Delayed ACK needs to be disabled on the ESX servers.   this KB explains how to do so.  kb.vmware.com/.../search.do Also Disabling LRO can also improve performance.  Within VMware, the following command will query the current LRO value. # esxcfg-advcfg -g /Net/TcpipDefLROEnabled To set the LRO value to zero (disabled): # esxcfg-advcfg -s 0 /Net/TcpipDefLROEnabled NOTE: a server reboot is required. Info on changing LRO in the Guest network. docwiki.cisco.com/.../Disable_LRO ESXI v5.0 should also have the Login Timeout changed to 60 seconds.  (default is 5).  However, you have to be at build 514841 or better.   See VMware KB 2007680 kb.vmware.com/.../2007680 If you are not running MEM, which requires enterprise or enterprise+ license then make sure the datastores are set to Round Robin and the IOs per path is changed from 1000 to 3.  This earlier thread has more on these.  en.community.dell.com/.../20008239.aspx Regards, 
[IMAGE] We have several arrays, some SATA and some SAS. The SAS one looks fine when using this tool but the SATA one (above) always says the array is maxed out. This would be a concern except that the IOPS for both read and write climb several times higher that the level where it first shows 100% usage. Likewise the estimated max iops is way below the level of actual iops on many occasions. I understand that this is generated by an algorithm to be used as a guide and so not perfect but in the case of this array, it's not even close. It never is. Either a) I'm reading it wrong or b) some profile for the sata array algo is not correct. Can anyone shed some light on this?  Thanks
Help me understand what this Experimental Analysis is trying to tell me