ISS Technology Update Volume 8, Number 5

drive. The iSCSI stack at both ends of the path is used to encapsulate SCSI block commands into Ethernet Packets for

transmission over IP networks as illustrated in Figure 2-1.

Figure 2-1. iSCSI is SCSI over TCP/IP

SCSI MP**

SCSI

Disk Driver

File System

TCP/IP

iSCSI MP**

SCSI

Disk Driver

File System

Ethernet

TCP/IP

iSCSI SCSI

Direct attached block

storage using

SCSI/SAS

Remote block storage using iSCSI

Ethernet

iSCSI target

iSCSI initiator

* Serial Attached SCSI

** Multipathing

Ethernet

Initiators include both software- and hardware-based initiators incorporated on host bus adapters (HBAs) and network interface

cards (NICs). Software initiators require CPU resources to manage the iSCSI protocol stack. A more efficient approach is to

offload the protocol management to a hardware-based iSCSI HBA or NIC. The operating system sees an iSCSI HBA or NIC as

a SCSI device.

Accelerated iSCSI

Traditional software-based iSCSI initiators generate more processing overhead for the server CPU. By contrast, HP accelerated

iSCSI offloads the protocol processing to an HP Multifunction Server Adapter so that CPU utilization is reduced and iSCSI

performance is accelerated. HP Accelerated iSCSI supports all targets that are certified and supported by Microsoft iSCSI

Software Initiator.

ProLiant servers utilizing Accelerated iSCSI Multifunction server adapters show significant improvements in server efficiency over

software-based iSCSI initiators. For more on the performance gains experienced with the Broadcom solution for HP hardware-

assisted iSCSI Multifunction server adapters, read test results from the Tolly Group at

http://www.tolly.com/TS/2008/HewlettPackard/iSCSISolutions/Tolly208305HPiSCSI.pdf.

HP Accelerated iSCSI technical advantages

There are several advantages derived from implementing Accelerated iSCSI:

Standard configurations, including ideal input/output (I/O), read/write, random/sequential and queue sizes

Improved I/O operations per second (IOPS) compared to iSCSI host bus adapters from other vendors

Processing work offloaded to the NIC to free CPU cores for data-intensive workloads

Increased server and IP storage application performance

Increased iSCSI performance