[vbox-dev] VHD child disk imcompatible with Windows 7 vhdmp driver or Hyper-V

[Huihong Luo]

Actually, VBox does emit parent locator info to the diff disk. However, it seems that Microsoft made a mistak in VHD spec regarding to 
Parent Locator Entries
 
Platform Data Space. This field stores the number of 512-byte sectors needed to store the parent hard disk locator.
Platform Data Length. This field stores the actual length of the parent hard disk locator in bytes.

 
the spec says Platform Data Space should be number of sectors, but Windows 7 or hyper-V actually checks that data as number of bytes, vbox puts 1 for 1 sector, but MS puts 0x200.
 
When I change u32DataSpace to be number of bytes, then VBox diff files are recognized.
 
vbox team can decide whether to change this. I will check what vmware is doing on this.

 


--- On Sat, 10/1/11, Huihong Luo <huisinro at yahoo.com> wrote:


From: Huihong Luo <huisinro at yahoo.com>
Subject: Re: [vbox-dev] VHD child disk imcompatible with Windows 7 vhdmp driver or Hyper-V
To: vbox-dev at virtualbox.org
Date: Saturday, October 1, 2011, 10:29 AM







error was due to the lack of parent locators. VBox doesn't emit any parent locator info to the child disk. Windows 7 vhdmp driver or hyper-V relies on parent locator info to find the base disk.
 
I will see if I can add the code.

--- On Sat, 10/1/11, Huihong Luo <huisinro at yahoo.com> wrote:


From: Huihong Luo <huisinro at yahoo.com>
Subject: [vbox-dev] VHD child disk imcompatible with Windows 7 vhdmp driver or Hyper-V
To: vbox-dev at virtualbox.org
Date: Saturday, October 1, 2011, 9:39 AM







receives "The file or directory is corrupted and unreadable" if mouting a child disk created by vbox using vhdmp driver on windows 7. (Base disk works fine)
 
I will debug this.
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