After upgrading from 5.0.6 to 5.0.9 we are experiencing very slow performance when users access there calendar. After reviewing the output from iostat, top, etc, it looks like the servers overall load is light. And tailing the mailbox log indicates that the server receives the request immediately, but waits almost 15 seconds before processing. I have 2 1.6 dual core zeons, 3gb RAM, and 200gb storage. It is built on a RAID 5 but iostat shows that iowait never goes about %1.2 and 30min load averages .8 to 1.0. Any thoughts?