Disable unneccessary ohai plugins to compact the chef node size so as to speed up chef get/search API calls.
Refer to http://engineering.voxer.com/2013/03/22/chef-part-2-performance/ and https://wiki.opscode.com/display/chef/Disabling+Ohai+Plugins
Set log_level of chef-client 11 to :info explicitly instead of unset in chef 11.12.8. When not set in client.rb, INFO level log is not printed.