Plesk panel is loading slow (actions within him also)

[MislavO]

Hello. I know there are many topics regarding this and I've probably read most of them (including different google result/searches), but so far I'm unable to find solution for my problem. My problem is Plesk Panel, it's loading slow, usually 5-10 seconds, but sometimes 30sec - 1min.

Problem is with main plesk panell access, so for example:
- https://<SERVER_HOSTNAME>:8443 - this is loading slow
- if I try to access plesk through some domain, e.g. https://<DOMAIN_NAME_ON_THE_SERVER>:8443 - this loads almost instantly (1-2 seconds)

Please note that all websites hosted on this server are loading fast (2-3 seconds) and this issue is specific only with Plesk panel access (and actions performed in Plesk are also slow - e.g. when I'm opening new email or FTP account, that takes a while, ~ 20-30 seconds).

There are about ~ 450-500 domains hosted on this server. Since I was monitor this, extra long panel loads usually happens when I see sw-stat and awstat proccesses in "top". Although when they are not in "top", panel is also loading slow. However, there is no specific errors in logs.

Here is server configuration:
- plesk panel 11.0.9.
- running Debian 6.0.6
- Intel Core i7-2600 Quadcore (Hyper-Threading)
- RAM - 32 GB DDR3

And here is my apache configuration:

Timeout 15
KeepAlive On
MaxKeepAliveRequests 80
KeepAliveTimeout 3

<IfModule mpm_prefork_module>

StartServers 50
MinSpareServers 25
MaxSpareServers 100
MaxClients 250
MaxRequestsPerChild 1000​

</IfModule>

And finally here is fcgi configuration (using fast cgi):

FcgidProcessLifeTime 500

FcgidMaxProcesses 1500

FcgidMaxProcessesPerClass 100

FcgidMinProcessesPerClass 0

FcgidConnectTimeout 60

FcgidIOTimeout 1000

FcgidIdleScanInterval 10

FcgidIdleTimeout 60

FcgidInitialEnv RAILS_ENV production

FcgidMaxRequestsPerProcess 1500

FcgidMaxRequestLen 10737418

Usually daily load is 1-2, when there is high traffic, 4-6.

Any suggestion/critic/article is more the welcome.