GC & Write Amplification

Garbage collection

• FTL fills incoming data into the erased nand-block

• Overwriting the same logical block goes to new erase nand block ( copy on write)

• No free space => Do GC

• Copy valid pages

• Copy done !!

• Erase 5 blocks, GC done

• Performance degradation by GC

Write amplification

• Write amplification = ( Data written to the flash memory) / ( Data written by host )
• WA KEY = Garbage collection Map(FTL-meta) update Wear-leveling