WordPress Multisite Dashboard has become too slow

Hi,

I installed wordpress multisite on linux server I created 3000 sub blogs and looking to grow over time. I have few plugins including wp super cache. wp minify and few others. The blogs are fine from public side but in the dashboard its too slow to navigate around. I also installed Hyper-db and inserted database details. i also increased the memory but its still too slow. can some body help me please, what am doing wrong? Thanks