iSCSI configuration details for host connections

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Follow these configuration details for iSCSI host connections.

Attach the system to Small Computer System Interface Over Internet Protocol (iSCSI) hosts by using the Ethernet ports on the systems.

Note: The system supports SAN devices that bridge iSCSI connections into a Fibre Channel network.
iSCSI connections route from hosts to the systems over the LAN. You must follow these configuration rules:
  • The system supports up to 1024 iSCSI sessions per node.
  • The system currently supports one iSCSI connection per session.
  • There is no SLP support for discovery.
  • Header and data digest support is provided only if the initiator is configured to negotiate.
  • Only one connection per session is supported.
  • Only ErrorRecoveryLevel 0 (session restart) is supported.
Note: For general Ethernet port protocol limitations, see General Ethernet port configuration details for host connections



Nodes can have four 10 Gbps onboard ports, one 1 Gbps technician port, three 25 Gbps adapters (six ports), or three 100 Gbps adapters (six ports).

For each Ethernet port on a node, multiple IPv4 address and multiple IPv6 address can be designated for iSCSI I/O.

iSCSI hosts connect to the system through the node-port IP addresses, which can be assigned to any Ethernet port that has host attach functionality enabled. On management ports, host attach functionality cannot be enabled.

During node failure, in addition to node-port IP addresses, the iSCSI name and iSCSI alias for the failed node are also transferred to the partner node. After the failed node recovers, the node-port IP address and the iSCSI name and alias are returned to the original node.
Note: The 100 Gbps adapter supports iSCSI. However, the performance is limited 25 Gbps per port.

IP requirements for iSCSI

Note: For general IP requirements, see General Ethernet port configuration details for host connections.
IP addresses are used to discover storage volumes and to use I/O to access the volumes. Node iSCSI IP addresses are also used to access a remote Internet Storage Name Service (iSNS) server, if configured.
  • Each node Ethernet port can be configured on the same subnet with the same gateway, or you can have each Ethernet port on separate subnets and use different gateways.
  • If you are configuring a system to use node Ethernet ports 1 and 2 for iSCSI I/O, ensure that the overall configuration also meets the system IP requirements that are listed previously.
  • To ensure iSCSI IP failover operations, nodes in the same I/O group must be connected to the same physical segments on the same node ports. However, you can configure node Ethernet ports in different I/O groups to use different subnets and different gateways.

You can configure iSNS to facilitate scalable configuration and management of iSCSI storage devices. Currently, you can have only one type of protocol that is used by the iSNS server at a time: either IPv4 or IPv6. For example, if you try to configure an IPv6 iSNS IP address when you already configured an IPv4 iSNS IP address, the new IPv6 IP address becomes the iSNS IP address. The old IP address can no longer be used for iSNS function.

iSCSI authentication

iSCSI supports two types of authentication through the Challenge Handshake Authentication Protocol (CHAP):
  1. One-way authentication: iSCSI target authenticating iSCSI initiators
  2. Two-way (mutual) authentication: iSCSI target authenticating iSCSI initiators, and vice versa.
Attention: With the iSCSI initiator, you can set two passwords: one for discovery and another for iSCSI session I/O. However, the system requires that both passwords for each type of authentication are the same. That is, two identical passwords for one-way CHAP, and two identical passwords for two-way CHAP that are different from those passwords for one-way CHAP.

Host mapping

Use this information for specific iSCSI host mapping information. For additional general host mapping information, see General Ethernet port configuration details for host connections.

iSCSI hosts that have a multipath driver that is installed can be moved in a nondisruptive manner. However, this capability does not include IBM AIX host attachment as it does not support multipath functions.

For more information about host mapping, see Host mapping.

iSCSI protocol supported session parameters

The following Ethernet session parameters are supported: 
initial_r2t = 1
immediate_data = 0
max_connections = 1
Max_recv_segment_data_length = 32k
max_xmit_data_length = 32k
max_burst_length = 32k
first_burst_length = 32k
default_wait_time = 2
default_retain_time = 20
max_outstanding_r2t = 1
data_pdu_inorder = 1
data_sequence_inorder = 1
error_recovery_level = 0
header_digest = CRC32C,None
data_digest = CRC32C,None
ofmarker = 0
ifmarker = 0
ofmarkint = 2048
ifmarkint = 2048