For better performance and security, you should use separate Ethernet networks to ensure redundant communications between hosts and storage systems. In addition, paths should be handled by separate switching if direct connections are not used.

You should use a dedicated storage network; otherwise, put the iSCSI traffic in either separated network LAN segments or a virtual LAN (VLAN). VLAN allows more than one logical layer 2 networks to share the same physical network while maintaining separation of data and reducing the broadcast domain and collisions.

Ethernet connections to the storage management and the iSCSI ports should use separate subnets. Also, each iSCSI port on a storage processor (SP) should be on a different subnet. Place each port from SP-A on a different subnet. Place the corresponding ports from SP-B on the same set of subnets. The following IP address ranges are available for private networking:

• 192.168.0.0 through 192.168.255.255
• 10.0.0.0 through 10.255.255.255
• 172.16.0.0 through 172.31.255.255

For example, a typical configuration for the iSCSI ports on a storage system with two iSCSI ports per SP would be:

• A0: 172.18.48.10 (Subnet mask 255.255.255.0; Gateway 172.18.48.1)
• A1: 172.18.49.10 (Subnet mask 255.255.255.0; Gateway 172.18.49.1)
• B0: 172.18.48.11 (Subnet mask 255.255.255.0; Gateway 172.18.48.1)
• B1: 172.18.49.11 (Subnet mask 255.255.255.0; Gateway 172.18.49.1)

The preceding configuration could survive two errors: loss of routing on one network and loss of a single SP.

The following is how a simple network topology should be achieved:

• The iSCSI host and storage ports should be on dedicated switches or on a dedicated VLAN on shared switches.
• Network conditions and latency affects bandwidth and throughput rates.
• iSCSI performance is commonly affected by network contentions, routing, and so on. Look at your MTU configuration and if possible use jumbo frames.

• Routed iSCSI traffic increases latency. In an ideal configuration, you should put the host and the iSCSI frontend port on the same subnet, and there should not be any gateways defined on the iSCSI ports. If they are not on the same subnet, users should define static routes.
• iSCSI-based storage system performance gets affected largely by latency in the storage network.

For a balanced bandwidth configuration, follow these points:

• A balanced bandwidth iSCSI configuration is when the host iSCSI initiator's bandwidth is greater than or equal to the bandwidth of its connected storage system's ports. One storage system port should be configured as active/active wherever supported.
• Network settings also affect performance. Follow these points to mitigate it:
  • Use jumbo frames
  • Disable pause frames
  • Disable the TCP-delayed Ack