Abstract: Apparatus and methods for operating a flash device characterized by use of Lee distance based codes in a flash device so as to increase the number of errors that can be corrected for a given number of redundancy cells, compared with Hamming distance based codes.

Abstract: A flash memory apparatus that may include a plurality of memory portions, and a controller operative to reserve for data retention purposes, for at least a first duration of time, only certain memory portions; allocate data, during said first duration of time, only to said certain memory portions, thereby to define a retired memory portion for said first duration of time; determine to copy data from a certain memory portion to a retired memory portion based upon a relationship between effective cycle counts of the certain memory portion and the retired memory portion, an effective cycle count of any memory portion is responsive to a number of erase-write cycles and to an effective duration of time the memory portion had available to recover from erase-write cycles; and copy the data from the certain memory portion to the retired memory portion.