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BP1028 EqualLogic iSCSI for Fibre Channel Professionals 7
5 Host adapters/interface card comparison
5.1 FC host bus adapters
In the FC architecture, each host has (preferably) at least two FC HBAs, which provide the hardware
and logic to connect the host server to the FC SAN. A number of vendors produce FC HBAs with
varying capabilities including speed, number of ports, connector types (optical, copper, etc.), bus
interfaces (PCI-X, PCI-e), and buffer memory sizes. The FC HBA contains a task-specific processor
responsible for SERDES (serial/de-serial operations) and frame processing, moving data between the
host bus and FC connections, and is usually independent of host processors.
5.2 iSCSI network interface cards
iSCSI SANs are connected using either a simple Ethernet NIC (in conjunction with a software iSCSI
initiator) or a dedicated iSCSI HBA. If a standard Ethernet NIC is used with a host-based software iSCSI
initiator, it shares or borrows host-processor cycles to move data and to process TCP packets. More
advanced Ethernet NICs offer offload processing capabilities -- such as TCP Offload Engine (TOE) or
iSCSI Offload Engine (iSOE) -- to offload the packet processing from the host. Ethernet cards also
vary in their implementation and various models offer larger internal buffers or different connectivity
options (copper vs. optical network connections or PCI-e vs. PCI-X host-bus connectivity).
Purpose-built iSCSI HBAs are also available. These are similar to FC HBAs in that they contain a
dedicated processor that handles all iSCSI and usually TCP packet processing. Dedicated iSCSI HBAs
generally cost more than standard Ethernet NICs, but may offer additional features such as iSCSI boot
ROMs that enable boot from SAN capability.
An iSCSI HBA can be selected that is specifically designed for iSCSI traffic, or an Ethernet NIC can be
selected and used with a host-based software iSCSI initiator. The
Validated Component List for
EqualLogic PS Series SANs
provides detail of which interface cards are tested and proven to work with
EQL iSCSI arrays. Dell recommends evaluating these options prior to making an investment in a
particular NIC or iSCSI HBA.
Note: The
Validated Component List
can be downloaded from delltechcenter.com:
http://www.delltechcenter.com/page/EqualLogic+Validated+Components