Since iSCSI is a great choice as a SR for your XenServer, in terms of performance and scalability, I've decided to created a straight forward and easy to understand guide of how to connect NetApp iSCSI based storage to XenServer, read on...
On the NetApp side:
3) Dedicate a separate NIC for iSCSI traffic, be sure the filer iSCSI dedicated NIC is assigned with a proper IP address:
4)From the XenServer copy it's iscsi FQN:
5)Add the new initiator:
6)Map the new LUN to the new initiator:
On the XenServer side:
1) Be sure you have a NIC assigned to iSCSI traffic.
Click on Discover IQNs, it should find the NetApp IQN.
Next, click on Discover LUN's, it should find the available LUN's.
Click "Finish" to attach the SR.
Your newly created LUN should be successfully attached to XenServer at this point.