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I'm planning to update my server from Win Server 2008 Rs to 2012 when it is released. I'm very interested in the new "Storage Spaces". The main question I have is whether I can mount a storage space into a Hyper-V VM directly (like I can with physical disks in the current version)

Unfortunately I have no hardware to test it on at the moment and I can't test that in a VM (Hyper-V can't install inside a Hyper-V VM) and I could not find a definite answer on the internet either.

Has anyone of you tested such a setup?

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when you say "Hyper-V VM directly" do you mean as a passthru disk? – tony roth Jul 13 '12 at 15:10
yes, that's what I meant to say – Apollo Jul 13 '12 at 15:35

Yes, you could mount it into a VM as a pass-through disk. But what would that get you? You'd have a VM that's not portable, not able to migrate, not able to snapshot, not able to back up.

You'd be much better off putting a VHDX file on that space and mounting that in the VM. And, though this might not be your response, most people I've had this conversation with immediately countered, saying that they didn't want the performance overhead of the VHD. I challenge you to measure it. See if you can find any meaningful difference between pass-through disks and VHDX files.

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the thing about vhd vs passthru is that you could have 20 vms running off one lun thus performance will be impacted. So if you want more consistent performance use passthru. – tony roth Jul 13 '12 at 17:53
A storage space is no more separate from the underlying storage than a VHD is. It's just some storage taken from a bunch of underlying LUNs. Tony, are you just arguing that it's easier to lose track of managing your storage with VHDs? I might buy that. But it seems easier to just say that if you want dedicated performance, you need to make sure that you're not sharing with the wrong workloads, which you can do with VHD files almost as easily. – Jake Oshins Jul 13 '12 at 20:39
I think you may be confusing native boot vhd performance vs vhd's on shared media. The more vm's you have on a lun the less performance you'll have. I've never seen a ms doc that disputes this. – tony roth Jul 13 '12 at 21:25
No, I'm not confusing them, and I don't dispute that. But you could say just as usefully, the more Spaces you have spread across a few physical LUNs the less performance you'll have. A VHD file and a Storage Space are really much more alike than they are different. They both take a bunch of storage extents from an underlying media and present a virtual disk interface. They both can be the only virtual disk on that underlying media or they both can share it. – Jake Oshins Jul 13 '12 at 21:31
ok we are arguing about different things here, extract storage spaces from the argument and concentrate on your statement "saying that they didn't want the performance overhead of the VHD. I challenge you to measure it. See if you can find any meaningful difference between pass-through disks and VHDX files." its easily measurable once you go beyond a single vhd per lun. – tony roth Jul 13 '12 at 22:23

I'm quite sure the answer would be that if you used the storage pool as an iscsi target then yes otherwise no.

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with 2012 smb3 you can host vhd's but they won't be passthru. – tony roth Jul 13 '12 at 15:48
darn was thinking of connecting to a remote storage pool not local! – tony roth Jul 13 '12 at 17:50

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