IBM Midrange System DS4000 Series Hardware Manual page 149

Hardware initiators
As of the writing of this book, only the following hardware initiators are supported:
IBM iSCSI Server TX Adapter
IBM iSCSI Server SX Adapter
QLogic iSCSI Single-Port PCIe HBA for IBM System x
QLogic iSCSI Dual-Port PCIe HBA for IBM System x
All of the hardware initiators that are supported use the same base firmware code and the
SANsurfer management application. Before you install and configure these adapters, make
sure that you have installed the latest management application and the latest firmware code.
Software initiators
The native MPIO that is provided with the Microsoft iSCSI Software Initiator (Version 2.03 or
later) is not supported. You must use the DSM that is provided with the Storage Manager
software to make sure that failover and I/O access are correct. If the native MPIO from the
Microsoft iSCSI Software Initiator is used, it might cause unwanted effects.
Partitioning
As described in 4.1.4, "Storage partitioning" on page 116, because the FC and iSCSI
protocols provide radically different latency and throughput capabilities, and this mixture
within a server might cause failover driver conflict, performance degradation, or potential data
loss, you have to plan ahead by using the following recommendations:
Define separated partitions for FC-based hosts from iSCSI-based hosts, avoid mixing
them in same storage partition.
A single host should not be configured for both iSCSI connections and FC connections to
the storage system.
In order to define hosts and partitions in iSCSI, remember that you have to plan for iSCSI
addresses for the host ports, and use the iSCSI qualified name (IQN) of the host you want to
map.
Network settings
Unlike traditional Fibre Channel, which requires special cabling and SAN switches, iSCSI can
be run over an existing network infrastructure. However, in complex network environments,
and in order to protect the integrity of the data in your DS5000 storage subsystem, and its
continuous access, we suggest that, whenever possible, to try to isolate the iSCSI traffic in a
dedicated network. The iSCSI multipathing architecture provides failover to the alternate
controller in the event of an outage situation. Also with MPIO, IBM provides DSM, which also
offers load-balancing algorithms.
For better redundancy, you can increase the availability of your connections using redundant
networks, so a failure in one does not interrupt the remaining redundant connection.
Aside from the basic iSCSI connectivity parameters, such as IP address per target Ethernet
port and associated iSCSI qualified names, you have to plan in advance several optional
configuration parameters, including ennoblement of jumbo frames, configuration of a VLAN,
and setting a specific Ethernet priority:
Jumbo frames are created when the MTU is adjusted above 1500 bytes per frame, and
they are set by port. The frame sizes supported are of 1500 and 9000 bytes. When using
jumbo frames, ensure that all of the devices on your iSCSI network, including switches,
initiators, and targets, are configured to use the same maximum jumbo frame size.
Chapter 4. IBM System Storage DS planning and configuration
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