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Hyper-V Using Guest iSCSI Initiator

Intel, pushing 10 Gigabit Ethernet (10 Gig-E) for a number of reasons, just published a recent report outlining over one million I/O operations per second (IOPS). One of the comments from the report's associated Webcast mentions the practice of assigning the iSCSI Initiator in the guest virtual machine. This is a fundamental, reverse perspective for all virtualization platforms that should be really considered.

Before I go into what I think of this material, consider the fact that achieving 1 million IOPS is, for all intents and purposes, applicable to no one. Besides, the disk used was RAM and I don't have a RAM SAN for the virtualization circles I cross. But it would be darn cool.

Now, back to the takeaway of the Webcast related to Hyper-V and the iSCSI Initiator for Windows Server 2008 R2 and Hyper-V. The material is out to prove that any workload can be done on the software initiator using the Intel 82559 controller.

One comment on the material is that administrators may choose to use the virtual machine's initiator. This would have the guest virtual machine communicate to the iSCSI storage directly. This would not apply to the Windows boot volume with the software initiator, but this would be a nice roadmap item. Putting one and two together, you can see that this can put a relief on the shared storage requirements of the guest virtual machine.

In VMware circles, the hands-down recommendation would be to use the VMFS file system; I've never heard of a recommendation to use in-guest software initiators. Even so, there are use cases for a raw device mapping (RDM). For a Hyper-V installation, this may be an architecture that can work well into tiered storage to put the operating system drives on a designated clustered shared volume, and the guest storage would go directly to the iSCSI storage resource.

While 10 Gig-E is not necessarily available everywhere yet, future designs may benefit from a potentially simpler host configuration and lessened reliance on the clustered shared volumes storage resources for potentially large virtual machines.

What do you think of in-guest iSCSI initiators from a design perspective? Comment below.

Posted by Rick Vanover on 02/25/2010 at 12:47 PM


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