Our organization has been having a reoccurring problem at least once a week where our website gradually slows down until it stops responding to requests, can't SSH in, can't connect to websites, can't connect directly to MySQL database. This has been occurring for months and still haven't found the cause. We left the top command running on our webserver (CentOS 6) and connected over VMWare remote console once the server started slowing down to see if there was a specific process causing the issue (screenshot attached below).
The only other clue we noticed is that when the server starts slowing down, if we use the monitoring tools provided with VMWare ESXI we can see the disk read/write spike alot higher than average and stay really high. Only solution we've found is if we're quick enough before the server is going too slow, restart apache or mysql resolves the issue, or just rebooting the webserver. Anyone have any thoughts on possible causes?