How to build a server config for the given requirements?

Question

Server equipment

Hello.
You need to roughly assemble the server config, but I don’t imagine it (config) at all :(
The server will spin 5-10 virtual machines, in each virtual machine there is a "set" of sites (WP, Wiki, ownCloud, mail web interface, mail server itself) , the number of users (for each virtual machine) is up to 10k, at the same time (let's say) 1k. The budget is not infinite of course, but the situation is such that it is better to buy a server "for growth" than to buy and understand that you need to buy another.
Tell me, please, at least approximately what should be?
Let's say 4 Intel Xeon Processor E5 v4 processors, but which ones (they are from 4 to 22 cores)? How much RAM? Disks: a mirror of 2 SSDs for the system and one SSD for each virtual machine?
PS: I'm not asking you to give me a ready-made config, but I ask you to explain at least somehow in order to imagine what computing power will be required.

Answer 1

Do you understand that 5-10 virtual machines means a difference of about two times?
Calculate the requirements of one virtual machine. If you know what the OS will be there, how much space your site and mail will take up - it happens that users have 100 megabytes of mailbox enough for six months, and sometimes 10 gigabytes will be clogged with attachments in a month.
The one who can calculate the load should count. If you don't have data, you won't count. And then it’s easier to order cloud vps, which can be easily modified without reinstalling if something happens.

Answer 2

There is no clear answer here, only recommendations.
Everything strongly depends on how densely the virtual machines / containers will be used.
In your version, I would use containers, since the density of containers and the load on the machine is minimal. You can consider different options from openvz / lxd / docker , to commercial products like proxmox / virtuozzo and probably kubernetes , but it's more for developers.
The file system is better to use ZFS, if we are not talking about commercial products (proxmox exception).
This will enable Raid, the L2 disk cache subsystem. Those can use part of the memory as a cache, then it goes like an SSD cache and already ordinary HDDs. You need to understand that it is better to buy a lot of memory and it all makes sense if there are frequent calls to the file subsystem. But it will be a better option than for each SSD virtual machine (for economic purposes)
Regarding 1000 connections at the same time, they are different and can cause different loads. As you can see, there is no clear answer here, you can only conduct tests.