We have a Dell PowerEdge M710 blade server, with 144GB of RAM, with four SATA disk drives each 600GB. I could not remember the Raid level used, but the total available disk for usage is 1.63TB. We have installed ESXi 4.1 free license. After installing 10 Virtual Machines(VM) with 4GB of RAM each, and using only 6 VMs, the ESXi has become very slow. All the VMs have become extremely slow that even small software are taking huge time to install. I have heard that this may be because of Input/Output Processing and may also related to Raid. Can anyone help what might be the issue.