Re: [Xen-devel] why are qemu-img and vhd-util created files incompatible?

[Darren Shepherd <darren.s.shepherd@xxxxxxxxx>]

Thanks, I'll try out that patch.  I'm using the CentOS 6 bundle of Xen
which pulls in a lot of the newer blktap code.  Do you know if that is
the only thing that prevents snapshots from working?  I have seen
people work around the time issue with just using the faketime
preload, but I think there is something beyond the timestamp that is
incompatible.

Thanks,
Darren

On Tue, Feb 19, 2013 at 4:40 PM, Andrei Lifchits
<andrei.lifchits@xxxxxxxxxx> wrote:
> On Sun, Feb 17, 2013 at 2:30 PM, Darren Shepherd
> <darren.s.shepherd@xxxxxxxxx> wrote:
>> I was wondering if someone can shed some light on why vhd files
>> created with qemu-img don't really work right with vhd-util and
>> consequentially blktap in general.  To validate the incompatiblity its
>> simple enough to do
>>
>> qemu-img create -f vpc test.vhd 40g
>> vhd-util snapshot -n child.vhd -p test.vhd
>>
>> Which will show the below and then the headers don't display the BATMAP 
>> summary:
>>
>> primary footer invalid: creation time in future
>
> This is due to a bug in the blktap2 code which uses local time instead
> of UTC (which is mandated by the VHD specs). I fixed it recently in
> the Citrix fork of blktap
> (https://github.com/xen-org/blktap/commit/a79ac2c05f97c2384bbf981419f329f184dc646a),
> but unfortunately these two forks aren't really kept in sync.
>
>> test.vhd appears invalid; dumping metadata
>> Failed to open test.vhd: -22
>>
>> Additionally "vhd-util snapshot -n child.vhd -p test.vhd" will give
>> you the same 22 error.
>>
>> I was going to start researching this with the eventual goal of
>> changing qemu-img, but I thought I'd ask the experts first.
>>
>> Thanks,
>> Darren
>>
>> _______________________________________________
>> Xen-devel mailing list
>> Xen-devel@xxxxxxxxxxxxx
>> http://lists.xen.org/xen-devel

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