Hosting support

I have a Drupal 7.10 site with this modules:

Hello everyone,

I used to have a multisite in Drupal 7, which ran smoothly.
Now I moved to another (shared, so no SSH) server which is administered with DirectAdmin.

When applying the explanations I found on this forum, I managed to link a subdomain to it's domain with Symbolic Links in php (symlink). So test.example.com redirects to example.com. This is the code I used:

Hi, I want to upload my first drupal site on a live server. But the problem is that domain contains a raw coded php & mysql site running already and the address is like http://www.mydomain.com/index.php. Now I want to upload my drupal site (for testing) on that domain like http://www.mydomain.com/drupal_hosting(folder name containing drupal installation) without affecting the current site. Is it possible?

Thanks

I am running a dedicated server with 2gb ram based in UK with mainly UK users. A VPS with 4gb ram based in USA could be cheaper. Can anyone share experience about whether it could also be faster? Whatever I have I will probably tune it myself, though I would not mind using a service like hotdrupal where I should not need to.

Lets assume scenario of a website has approx 1 million members, .5 million posts & approx 100000 members signing at a time.. then

What should be the server requirements?
Will Drupal 7 supports these kindof huge websites? If no then what will be max limit of userbase it supports?
Is Drupal 7 supports mobile version easily?

Thanks for any help.. :)

My site has been very slow and not responding lately. I'm not sure I set it up right. I would like to have some review it and fix the issues or do the setup over. This is a paid service. Thanks.