iSCSI configuration rules

You must follow the SAN Volume Controller configuration rules for iSCSI host connections.

You can attach the SAN Volume Controller to Small Computer System Interface Over Internet Protocol (iSCSI) hosts using the SAN Volume Controller's Ethernet ports.

Note: SAN Volume Controller supports SAN devices that bridge iSCSI connections into a fibre-channel network.
iSCSI connections route from hosts to the SAN Volume Controller over the LAN. You must follow the SAN Volume Controller configuration rules for iSCSI host connections:
  • SAN Volume Controller supports up to 256 iSCSI sessions per node
  • SAN Volume Controller currently supports one iSCSI connection per session
  • SAN Volume Controller port limits are now shared between fibre-channel WWPNs and iSCSI names

Each SAN Volume Controller node has two Ethernet ports. For each Ethernet port, a maximum of one IPv4 address and one IPv6 address can be designated for iSCSI I/O.

iSCSI hosts connect to the SAN Volume Controller through the node-port IP address. If the node fails, the address becomes unavailable and the host loses communication with SAN Volume Controller. To allow hosts to maintain access to data, the node-port IP addresses for the failed node are transferred to the partner node in the I/O group. The partner node handles requests for both its own node-port IP addresses and also for node-port IP addresses on the failed node. This process is known as node-port IP failover. 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.

Multiple configurations are supported. You can have both node Ethernet ports on the same subnet, or you can have each Ethernet port on separate subnets and use different gateways. Before you configure the Ethernet ports on separate subnets, validate that the IP configuration is correct by pinging from the iSCSI host to the nodes, and vice versa.

A SAN Volume Controller VDisk can be mapped the same way either to a fibre-channel host, an iSCSI host, or both.

Each I/O group can map VDisks to the same total maximum number of host objects (256), which could include fibre-channel attachments, iSCSI attachments, or both.

SAN Volume Controller supports the following I/O descriptions:
  • I/O from different initiators in the same host to the same I/O group
  • I/O from different initiators in different hosts to the same VDisks
  • I/O from fibre-channel and iSCSI initiators in different hosts to the same VDisks
I/O from fibre-channel and iSCSI initiators in the same hosts to the same VDisks is not supported.

A clustered Ethernet port consists of one Ethernet port from each node in the cluster that are connected to the same Ethernet switch. Because SAN Volume Controller nodes have two Ethernet ports, two clustered Ethernet ports are possible. Ethernet configuration commands can be used for clustered Ethernet ports or node Ethernet ports. SAN Volume Controller clusters can be configured with redundant Ethernet networks.

Two types of authentication through the Challenge Handshake Authentication Protocol (CHAP) are supported:
  1. One-way authentication: iSCSI target (SAN Volume Controller nodes) authenticating iSCSI initiators
  2. Two-way (mutual) authentication: iSCSI target (SAN Volume Controller nodes) 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, SAN Volume Controller requires that both passwords be the same.

iSCSI protocol limitations

When using an iSCSI connection, you must consider the iSCSI protocol limitations:
  • 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.
  • A maximum of 256 iSCSI sessions is supported.
  • Only ErrorRecoveryLevel 0 (session restart) is supported.
  • The behavior of a host that supports both fibre-channel and iSCSI connections and accesses a single VDisk can be unpredictable and depends on the multipathing software.
  • There can be only one session coming from one iSCSI initiator.
The following iSCSI 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
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