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3.10. iSCSI interface and offload support in Compute

Note
iSCSI interface and offload support is only present since Kilo.
Compute supports open-iscsi iSCSI interfaces for offload cards. Offload hardware must be present and configured on every compute node where offload is desired. Once an open-iscsi interface is configured, the iface name (iface.iscsi_ifacename) should be passed to libvirt via the iscsi_iface parameter for use. All iscsi sessions will be bound to this iSCSI interface.
Currently supported transports (iface.transport_name) are be2iscsi, bnx2i, cxgb3i, cxgb4i, qla4xxx, ocs . No configuration changes are needed outside of Compute node.
iSER is currently supported via the separate iSER LibvirtISERVolumeDriver and will be rejected if used via the iscsi_iface parameter.

3.10.1. iSCSI iface configuration
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  • Note the distinction between the transport name (iface.transport_name) and iface name (iface.iscsi_ifacename). The actual iface name must be specified via the iscsi_iface parameter to libvirt for offload to work.
  • The default name for an iscsi iface (open-iscsi parameter iface.iscsi_ifacename) is in the format transport_name.hwaddress when generated by iscsiadm.
  • iscsiadm can be used to view and generate current iface configuration. Every network interface that supports an open-iscsi transport can have one or more iscsi ifaces associated with it. If no ifaces have been configured for a network interface supported by an open-iscsi transport, this command will create a default iface configuration for that network interface. For example : 
    # iscsiadm -m iface
   default tcp,<empty>,<empty>,<empty>,<empty>
   iser iser,<empty>,<empty>,<empty>,<empty>
   bnx2i.00:05:b5:d2:a0:c2 bnx2i,00:05:b5:d2:a0:c2,5.10.10.20,<empty>,<empty>
   cxgb4i.00:07:43:28:b2:58 cxgb4i,00:07:43:28:b2:58,102.50.50.80,<empty>,<empty>
   qla4xxx.00:c0:dd:08:63:ea qla4xxx,00:c0:dd:08:63:ea,20.15.0.9,<empty>,<empty>
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    The output is in the format : iface_name transport_name,hwaddress,ipaddress,net_ifacename,initiatorname.
  • Individual iface configuration can be viewed via 
    # iscsiadm -m iface -I IFACE_NAME
   # BEGIN RECORD 2.0-873
   iface.iscsi_ifacename = cxgb4i.00:07:43:28:b2:58
   iface.net_ifacename = <empty>
   iface.ipaddress = 102.50.50.80
   iface.hwaddress = 00:07:43:28:b2:58
   iface.transport_name = cxgb4i
   iface.initiatorname = <empty>
   # END RECORD
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    Configuration can be updated as desired via 
    # iscsiadm -m iface-I IFACE_NAME--op=update -n iface.SETTING -v VALUE
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  • All iface configurations need a minimum of iface.iface_name, iface.transport_name and iface.hwaddress to be correctly configured to work. Some transports may require iface.ipaddress and iface.net_ifacename as well to bind correctly.
    Detailed configuration instructions can be found in the Linux* Open-iSCSI README file .
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