spare area nand flash

[darioelet]

Salve a tutti, ho un dubbio che non riesco a risolvere:
nelle moderne memorie nand flash non è possibile scrivere pagine in maniera random e neanche è permesso il partial page programming... però mi sovviene un dubbio: per marcare un blocco come dirty come faccio se tutte le pagine sono state scritte? ho pensato di poter scrivere almeno nella spare area dell'ultima pagina... ma non ho trovato conferma su internet, qualcuno potrebbe illuminarmi?

[giorgio25760]

Blocks can be marked as bad and new blocks allocated using two general methods:
• Skip block
• Reserve block
Skip Block Method
In the skip block method the algorithm creates the bad block table and when the target
address corresponds to a bad block address, the data is stored in the next good block,
skipping the bad block.
When a bad block is generated during the lifetime of the NAND Flash device, its data is
also stored in the next good block. In this case, the information that indicates which
good block corresponds to each developed bad block must also be stored in the NAND
Flash device.
Reserve Block Method
In the reserve block method, the bad block table is created in the same manner as
described in Figure 2. In this method bad blocks are not skipped but replaced by good
blocks by redirecting the FTL to a known free good block. For that purpose, the bad block
management software creates two areas in the NAND Flash: The user addressable block
area and the reserved block area as shown in Figure 3.
The FTL can use the user addressable block area to store data whereas the reserved
block area is only used for bad block replacement and to save the bad block table, which
also keeps track of the remapped developed bad blocks.
To define these two areas, determine the start address and the size of the reserved area.
The size may either be given by the user or imposed by the bad block management
software (for Micron NAND Flash devices, the maximum number of blocks that may
become bad during the device's lifetime is 2% of the total, and as a result the same
number of blocks are commonly reserved).
Each time the FTL writes a logical sector, it calculates the physical address of the block to
which it will write. Then, before the FTL starts writing, the bad block management
software checks whether the block is bad or not. If it is bad, it returns the address of the
good block to which the sector is remapped. If the block becomes bad during the NAND
Flash lifetime, the bad block management software remaps the bad block and copies the
data it contains to the block that will replace it.
Bad block management is completely transparent to the FTL. For the FTL it is as if the
data are written to the same address.