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Chapter VII. iSCSI PDU Offload Target

1.2.2. Adapter Requirements

The Chelsio iSCSI PDU Offload Target software can be used with or without hardware protocol

offload technology. When used with protocol offload, a Chelsio TOE adapter must be used.

There are four modes of operation using the iSCSI PDU Offload Target software on Ethernet-

based adapters:

Regular NIC (non-Chelsio NIC Adapter)  The software can be used in non-offloaded

(regular NIC) mode. Please note however that this is the least optimal mode of operating the

software in terms of performance.

TOE HW Accelers)  In TOE mode the software

            

additional benefit of iSCSI HW acceleration).

iSCSI HW Acceleration (Uses T4xx Series adapters)  In addition to offloading the

            

capability of hardware assisted iSCSI data and header digest calculations as well as using

the direct data placement (DDP) feature.

Mix of iSCSI HW Acceleration and TOE HW Acceleration (Uses T4xx Series adapters) 

Using a special software mode the stack can be configured to change between iSCSI

acceleration or just TOE acceleration, depending if digests are used or not.

1.2.3. Storage Requirements

When using the Chelsio iSCSI target, a minimum of one hardware storage device is required.

This device can be any of the device types that are supported (block, virtual block, RAM disk).

Multiple storage devices are allowed by configuring the devices to one target or the devices to

multiple targets. The software allows multiple targets to share the same device but use caution

when doing this.



of configurations. For quick testing, using a RAM Disk as the block storage device works nicely.

For deployment in a production environment a more sophisticated system would be needed.

That typically consists of a system with one or more storage controllers with multiple disk drives

attached running software or hardware based RAID.

1.3. Software Requirements

chiscsi_base.ko is iSCSI non-offload target mode driver and chiscsi_t4.ko is iSCSI PDU

offload target mode driver.

cxgb4, toecore, t4_tom and chiscsi_base modules are required by chiscsi_t4.ko module to

work in offloaded mode. Whereas in iscsi non-offloaded target (NIC) mode, only cxgb4 is

needed by chiscsi_base.ko module.

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Chelsio Communications Chelsio T4 Guía de usuario Pagina 93