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 Cost per unit of storage roughly similar to main memory Widely used in embedded devices such as digital cameras Is a type of EEPROM(Electrically Erasable Programmable Read-Only Memory) Database System Concepts-5th Edition,Oct 23,2005. 11.5 ©Silberschat乜，Korth and SudarshanDatabase System Concepts - 5 11.5 ©Silberschatz, Korth and Sudarshan th Edition, Oct 23, 2005. 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 Cost per unit of storage roughly similar to main memory Widely used in embedded devices such as digital cameras Is a type of EEPROM (Electrically Erasable Programmable Read-Only Memory)