http://www.channelregister.co.uk/201...m_dcs9900_2tb/

With the 2TB drives, IBM says a rack of DCS9900 storage can hold up to 1.2PB, with a maximum of 2.4PB in two racks containing 1,200 drives.
PB = Petabyte = 1,000 Terrabytes = 1,000,000 Gigabytes