I have a website which has a traffic of ~100k visitors a day. We are running on WordPress, and have 3 app servers with RackSpace. There are days when the servers can support ~1200 live visitors without slowing down, and on some days, the RAM usage peaks with just ~500 users and the servers crash. I have basic knowledge of system admin. How do I find out what is consuming all the RAM? I think it's a WordPress issue, rather than an Apache issue.
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If you look at /var/log/apache2/error.log you will see if apache is working right, or crashing.
Did it crash? If so then you should have a core dump - generate a stack trace from it. (I suspect it dodn't really crash).
Good metric for marketing - useless for systems admin.
All three servers "crash" simultaeneously? Highly improbable.
What is the memory usage on the OS? What is the memory usage in APC?