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I have 3 Nginx servers and each of them should handle about 2k users (concurrent connections). In front of them I have Nginx load balancer.

That's 4 Virtual machines, sharing same subnet and same physical machine. I would like to know, what VM specifications should I use for load balancer?

I have no experience with load balancing and have never done any tests, so I while I know what specs I need for my App Servers, I have no idea what should I use for nginx load balancer. Right now I'm thinking about 4 cores / 4GB RAM / 4GB HDD. What that be enough for load balancer?

Offtopic queston: Is it possible to configure mysql so that when one mysql DB is updated, so is another. Sort of like master/slave configuration or something like that?

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In order to have some redundancy and avoiding single point of failure (like the droid station was in Phantom Menace) you actually should have 2 balancers and VRRP/CARP between them. So, it's 8k connections in total. The specs you are proposing will fit. I think even 2-cored CPUs will be enough.

And I see no point creating 4 VM on one physical. When this physical node will die, so will the VMs. If we talk about a VM setup, you should use at least 2 physical nodes for 4 VMs - 2 balancers and 2 backends. If you have only one machine, using it in old-fashioned server way will do the same. It's single failure point anyway.

Mysql: Yes, it's called replication.

  • I'm not really trying to avoid single point of failure (as much as I'd like to), all I want is to distribute load to 3 different App servers, because one App server can't handle that many users. I had one simple server before and had performance issues. Thanks for the answer, I'll accept it. – CrazySabbath Nov 10 '14 at 9:26
  • There should be no performance difference in "3 VMs with application servers on one physical server" vs "one application server on one physical server". If there is, something is wrong in application server configuration. – drookie Nov 10 '14 at 11:03
  • It's not server itself, but the application and the way it's written ^^ It's a PHP/MySQL application, but it's pretty huge and resource demanding and different than any usual web PHP application. – CrazySabbath Nov 10 '14 at 13:03

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