[vbox-dev] fixed - VHD not readable by Hyper-V

[Huihong Luo]

No problem. Can you shed some lights on why writing to vhd is so much slower than to vmdk? Considering that these two are so similar in layout. Only diff is the bitmap on VHD

Sent from my iPhone

On Oct 15, 2009, at 4:24 AM, Klaus Espenlaub <Klaus.Espenlaub at Sun.COM> wrote:

Huihong Luo wrote:
found another bug, I've attached the patch
two bugs:
(1) parent locators set to zero for base images
(2) block allocation table to be block-size aligned (2M)
after these two fixes, vbox vhds works well on Hyper-V, I tested quite some large vhd files from p2v, all works fine now.
These two fixes should be very safe to check in, (not sure if it may break snapshots, though)

Thanks a lot for those fixes (and the previous ones as well), I'll try to find time myself to apply them in the near future - or find someone else who will handle it.

What I wanted to ask earlier already - did you read http://www.virtualbox.org/wiki/Contributor_information ? Which of the two contribution options (SCA or MIT licensed patches) do you pick?

Again, we're very grateful for the excellent contributions.

Klaus

- hl
--- On *Tue, 10/13/09, Huihong Luo /<huisinro at yahoo.com>/* wrote:
   From: Huihong Luo <huisinro at yahoo.com>
   Subject: Re: [vbox-dev] Fwd: VHD not readable by Hyper-V
   To: "vbox-dev at virtualbox.org" <vbox-dev at virtualbox.org>
   Date: Tuesday, October 13, 2009, 1:40 PM
   I found the vhd bug on vbox implementation. vbox mistakenly sets
   parent locators ("wi2r", etc.) for base vhd image. If setting these
   fields to zeros for base image, Hyper-V is happy. Should be very
   easy to fix, if you need the code diff, let me know
   VBox The MS spec states:
   Parent Locator Entries
   These entries store an absolute byte offset in the file where the
   parent locator for a differencing hard disk is stored. This field is
   used only for differencing disks and should be set to zero for
   dynamic disks.
   --- On *Tue, 10/13/09, Huihong Luo /<huisinro at yahoo.com>/* wrote:
       From: Huihong Luo <huisinro at yahoo.com>
       Subject: [vbox-dev] Fwd: VHD not readable by Hyper-V
       To: "vbox-dev at virtualbox.org" <vbox-dev at virtualbox.org>
       Date: Tuesday, October 13, 2009, 6:49 AM
       Sent from my iPhone
       Begin forwarded message:
       *From:* Huihong Luo <huisinro at yahoo.com>
       *Date:* October 13, 2009 6:35:42 AM PDT
       *To:* Shu Wu <superwushu at gmail.com>
       *Subject:* *Re: [vbox-dev] VHD not readable by Hyper-V*

       No problem with vpc, vbox also understands vhds from hyper-v

       It is just that hyper-v doesn't understand vbox's vhd 
       Sent from my iPhone

       On Oct 13, 2009, at 2:27 AM, Shu Wu <superwushu at gmail.com> wrote:

       Can your VHD disk be read by Virtual PC or Virtual Server? It
       seems that Hyper-V and Virtual-PC share the same vhd format.
       One year ago I wrote my own program to generate a vhd file
       and make it to be accepted by Virtual PC, just following the
       official vhd specification. But I haven't tested it on Hyper-V.

       Cheers,

       Wu Shu

       2009/10/13 Klaus Espenlaub <Klaus.Espenlaub at sun.com>

           Huihong Luo wrote:

               None of vbox created vhd disk files are readable by
               2008 Hyper-V.
                This is the error: "The file or directory is
               corrupted and unreadable"
                I am debugging through the code, trying to change
               Footer info, such as version, creator OS, checksun,
               etc., to see it can correct the error.
                If you know what might be wrong, pls post


           We only know what Microsoft documents in their VHD format
           spec, which we believe to have correctly implemented.
           However as usual those specs are incomplete and not
           really precise, so there's plenty of room for different
           interpretations.

           Klaus


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