Investigation showed that there are some inefficient server configuration settings that can cause high server load.

1) suPHP - this main part of the problem, this is most inefficient PHP configuration also known as CGI (suPHP is the same CGI with exception that every request is running under particular user ID, it adds additional level of security). With a lot of small requests it causes high load on the server, because apache has to load php entrepreneur and run separate php process each time see more small request is made. CGI is about 5x times slower than mod_php(dso) for small requests. Also opcode cache compilers do not work in such server configuration - so there is no way to even optimize it.

I understand that shared hosting has to be more secured and mod_php maybe is a bad choice, but there are some more efficient and secured configurations available, for example MPM_Prefork+SuPHP+FastCGI+eAccelerator.

2) MySQL is not optimised, enabling query cache can speedup mysql about 5x time faster, other servers where this setting enabled showed that %80 of select queries are taken from cache. Also there are many other mysql settings which can speedup MySQL server.

3) Backups are inefficient. Backup process is archiving whole system each day, it causes that up to 50% of the server resources are spending on backup during several hours. During this time sites can experience considerable slow down. I suggest to implement incremental backup solutions.

Dolphin has ways to optimize it too. We are going to implement optimisation on the whole script in 7.0.3 and in future versions.