netapp storage and its hosting 1500 mailboxes with Three Storage groups.

                                                         Each storage group is hosting single database which is named below

First Storage Group and its Database (Size 750 gb)

Second Storage Group and its database ( Size 500gb)

Third Storage Group and its Database   (Size 520 gb)

My manager says my users should have no restriction on mailbox sizes as we have storage we can assign more space if needed.

1) I want to convince my manager that we should have mailboxes quotas, how should I ? 

2) Having Large databases is advisable ?

3) We want to have redundancy like exchange cluster ? How about SCR ? 

Thanks

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