How many MT4 you can run on your VPS depends on a few things.
How many symbols are you receiving data for?
How many charts are you running on each MT4?
How many indicators on each chart?
How many EAs on each MT4?
How many open trades do your EAs concurrently manage on average?
Are your EA’s or indicators cpu intensive?
It is best to run each MT4 on a VPS as “lean” as possible. Run only exactly what is needed and nothing more. For example when using a trade copier EA such as ours (at SimpleTrader.net) that means 1 chart and 1 EA in total per MT4. Do not run a single indicator or EA you don’t have to. Hiding symbols that you know for sure you will not trade is recommended. This will save memory and cpu usage.
Memory (RAM) is very important to monitor when you have a VPS. Monitor your memory by using Windows Task Manager (shortcut CTRL-SHIFT-ESC). On the Performance tab of Windows Task Manager make sure the “Available” and “Free” fields (in Windows 2008) don’t show that you’re running too low. We consider low as being less than 150Mb in aggregate remaining. If you need more memory for your VPS inquire on an upgrade with support.
Windows Task Manager (2008)
Windows Task Manager (2012)
At FXVM.net we do sell VPS plans with more CPU cores but, we actually recommend for MT4 traders the Basic or Custom single CPU core VPS plan instead of buying the Advanced or Platinum plans for multiple CPU cores. In testing we’ve found MT4 doesn’t run as well (when virtualized) with heavily loaded or a large number of MT4 terminals running on multiple CPU core plans like in the larger Advanced or Platinum VPS plans.
In our experience, you are better to use multiple VPS’s and split your platforms between them instead of investing in a multi core server because you’ll get better performance for your investment.
Monitor your VPS CPU and memory usage with “Windows Task Manager” (shortcut CTRL-SHIFT-ESC) and when you see CPU utilization too high persistently then you should buy an additional Basic or Custom single CPU core plan VPS. Memory upgrades are available at any time for any plan. Please note if you order the Lite VPS plan this plan is designed for 1-2 modestly configured MT4 terminals maximum. A Basic plan VPS will run 2 to 4 terminals typically depending on their exact configuration.