Physical Storage Media(Cont.) Flash memory Data survives power failure Data can be written at a location only once,but location can be erased and written to again Can support only a limited number(10K-1M)of write/erase cycles. Erasing of memory has to be done to an entire bank of memory Reads are roughly as fast as main memory But writes are slow(few microseconds),erase is slower Widely used in embedded devices such as digital cameras, phones,and USB keys Database System Concepts-6th Edition 10.5 ©Silberschat乜，Korth and SudarshanDatabase System Concepts - 6 10.5 ©Silberschatz, Korth and Sudarshan th Edition Physical Storage Media (Cont.) Flash memory Data survives power failure Data can be written at a location only once, but location can be erased and written to again  Can support only a limited number (10K – 1M) of write/erase cycles.  Erasing of memory has to be done to an entire bank of memory Reads are roughly as fast as main memory But writes are slow (few microseconds), erase is slower Widely used in embedded devices such as digital cameras, phones, and USB keys