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Does anyone have any numbers or good resources on the disk IO performance penalty for a non-enlightened guest(Windows XP) vs enlightened guest (Windows 7) running in a hypervisor?

Hyper-V in particular, but VMWare ESX numbers would also be useful.

I haven't done serious experimenting yet, but in the case of XP I noticed very poor disk performance initially. There may also be some obvious tips for configuring for good disk performance. I started at dynamic disk (bad), moved to fixed disk (still bad), then moved to direct disk access (better, but not great).

This is a basic test so far - a single VM. I'm still experimenting and early planning. My goal is consolidation, even if each VM still needs its own disk (build server load which is CPU and IO intensive). Windows 7 is an option but I will also need at least a couple running XP.

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Install Enlightment.

Without it is not the hyper-v subsystem that is bad, it is at the end... the simulated slow ide interface, compared to a fast multi request capable scsi interface.

That said, you need not a separate disc per client, but a lot of discs. I run about 20 virtual servers out of an 8 disc raid on hardware raid with velocirapors. WOrks like a charm. Hyper-V and any virtualization turns prettxy much all IO random...

I now move to a SSD for my personal virtual workstation (I do a lot of compiles). NExt step after isa proper small SAN, with FS, deduplication.

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Do Hyper-V or equiv VMware tools make an older OS like XP gain the same full enlightenment benefits as an OS like Windows 7? I am a bit unclear on the role each plays... I get that an enlightened OS knows when it's inside a VM, but beyond that...are the virtualized drivers coming from that knowledge or from the VM tools (which should be installed already) –  Joshua McKinnon May 20 '11 at 4:00
    
Depnds whether yo ucan install them. If yes (i.e. supported), then yes. The are in the end specialized drivers. –  TomTom May 20 '11 at 4:33

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