Opened 13 years ago

Closed 9 years ago

#9643 closed enhancement (fixed)

VBoxManage showhdinfo should show data alignment

Reported by: Sven Owned by:
Component: other Version: VirtualBox 4.1.2
Keywords: Cc:
Guest type: other Host type: other

Description (last modified by Frank Mehnert)


it would be very useful, if VBoxManage would show the alignment of the datablocks inside the VDI file. There are tools out there (CloneVDI, tool announced in the forums) which modify the alignment of the data such that sector 63 of the virtual harddisk is aligned to 4K. While this is good for Windows XP/DOS and the default partition layout, it is bad for Windows where partitions start at a 1MB boundary.

Also, there seem to be "old" VDI files, where data blocks are not aligned on a 4K boundary which AFAIK results in poor AIO/DIO performance. For example I have a flat VDI file with Windows 7 on it, where the MBR is at offset 0x20200 within the file (which is a 512 byte boundary, and not a 4KB boundary). I had to verify this using a hex editor.

I would suggest that VBoxManage shows

  • the offset of the first data block in the VDI file
  • the first sector of the virtual harddisk which is aligned to a 4K boundary (some value in the range of 0 to 7)

Change History (2)

comment:1 by Frank Mehnert, 13 years ago

VBoxManage internalcommands dumphdinfo IMAGE prints out the data offset.

comment:2 by Frank Mehnert, 9 years ago

Description: modified (diff)
Resolution: fixed
Status: newclosed

The data offset is also shown by vbox-img (shipped with VBox 5.0.x).

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