Extra 8 bytes for each partition in "DiskVolumeInfo" x64 ?

Hi,

MS describes the structure of  "DiskVolumeInfo" that for 2008 cluster X64, each partition info is record as 40 bytes:

8 bytes: starting offset

8 bytes: partition length

4 bytes: partition number

4 bytes: drive letter

16 bytes: GUID

While I have a test on windows enterprise 2008 R2 X64, I find that there are extra 8 bytes right after GUID.

The cluster command:

cluster . res "cluster disk 3" /priv

---------------------------

Listing private properties for 'cluster disk 3':

B cluster disk 3 DiskVolueInfo 01 00 00 00 ... (56 bytes)

---------------------------

This cluster disk has only one volume. We can find that the "DiskVolumeInfo" has 56 bytes! Which is 8 + 48, rather than 48 bytes.Those extra 8 bytes are all filled with 0x00.

And I also test other disks with multiple partitions, all of them are 48 bytes for each partition.

This result is different from some case shown in the internet that may with the "correct" value 40 bytes.

Does anyone knows why different here?

Thanks.