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2.9.3 iSCSI
Internet SCSI (iSCSI) is an open, standards-based approach by which SCSI information is
encapsulated using the TCP/IP protocol to allow its transport over IP networks. It allows
transfer of data between storage and servers in block I/O formats (defined by iSCSI protocol)
and thus enables the creation of IP SANs. With iSCSI, an existing network can transfer SCSI
commands and data with full location independence and define the rules and processes to
accomplish the communication. The iSCSI protocol is defined in iSCSI IETF draft-20.
For more information about this standard, see:
http://tools.ietf.org/html/rfc3720
Although iSCSI can be, by design, supported over any physical media that supports TCP/IP
as a transport, today's implementations are only on Gigabit Ethernet. At the physical and link
level layers, systems that support iSCSI can be directly connected to standard Gigabit
Ethernet switches and IP routers. iSCSI also enables the access to block-level storage that
resides on Fibre Channel SANs over an IP network using iSCSI-to-Fibre Channel gateways
such as storage routers and switches.
The IBM iSCSI adapters in the 595 server offer the advantage of increased bandwidth
through the hardware support of the iSCSI protocol. The 1 Gigabit iSCSI TOE PCI-X adapters
support hardware encapsulation of SCSI commands and data into TCP and transport it over
the Ethernet using IP packets. The adapter operates as an iSCSI TCP/IP Offload Engine.
This offload function eliminates host protocol processing and reduces CPU interrupts. The
adapter uses a small form factor LC type fiber optic connector or copper RJ45 connector.
Table 2-25 lists the iSCSI adapters that are available for the 595 server.
Table 2-25 Available iSCSI adapter
Feature
Adapter description
code
#5713
Gigabit iSCSI TOE PCI-X on copper media adapter
#5714
Gigabit iSCSI TOE PCI-X on optical media adapter
IBM iSCSI software Host Support Kit
The iSCSI protocol can also be used over standard Gigabit Ethernet adapters. To utilize this
approach, download the appropriate iSCSI Host Utilities Kit for your operating system from
the IBM Support for Network attached storage (NAS) & iSCSI Web site at:
http://www.ibm.com/storage/support/nas/
The iSCSI Host Support Kit on AIX 5L and Linux for Power operating systems acts as a
software iSCSI initiator and allows access to iSCSI target storage devices using standard
Gigabit Ethernet network adapters. To ensure the best performance, enable TCP Large Send,
TCP send and receive flow control, and Jumbo Frame for the Gigabit Ethernet Adapter and
the iSCSI target. Also, tune network options and interface parameters for maximum iSCSI I/O
throughput in the operating system based on your performance monitoring data.
2.9.4 SAS adapters
Serial Attached SCSI (SAS) is a new interface that provides enhancements over parallel
SCSI with its point-to-point high frequency connections. SAS physical links are a set of four
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IBM Power 595 Technical Overview and Introduction
Size
Maximum
Support
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