Re: [Xen-devel] [PATCH] block: vpc support for ~2 TB disks

["Charles Arnold" <carnold@xxxxxxxx>]

>>> On 11/14/2012 at 09:35 AM, in message <50A3C853.4010809@xxxxxxxxxx>, Paolo
Bonzini <pbonzini@xxxxxxxxxx> wrote: 
> Il 14/11/2012 17:25, Thanos Makatos ha scritto:
>> We don't use qemu's VHD driver in XenServer. Instead, we use blktap2
>> to create a block device in dom0 serving the VHD file in question,
>> and have qemu open that block device instead of the VHD file itself.
> 
> Yes, the question is how you handle disks bigger than 127GB, so that
> QEMU can do the same.
> 

In analyzing a 160 GB VHD fixed disk image created on Windows 2008 R2, it 
appears that
MS is also ignoring the CHS values in the footer geometry field in whatever
driver they use for accessing the image.  The CHS values are set at 65535,16,255
which obviously doesn't represent an image size of 160 GB.

This patch only extends the existing qemu driver to allow a larger image by 
allowing
more heads.  On real hardware, only 4 bits would be allowed for heads but we 
don't
have that restriction in qemu. 

- Charles



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