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RE: [Xen-API] How Pygrub work on VHD

To: Anthony Xu <anthony@xxxxxxxxx>, Anil Madhavapeddy <anil@xxxxxxxxxx>
Subject: RE: [Xen-API] How Pygrub work on VHD
From: Ian Pratt <Ian.Pratt@xxxxxxxxxxxxx>
Date: Mon, 25 Jan 2010 23:48:19 +0000
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Thread-topic: [Xen-API] How Pygrub work on VHD
> Now I know how pygrub works,
> before run pygrub, VM system disk is plugged into dom0 as /dev/xvd*
> pygrub grab kernel&initrd from it
> then this disk is unplugged from dom0.
> A curious question,
> When I run HVM VM, VM system disk is still plugged into dom0
> temporarily, I don't think it is necessary. because it is VM bootloader
> to load kernel&initrd in HVM. Maybe I'm missing something here.

The qemu disk emulation accesses the disks via /dev/xvd* until the PV drivers 
start up in-guest. 
> at last, I'd like to get confirmation from you guys, that dd vhd file to
> lvm volume(with same virtual disk size) works,  though it works in my
> experiment:-)

It'll work, though it would obviously be better if you create optimized VHD 
files. Padding the bitmaps to 4KB is probably the most important optimization. 
You can use vhd-util to create VHDs.


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