Gigahertz and server processors. How much is needed for happiness?

Question

Computers

Good afternoon.

It is necessary to choose a server for the enterprise, on which virtual machines will be running with:
-Domain controller;
-Mail server;
- ACS;
- Video recorder;
-Virtualka "For the Soul" (A player with music will work here to satisfy the aesthetic feelings of employees and God knows what else for the same purposes);
-An anti-virus system management console (In the requirements, it is a separate virtual machine, it can be changed).

Even though the gen. the director still ignores this task, I expect an additional virtual machine for remote access of employees to their jobs (that is, RDP up to three users at a time). Employees often need to work remotely, but now access is almost uncontrolled, which breaks many security policies.
Obviously, but it is quite possible to add new virtual machines during the operation of the server.

Details about the enterprise:
-Up to 30 users connected at a time to a corporate resource. Given the growth, the enterprise will not overcome the mark of 50 users in the next 3 years;
- Windows Server 2012 R2 was purchased for the server and it will work on most virtual machines.

Essence of the question:
How many GHz does a processor need to serve such a server?
Unfortunately, my knowledge of processors is not very deep yet and I cannot choose an adequate option for such diverse tasks. It is clear that you need a 6, and preferably an 8-core processor to keep all this in good condition, but how to estimate the required number of GHz? I ask, if possible, to explain in detail or give links to reading material, so that I can fill the gap in my knowledge.

Thank you.

UPD1:
I can calculate the need for RAM, hard drives and even processor cores. But the question is, how can you calculate the number of GHz required by the processor to perform such tasks?

Answer 1

Consider 2 G per user under RDP so that the software moves normally there. 2 G for AD, 2 G for mail, etc. - all tasks are 2 G each.
Take more cores, consider the dual-processor option. Gigahertz will squeeze you from above with a budget, take the maximum amount of money they will give.
And you forgot the very important and expensive thing about RAID - I would rely on RAID 1+0 with at least 10 working disks + 2 HOT. With so many disks, SSD or HDD is no longer important. Moreover, RAID with a battery, so that you can turn on the write cache. And it's all expensive.
After you see the total amount, you will have no problem choosing gigahertz. You choose how much money they will give to them ....

Answer 2

My friend, I have a situation similar to yours, here's how I decided: now I have two iron "servers"
One i7 3770k, 16gb, wserv2008r2 on raid1, acts as a domain controller, file sharing, and a host for two virtual machines:
1) wserv2008r2, 8GB allocated (enough for 16GB of workflow database), for 1C (1C software license is very sensitive to config changes, so you need to virtualize it 100%) I put this virtual machine on a separate raid1, otherwise 2 systems slow down.
2) winxp, 2GB, with a consultant and kasper security center, lying on a separate disk, not in a raid, since it's not scary if the disk dies
Total: i7 3770k, 16gb, 2 raid arrays each with 2 disks => 4 hard + 1 for small things
By the way, I took advice for greater fault tolerance of hard-wired ones for the host wd black, expensive, but tenacious and wd red for a virtual machine 1c. For small things I took wd green
Plus, I work on the same server, running Corel, chrome with a bunch of tabs and other crap, that is, I eat off the remaining RAM.
The second server:
centos, amd x6 1100t, 4gb one of these days we are switching to ip telephony, so I will increase the memory to 8gb, the domain controller has 2
Virtual machines on it:
1) freebsd as a gateway, 1gb
2) I am going to plug in asterisk
For an asterisk, I will buy a wd red
raid these are enough for my eyes, just to throw the RAM)