Disk Utility repartition destroys hybrid MBR, Windows no longer boots
Disk Utility repartition destroys hybrid MBR, Windows no longer boots
- Subject: Disk Utility repartition destroys hybrid MBR, Windows no longer boots
- From: Chris Murphy <email@hidden>
- Date: Sun, 02 Jun 2013 17:54:19 -0400
Problem ID: 11980880
I'd like to call attention to this issue because whoever in engineering reported back on this bug wasn't paying attention. Many users are experiencing data loss as a result of this bug.
Engineering reports:
> This is a limitation of Windows.
It's not. It's a limitation of BIOS/MBR. If Windows were installed on UEFI/GPT the problem wouldn't occur.
>
>
> Adding a extra HFS partition will break windows.
Because when adding that 5th partition, Disk Utility nukes the hybrid MBR, replaces it with a protective MBR, and therefore there isn't a Windows entry in the partition table. Disk Utility behavior in this scenario directly leads to data loss.
> We can not prevent this.
Yes you can. Don't allow users to create a 5th partition when there is a hybrid MBR.
I cite this Apple technote:
http://developer.apple.com/library/mac/#technotes/tn2166/_index.html
Please see the 2nd paragraph under the Protective MBR heading. Disk Utility is a GPT aware program, LBA 0 contains an "other form" of MBR, a hybrid MBR, Disk Utility should "refuse to manipulate the disk" per this technote. Yet Disk Utility isn't following Apple's own technote guildeline in this scenario. Further it says "manipulating the GPT may cause dangerous inconsistencies between it and the legacy MBR". How about that, the user experiences data loss as a result of adding a 5th partition, just as the Technote predicts.
Thank you.
Chris Murphy
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