The information can be retrieved from Regular RDBMS technologies put the information on spinning plates of iron (hard disks). The information is stored in electronic memory, which is some 50x faster (depending on how you calculate). It stores a copy on magnetic disk, in case of power failure or the like. Also to add in, most SAP systems have the database on one system and a calculation engine on another, and the information is passed between them. With HANA, this all happens within the same machine.