7.8 Chapter Summary

Gigabit Ethernet Switches

• Gigabit Ethernet switches provide layer 2 link switching and layer 3 IP routing.

• Gigabit Ethernet switch products range from 8 to more than 200 ports.

• Port density is achieved through small form factor transceivers and RJ-45 connectors.

• A Gigabit Ethernet switch can support multiple transmission speeds.

• Cut-through switching routes packets based on destination address.

• Store-and-forward switching buffers the entire packet before routing.

• 10Gbps interswitch links enable scalable, high-performance core networks.

• Gigabit Ethernet switches support both IEEE and IETF standards.

• Gigabit Ethernet directors can be used to build highly available data center SANs.

IP Routers

• An IP router supports both Ethernet and wide area connectivity.

• WAN links can include Packet over SONET, ATM, ISDN, frame relay, and point-to-point.

• WAN link speeds range from T1 (1.544Mbps) to OC-192c (10Gbps).

• IP storage traffic appears as standard IP packets to an IP router.

• IP routers can incorporate QoS and IP security functionality.

iSCSI Adapter Cards

• iSCSI can be implemented in software or offloaded in silicon to a Gigabit Ethernet NIC.

• iSCSI adapters require TCP off-load engines (TOEs) to minimize host CPU utilization.

• Pricing for iSCSI adapters is midway between standard Gigabit Ethernet NICs and Fibre Channel HBAs.

• iSCSI adapters are changing the composition of SANs from predominantly Fibre Channel to predominantly IP.

iSCSI Storage Devices

• The functionality provided by storage arrays and tapes is not changed by substitution of iSCSI for Fibre Channel at the interconnection.

• iSCSI interfaces on storage targets provide flexibility in deployment of storage assets.

• JBODs will probably remain SCSI or Fibre Channel-attached.

• iSCSI-enabled storage is suitable for both data center and low-end storage applications.

IP Storage Gateways

• IP storage gateways can provide Fibre Channel-to-iSCSI or Fibre Channel-to-iFCP protocol conversion.

• IP storage gateway architecture can employ fixed ports for Fibre Channel or Gigabit Ethernet or multiservice ports that support both.

• IP storage gateways provide E_Port connectivity to existing Fibre Channel fabrics.

• iSCSI may not be suited to data replication between Fibre Channel storage arrays.

• iFCP gateways provide protection against Fibre Channel fabric reconvergence issues.

iSCSI-to-SCSI Bridges

• iSCSI-to-SCSI bridges enable legacy SCSI tape and disk to be integrated into an IP SAN.

• Bridge products can include extended copy agents to facilitate server-free tape backup.

• iSCSI-to-SCSI bridges extend the useful life of SCSI assets by leveraging them for new SAN-enabled storage applications.

iSNS Servers

• iSNS servers allow centralized discovery, zoning, and security for IP SANs.

• iSNS server products can be third-party devices in the IP network or can be integrated into more comprehensive storage management frameworks.