How to implement the organization of servers in the enterprise?

Question

Mail server

There are three physical servers:
- HP DL360p Gen8/E5-2630/8Gb/P420i 1Gb/4x450Gb SAS 10K - 2 pcs.
- HP DL320e Gen8/E1240v2/4Gb/4x500Gb SATA - 1 pc.
Basic requirements:
1) Active Directory, DNS, FileServer - all on Windows Server 2012 using HyperV
2) Postfix-based mail server
3) AD backup.
When purchasing these servers, it was assumed:
HyperV 2012 and two virtual machines with Windows Server 2012 OS will be installed on the first DL360p, AD+DNS+DHCP will be on one, and FileServer on the second.
The second physical DL360p will duplicate the first one, roughly speaking, in the evening the image will be taken from virtual machines and rolled out to the second server.
Proxmox will be installed on the HP DL320e, it will have Debian + Postfix OS, etc., only a mail server.
After some time, this scheme ceased to be as optimal as it seemed at first glance. Tell me, please, how best to organize the server infrastructure?

Answer 1

Do not breed a zoo (Proxmox+Hyper-V)
HP DL320e Gen8/E1240v2 - domain controller (AD, DNS, DHCP)
HP DL360p Gen8/E5-2630 - Hyper-V - file server, domain controller
HP DL360p Gen8/E5-2630 - Hyper-V - Debian+postfix ( habrahabr.ru/post/115630/)
Set up replication of virtual machines from one Hyper-V to another.
If you haven't bought a server yet, review the memory/disk requirements.
For backup, you need something else :-) Some kind of simple NAS, but better with alienable media.
This circuit will work fine.

Answer 2

The circuit for the decision of the task is necessary:
​​There is DC1, ess-but with a complete set of necessary network services.
Additionally raised Lync, Exchange, + additional software with integration into AD.
Do you need to additionally include DC2 in the scheme with full control of your department,
without the possibility of control and intervention from DC1,
but with shared Lync, Exchange, + additional software
with data exchange in the DC1 environment working in the department?
Trusting relationship? Or is it not so simple?