iSCSI target and iSCSI offload engines

[luke404]

I often come accross network cards with iSCSI offload engines such as the Broadcom BCM5709 (eg. I have them in Dell servers with linux and open-iscsi initiators), but there are other similar cards on the market.

When using such a card in a FreeNAS system acting as iSCSI target, does the offload engines "kick in" and actually offload work from the main CPU, or is that an initiator-only feature?

 

[jgreco]

I believe it to be an initiator-only feature, and would require device driver support from the manufacturer, which I don't think FreeBSD has anyways.

 

[ixdwhite]

Correct; FreeNAS does not support NIC iSCSI offload functions on any card at current. Then again, FreeNAS is a purpose-built NAS solution, and spending CPU time on providing NAS services is perfectly reasonable. Its not been my experience that iSCSI offload is a performance benefit to iSCSI itself; its more that an initiator can spend less CPU time on iSCSI and spend it on other things.

iSCSI offload use on the initiator side is of course supported as long as the offload is iSCSI protocol compliant. FreeNAS has no idea iSCSI initiator offload is in use.