IBM System Storage DS3500 Introduction And Implementation Manual page 34

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Hardware initiator
A hardware initiator uses dedicated hardware, typically in combination with software
(firmware) running on that hardware, to implement iSCSI. A hardware initiator mitigates
the overhead of iSCSI and TCP processing and Ethernet interrupts, and therefore may
improve the performance of servers that use iSCSI.
An iSCSI host bus adapter (more commonly, HBA) implements a hardware initiator. A
typical HBA is packaged as a combination of a Gigabit (or 10 Gigabit) Ethernet NIC, some
kind of TCP/IP offload engine (TOE) technology and a SCSI bus adapter, which is how it
appears to the operating system. Inside the operating system, the iSCSI HBAs are
classified as storage adapters.
An iSCSI HBA can include PCI option ROM to allow booting from an iSCSI target.
A TCP Offload Engine, or "TOE Card", offers an alternative to a full iSCSI HBA. A TOE
"offloads" the TCP/IP operations for this particular network interface from the host
processor, freeing up CPU cycles for the main host applications. When a TOE is used
rather than an HBA, the host processor still has to perform the processing of the iSCSI
protocol layer itself, but the CPU overhead for that task is low.
iSCSI HBAs or TOEs are used when the additional performance enhancement justifies the
additional expense of using an HBA for iSCSI, rather than using a software-based iSCSI
client (initiator).
An iSCSI target usually represents hard disk storage that works over the IP or Ethernet
networks. DS3500. Other types of peripheral devices, like tape drives and medium changers,
can act as iSCSI targets as well.
iSCSI naming
The iSCSI initiators and targets on a SAN are known by their respective iSCSI names, which
must be unique. The iSCSI name is used as part of an ISCSI address, as part of all sessions
established between initiators and targets. Next, we describe two types of iSCSI names:
IQN
EUI
NASA
IQN
A commonly used format of iSCSI names is the
an IQN is:
iqn.yyyy-mm.{reversed domain name}
For example, an iSCSI HBA inside a host server named Rhine in the domain rivers.local
would be assigned the following IQN:
iqn.2010-08.local.rivers.rhine
The DS3500 uses IQN names.
EUI
An alternative type of iSCSI name is the Enterprise Unique Identifier (EUI). The format of an
eui
EUI is
eui.acdc15882005bdef
NASA
NAA name formats were added to iSCSI to provide compatibility with naming conventions
used in Fibre Channel and Serial Attached SCSI (SAS) storage technologies.
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IBM System Storage DS3500: Introduction and Implementation Guide
plus 16 hex digits. For example:
Draft Document for Review March 28, 2011 12:24 pm
iSCSI Qualified Name
(IQN). The format of