Wear levelling
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EEPROM and flash memory media have individually eraseable segments, each of which can be put through a finite number of write cycles before failing (anywhere between 104 to 106 cycles, for example, for NAND flash devices).
Wear levelling generally involves arranging data so that erasures can be rotated evenly across the medium, thus prolonging the service life of the memory device. It can be performed by a built-in microcontroller or by a special-purpose file systems such as JFFS or JFFS2.
Storage interfaces like DiskOnChip allow flash memory devices to emulate regular IDE disks but in themselves do not perform wear levelling. This makes them unsuitable for general-purpose read-write storage with conventional file systems like FAT, ext2 or NTFS.