Comment 6 for bug 1387380

The important factor is that the good nodes second <size> tag was nested in:

        <node id="volume" claimed="true" class="volume" handle="">

whereas the bad node did not have this <node> tag.

The XPath expression that MAAS uses to calculate the total storage is:

    sum(//node[@class='volume']/size[@units='bytes'])
    div 1024 div 1024