Hello,
I've documented a reproducible case where Windows sees large disks (over
2TB) as the total disk size minus 2TB. When I use 'VBoxManage
storageattach ...' to add the disk to a running Windows VM, this causes
Windows to decide that the backup GPT header is missing, so it writes a
new backup header at the location that it thinks is the end of the disk
(2^32 sectors from the end of the disk); this corrupts whatever file is
at that location. This occurs in any version of Windows that's running
the NT5 kernel and has GPT support, which includes Windows 2003 SP1 and
later along with Windows XP x64 Edition.
I have verified that the corruption occurs only when the disk is
attached to a SATA controller on the VM, and the same corruption occurs
using KVM as the virtualization platform; it does not occur on a
physical system (based on a Gigabyte GA-D525TUD motherboard, which has
the NM10 Express chipset - I do not have access to any ICH8 or ICH9
physical systems). It does not occur if you boot the same VM using a
Linux LiveCD ISO image, which leads me to believe that it's a bug in
either Microsoft's Windows SATA code or Intel's SATA controller driver
that only manifests itself when virtualized.
Aside from the incorrect sizing and GPT header/data corruption,
something is preventing the Windows bootloader from loading if the large
volume is attached to the VM before booting. If you attempt to boot the
machine with a large (>2TB) volume attached to a SATA or SCSI
controller, it freezes at a black screen with no cursor. If I create an
unpartitioned, empty raw disk and attach it to a SCSI controller on the
VM, Windows is able to boot and then I can use Disk Management to
partition and format its full capacity. However, once I shut down (or
reboot) the machine, it will no longer boot, freezing at a black screen
with no cursor just the same as when attaching the volume to the SATA
controller.
I had a brief discussion with Klaus in #vbox on Freenode, during which I
reproduced the bug as follows:
largevolume-vbox13.vmdk is a text header file with no data, pointing to
largevolume-vbox13.raw; see its contents here:
http://paste.ubuntu.com/1071285/
largevolume-vbox13.raw is a 2726162350592 byte (approximately 2.5TiB)
GPT partitioned with a single NTFS partition; see its partition table
throughout the tests here: http://paste.ubuntu.com/1071279/
First boot: In the VirtualBox GUI, I attached largevolume-vbox13.vmdk to
port 1 of the virtual machine's SATA controller. The machine freezes at
a black screen with no cursor, shortly after the VirtualBox BIOS splash
screen. See the VBox.log file for this boot here:
http://paste.ubuntu.com/1071275/
Second boot: Windows was booted without largevolume-vbox13.vmdk
attached, then it was attached to the VM once Windows had reached the
GUI and I logged in. As soon as the disk becomes visible in Disk
Management, the partition table gets corrupted, as can be seen in the
partition tables pastebin (http://paste.ubuntu.com/1071279/). See the
VBox.log for this boot here: http://paste.ubuntu.com/1071276/
Third boot: I created an unpartitioned raw disk image and VMDK as
documented in the last entry in the partition table pastebin
(http://paste.ubuntu.com/1071279/). Windows recognized the disk as a
490.9GiB drive and partitioned it accordingly (as an MBR disk) when I
followed the new disk initialization wizard. See the VBox.log for this
boot here: http://paste.ubuntu.com/1071277/
In this screenshot, I had booted the Windows VM, then attached the drive
to a port on its SATA controller; notice that Disk Management is showing
the correct volume size (2538.94GB), wmic is showing the incorrect size
for the volume (527133519360 bytes), and gdisk is showing an incorrect
total volume size (490.9GiB) and the correct partition size (2.5TiB).
http://imagebin.org/219211
The same situation in KVM: http://imagebin.org/217124
The data corruption issue is causing serious problems for me, and using
the SCSI controller could be a workaround if it supported hotplugging.
Some additional reading:
Mentions a situation in which Windows can hit a black screen with no
cursor while booting:
http://blogs.msdn.com/b/ntdebugging/archive/2007/06/19/how-windows-starts-up-part-1-of-4.aspx
Talks about storage drivers incorrectly accessing disks larger than 2TB:
http://support.microsoft.com/kb/2581408
A discussion in which a 2TB limit on ICH8 is discussed, although it's
only mentioned specifically in the context of the controller's RAID mode:
http://www.tomshardware.com/forum/page-216247_30_50.html
Thanks in advance...
Matt
--
*Matthew Coleman*
Developer :: Datto Inc. :: www.dattobackup.com :: (203) 710-4470
_______________________________________________
vbox-dev mailing list
[email protected]
https://www.virtualbox.org/mailman/listinfo/vbox-dev
