iSCSI host bus adapters combine the functions of NICs with the function of storage HBA.131 These adapters take the data in block form, handle the seg-mentation and processing on the adapter card with TCP/IP Offload Engines (TOEs), and then send the IP packets across an IP network. The implemen-tation of TOE processors enables users to create an IP based storage area network (SAN) without lowering the performance of the server. Without the TOE processors, software-enabled adapters accept the block data but still re-quire CPU cycles for TCP/IP processing. The advantage of software-enabled adapters is that they work with existing Ethernet NICs. The disadvantage is that they require heavy CPU utilization for TCP/IP processing.132
Other components can be added to an iSCSI SAN to facilitate inclusion of other storage protocols. Bridging products are available to interconnect the iSCSI protocol to Fibre Channel and SCSI devices. This allows users to deploy an iSCSI SAN without requiring forklift upgrades to the entire storage infra-structure.
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