Re: [Qemu-devel] "A disk read error occurred"

[Jamie Lokier]

Mark Cave-Ayland wrote:
> >Also, sometimes when booting the BIOS can print a disk read error
> >message, and an appropriate -hdachs will fix it.  I found that out
> >when rebooting Windows 2000 after installing it from CD (both in
> >QEMU), on a virtual disk 1GB in size.
> >
> >-- Jamie
> 
> The message "A disk read error occurred" comes from the NT bootloader 
> when it is unable to boot, typically caused by an incorrect drive geometry.
> 
> It sounds as if you are experiencing a similar problem to the one I 
> blogged about here: 
> http://www.ilande.co.uk/index.php?/archives/6-Migrating-an-NT4-VM-from-VMWare-to-NT4-Part-1.html.
>  
> In other words, in order to run an existing NT4 image under QEMU I had to 
> halve the number of heads in the NTFS BPB in order for things to work 
> properly. I suspect that this is a bug in either QEMU/BIOS, but I have no 
> idea where to even start looking.


Yes, very similar, except I saw the problem _without_ migrating
anything.  Windows 2000 was installed _inside_ QEMU (with no special
-hdachs setting) from its CD installer.  It couldn't boot its own
install after restarting QEMU.

I looked at the partition with fdisk, then copied the c,h,s values to
-hdachs...

...and QEMU said the values were out of range and refused to start!

So I guessed some values which were not what fdisk reported, and it
worked and booted fine.

-- Jamie