The present invention discloses methods for storing data in a flash-memory storage device, the method including the steps of: receiving, by the device, primary data to be stored in the device and to be read from the device at a primary reading speed; storing at least part of the primary data only in fast pages in the device, wherein the fast pages are located in multi-level cells of the device; designating, by the device, secondary data to be read from the device at a secondary reading speed, wherein the secondary reading speed is slower than the primary reading speed; and storing at least part of the secondary data only in slow pages in the device, wherein the slow pages are located in the multi-level cells. Preferably, the method further includes the step of: moving the secondary data from a previously-stored area in the device to the slow pages.