Difference between revisions of "Configuration Considerations (ESX)"

| '''Round Robin IOPS''' - The number of IOs that an ESX will use a path for, before switching to an alternate path, in order to balance the load.

| (So in this instance IOPS means IO operations rather than IOs per second as it normally means).

Whether or not to change this is a contentious issue.  The ''out of the box'' default is 1000 IOs per path. HP state that when using their EVA storage systems you should set IOPS to 1 <ref>HP EVA IOPS to 1 - http://h20195.www2.hp.com/V2/GetDocument.aspx?docname=4AA1-2185ENW&cc=us&lc=en</ref>, and some other vendors appear to use IOPS=1 in their own testing. My personal feeling is to never change any setting from the default unless you have good reason to. The more you change, the more you move away from an expected configuration, and the more chance you have of exposing unexpected flaws and bugs, and the less chance a VMware support guy or gal will have of being able to help to resolve your problem quickly.

I'm not convinced that the results show a significant improvement in performance by changing the value, and where they do, you need to remember that these are isolated tests and needn't be representative of what you'd experience in your environment.  Increasing the rate of path switching increases ESX CPU usage (albeit to a small degree), so will be at the detriment of other performance metrics. So would I would not change the setting as part of a default ESX build configuration, but if experiencing storage performance problems its worth considering.

References and further reading...