You can fit 12 HDDs into one 2U Server. I calculate with 18Tb HDDs as these are the best €/Tb here at the moment. You can fit 24TB HDDs in there and could get theoretically 288Tb into one 2U Server.
But they wrote me, that they are searching for people in the US, who can provide at least 1Pb. - But they may consider other regions too.