Virtual Server requirements

[ov10fac]

So this is pretty much a hypothetical question. If one were to build a Virtual Server (multiple VM Guest machines) and those VMs were going to perform the following duties:

Linux File server using SAMBA and NFS (Home File server). Two to three users and about 600GB of data.
LInux Media Server using PLEX. Serving up files to mobile devices, wired PCs and smart Televisions. About 2TB of media files
Linux Domain Controller with SAMBA providing Active Directory Services for home computers, 2-3 windows computers and 2-3 Linux computers.
One or two Windows 7 / Windows 10 Virtual Machines to provide windows services for programs that will not run under linux. Nothing really complex or difficult like Office or Quick Books, just small programs that don't run well under Wine. These machines will be accessed with RDP.
One or more other VMs used to test different OS like Ubuntu, Fedora, etc.

So what kind of system would one need to do that kind of thing. Here is what I think will work.

Dell Poweredge R510 with dual XEON processors and 20 GB of ram.

Two 450GB SAS drives in a raid 1 configuration to hold the Centos 7 OS that will provide the VMs and the VMs themselves.

6 X 1TB SATA II drives that will be used for DATA only. (Ctreate DATA qcow2 files in this area as virtual drives and mount them to the VMs as necessary. These can be expanded as needed as data requirements grow)

Two external USB drives to be used as backup for the system data. Simply copy the qcow2 files to the USB drives nightly. (Something I am considering is to mount the USB drives, copy the files then unmount the drives. This should protect the data from encryption type virus. There will be two sets of drives used on alternating days.

All VM machines with 2GB of ram. (May have to up that for the Windows VMS)
Each VM will start with a minimum hard drive of about 20GB or so. Windows machines may need more.
All the linux VMs will be Centos minimal.

So, any suggestions? Am I over engineering this or under capacity? Many thanks for any ideas you might have.

[TrevorH]

Any Dell Rx10 server will be about 7 years old so you might want to review that choice before you go too far.

[ov10fac]

Yes, that's about right. In fact this particular box was purchased in July 2010 so closer to 8. If I was doing this for a client I would be doing something different, or at least a newer box. But this is just a test/hypothetical case to see how well this kind of thing works for me. I have done a little VM in the past, but nothing really in depth, so this would be a hands-on tutorial kind of thing.
Thanks for watching my back howerve.