I have 4 ESX 4.0 hosts (a,b,c,d), 3 SATA Lefthand iSCSI SANS,1 SAS Lefthand iSCSI SAN
Hosts a,b & c can see all 3 SAS sans and the 1 SATA san
Hosts a,b,c & d can ping all 4 storage devices
Hosts a,b & c can vmkping all 4 storage devices
Why can host D ping the SATA san, but it cannot vmkping it?
Best Answer
You don't have a vmkernel port on host d that is correctly configured. It might simply be that you have incorrect settings on the port(s) or vswitch(es) or it might be an issue on the physical switch port your iSCSI uplinks from host d are connected to. Check that the correct physical nics are bound to the right things too, it might simply be that some cables have been swapped around. And it might simply be that you have dodgy cables on those iSCSI uplinks. You could have a dodgy nic on the server - it's always possible.
For ESX 3.5 and earlier you need both Service Console (ping tests this) and vmkernel (vmkping tests this) visibility to you SAN ports for iSCSI to work. With ESX 4 the Service Console requirement no longer applies but without a working vmkernel port that your iSCSI Initator can use you wont be able to get connected to the iSCSI targets.
Assuming that all four hosts are very similar a good place to start is to check that the network configuration on host d matches the pattern on the others. The CDP info bubble on vSwitch uplinks can be very useful as it will tell you a lot about the physical switch and switch port each uplink is connected to if your physical switching environment supports CDP.