We would like to build our own private cloud on Ubuntu. The services will be served via VMs are: Active directory, DNS, File serving, ERP application server, SMTP server, Continuous integration Build server, backup services and other.
Which hardware specs should be suitable for this scenario?
PS: Sorry for the generality of my question, I look for some generic ideas to start searching about!!
If you're trying to virtualize multiple services:
This is unanswerable as-is. You're only naming services, not indicating how many VM guests of what type will be needed, and how many clients they will be servicing. Imagine the same scenario without virtualization - how many hardware machines you would need will depend on the number of clients and other things that impact the expected load. Virtualization lets you consolidate so you're not wasting resources, but it doesn't reduce the load from users and internal processes.