Server under stress

[Claudio_BZ]

I need some advice important.
My Vb forum has over 15,000 members in 12 years. The database has more than 700 Mb. For the website and the forum I have a unique server.
In August, I upgraded from VB3 to VB4. In times of many visits to the site (live sporting events), the server falls. The server returns to work only if I close the forum.
What can I do?
Sorry, I am writing with Google Translate

[final kaoss]

Read up on my article, it can definitely help (look in my sig).

If you still face problems (with mysql, ram & whatnot), you may wish to make a new thread here
https://www.vbulletin.com/forum/forumdisplay.php/14-Server-Configuration