Dynamic VHD attached to disk management increases in size

Question

When attaching a dynamic VHD to the disk management, the size of the VHD gets increased by some 32 MB, why does this happen ? What information does the disk management writes to the VHD. When attaching the VHD in read only mode, the Size remains the same.
VHD Spec : The VHD is created using a utility.
                  The VHD has a Block Size of 524288 Bytes. 
Thanks,
Sajith

Answer 1

The block allocation table adds to the size of a dynamic disk, an expanded dynamic disk will show larger than a fixed disk of the same usable space because of this.  In addition there is a hard drive header and footer almost like a header and footer
on a word document, it is always present on a dynamic disk which adds space compared to a fixed disk.
See this Microsoft document for additional information:
https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=4&ved=0CEYQFjAD&url=http%3A%2F%2Fdownload.microsoft.com%2Fdownload%2Ff%2Ff%2Fe%2Fffef50a5-07dd-4cf8-aaa3-442c0673a029%2FVirtual%2520Hard%2520Disk%2520Format%2520Spec_10_18_06.doc&ei=fbLrUsuHK4WCyQGsi4DICQ&usg=AFQjCNF_2gpgEA65OhmSPr8R_InwjL2TqQ&sig2=gau_qlwZonH3LJ9wYiiu6g&bvm=bv.60444564,d.aWc&cad=rja
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