21.11. Configuring iSCSI Offload and Interface Binding
This chapter describes how to set up iSCSI interfaces in order to bind a session to a NIC port when using software iSCSI. It also describes how to set up interfaces for use with network devices that support offloading; namely, devices from Chelsio, Broadcom and ServerEngines.
The network subsystem can be configured to determine the path/NIC that iSCSI interfaces should use for binding. For example, if portals and NICs are set up on different subnets, then it is not necessary to manually configure iSCSI interfaces for binding.
Before attempting to configure an iSCSI interface for binding, run the following command first:
ping -I eth
ping fails, then you will not be able to bind a session to a NIC. If this is the case, check the network settings first.
21.11.1. Viewing Available iface Configurations
Red Hat Enterprise Linux 5.5 supports iSCSI offload and interface binding for the following iSCSI initiator implementations:
Software iSCSI — like the
ib_iser modules, this stack allocates an iSCSI host instance (i.e.
scsi_host) per session, with a single connection per session. As a result,
/proc/scsi will report a
scsi_host for each connection/session you are logged into.
Offload iSCSI — like the Chelsio
bnx2i and ServerEngines
be2iscsi modules, this stack allocates a
scsi_host for each PCI device. As such, each port on a host bus adapter will show up as a different PCI device, with a different
scsi_host per HBA port.
To manage both types of initiator implementations,
iscsiadm uses the
iface structure. With this structure, an
iface configuration must be entered in
/var/lib/iscsi/ifaces for each HBA port, software iSCSI, or network device (
eth) used to bind sessions.
To view available
iface configurations, run
iscsiadm -m iface. This will display
iface information in the following format:
Refer to the following table for an explanation of each value/setting.
Table 21.2. iface Settings
iface configuration name.
|Name of driver
|IP address to use for this port
|Name used for the
vlan or alias binding of a software iSCSI session. For iSCSI offloads,
net_iface_name will be
<empty> because this value is not persistent across reboots.
|This setting is used to override a default name for the initiator, which is defined in
The following is a sample output of the
iscsiadm -m iface command:
For software iSCSI, each
iface configuration must have a unique name (with less than 65 characters). The
iface_name for network devices that support offloading appears in the format
For example, the sample output of
iscsiadm -m iface on a system using a Chelsio network card might appear as:
It is also possible to display the settings of a specific
iface configuration in a more friendly way. To do so, use the option
-I . This will display the settings in the following format:
Using the previous example, the
iface settings of the same Chelsio video card (i.e.
iscsiadm -m iface -I cxgb3i.00:07:43:05:97:07) would appear as:
# BEGIN RECORD 2.0-871
iface.iscsi_ifacename = cxgb3i.00:07:43:05:97:07
iface.net_ifacename = <empty>
iface.ipaddress = <empty>
iface.hwaddress = 00:07:43:05:97:07
iface.transport_name = cxgb3i
iface.initiatorname = <empty>
# END RECORD