Converged Fabrics With 10 Gigabit Ethernet; Iscsi - HP N1200 - StorageWorks Network Storage Router Brochure

Converged fabrics with 10 Gigabit Ethernet

One obstacle to using Ethernet as a basis for converged fabrics has been its limited bandwidth. As
10GbE technology becomes more widely implemented, HP expects 10GbE network components to
fulfill the needs of applications that require either the 10GbE bandwidth or its low-latency benefits.
With the emergence of 10GbE, a unified Ethernet switching fabric for all data center applications is
expected to serve as the basis for future data center consolidation and architectural evolution. With
Ethernet and Internet Protocol (IP) as the unified switching fabric, administrators will also have
maximum flexibility in selecting network management tools. As Ethernet bandwidth increases, fewer
physical links can carry more data (Figure 1).
Figure 1. All traffic types sharing the same link
Currently, two of the most promising transport standards for converged fabrics are Internet Small
Computer System Interface (iSCSI) and FCoE.

iSCSI

iSCSI follows the SCSI architectural model, which is based on message exchange between an initiator
and a storage resource, or target. iSCSI initiators access targets using the iSCSI protocol. While the
target is usually a drive enclosure or another computer, it can also be any other storage device that
supports the iSCSI protocol, such as a tape drive. The iSCSI stack at both ends of the path
encapsulates SCSI block commands into Ethernet packets for transmission over IP networks.
Figure 2 illustrates a message exchange between an initiator and a target. The process begins when
an application sends a request to the operating system (OS) to read or write data. The OS generates
the appropriate SCSI commands and data request in the form of a message. Before the message can
be sent over an IP network, it is processed through iSCSI to encapsulate the request into the
Transmission Control Protocol over Internet Protocol (TCP/IP) protocol stack (attaching routing, error
checking, and control information) for transmission over the network. This can be accomplished using
driver-level or OS-level software, or it can be offloaded to the host bus adapter (HBA). The HBA
transmits the packets over the IP network. When the packets reach the target device, they go through
a reverse process to reassemble the data, which is then moved to the SCSI controller. The SCSI
controller fulfills the request by writing data to or reading data from the target device. For a read
transaction, the target returns data to the initiator using the iSCSI protocol.
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