My colleague Herco van Brug wrote two great articles which can be of great help when troubleshooting ESXi 5!
The first article is from a while ago, in which Herco introduces a script which leverages the vscsistat command. This script will help you to change raw log data in some pretty exiciting graphs. More information here.
In a second, more recent, article, Herco explains how to schedule esxtop or vscsistat loging for a longer period. You can run esxtop in batch mode for a period of time, which will collect raw data from your ESXi host. Of course you can use the ESXi cron function for scheduling commands, but you will have to use some tricks to let your cron jobs survive an ESXi reboot.
A must read for everyone that’s doing ESXi troubleshooting.