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In the future we'll move from local storage for our VMs to an iSCSI-based solution. Our server vendor supports Broadcom NetXtreme II 5709 cards with dual gigabit ports and TOE + iSCSI acceleration. They would be used in A/P multipath to a Dell MD3220i SAN.

I can run the iSCSI initiator on the dom0 or in the domU, and I'm investigating if there is any pro or con between the two.

I'm assuming an iSCSI initiator in dom0 will make good use of the hardware offload of the BCM5709.

What about running the initiator in the domUs? Is it at all possible? Will it make use somehow of the iSCSI engine in the ethernet cards (I suspect some SR-IOV or similar support would be needed for this)? I could see a little bonus in not having to explicitly configure all LUNs on all dom0 and let each VM manage its own, but I don't know if there would be any drawback...

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Initiator in domU can work in domU hvm with their speed limits. For better perfomance, you need to use some paravirtualized network drivers in domU operation system, but not all features can be realized in that drivers. Also, not all distro of guest oses support paravirtual driver.

Ofcourse, you have better iscsi perfomance in dom0. It makes independ guest oses from iscsi, so u can even boot from this devices. Iscsi connection cant be managed from guest os in this case, guest os just gets block device (hdd).

You can setup xen containers to using separeted luns (iscsi block devices) for each one.

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