We are using an EMC Celerra NS-120 connected to ESX 4.0 using mostly nfs and very little iscsi. We are starting to see some issues with speed and we think it has to do with IO. How can I go about testing my IO? I would like to test it and see where I stack against other setups. Any information on how I can benchmark this to see how slow or fast we are would be great. Also to know where we should be at for good performance in vmware.