Note to my self: performance warnings

While searching for a way to quickly dump a list of VMs and their real memory usage compared to the memory granted, I stumbled upon a VMworld 2006 presentation. In it there were a few rules of thumb that will always come in handy, so I post them here. Partly for the readers of the blog, but mostly for my self :-)

Performance Warnings

Physical host CPU

  • Sustained usage of >80%
  • Unbalanced usage across cpu’s over time
  • processor queue length per cpu > 10


  • Total paging greater than 200-300 I/O per second


  • Most common area for performance issues
  • >20ms average sec/transfer time for physical disk
  • >3 average queue length
  • Split I/O average >1% of total disk I/O

Network (NIC)

  • Network queueing regularly occuring