Brief analysis of the small disk capacity change

In fact, the reason is simple:

U disk when writing data, U disk inside the chip needs at least a physical block "blocks" as a swap block to use, this is because the U disk memory write operation is very special, you must first erase before you can write data, and the smallest unit is erased is a physical block, but the smallest unit of writing data is indeed a page " Page ".

U Disk Memory storage unit, a physical block contains a number of physical pages, so write data, need to have an empty, and can use the exchange quickly to store the data do not need to be erased. Because of the memory charge and discharge characteristics of u disk, it has a physical limit on the number of reads and writes. Under normal circumstances, manufacturers

will be inside the U disk to do a number of read and write count, when a flash memory chip of a physical storage block reached the maximum number of reads and writes, the block area will be set to no longer use the area, so, in the extreme frequency of the use of U disk in the case, the U disk capacity may become less and less.

　　The current market on the U disk products include two categories:

1. No Reserve buffer space of u disk: Because there is no space reserved, u disk in reading and writing when the exchange of fast loss is very large, so will appear to use the longer U disk capacity for a long time smaller and less.

2. There are reserved buffer space of u disk: The factory in the design time has reserved part of the physical block, such as the selection of 1024 physical blocks of 1000 as data storage use, the remaining 24 physical blocks (including bad blocks) as a buffer swap block part. Each time you plug in a U disk, the logical address and physical address of the storage unit need to be heavy

The new control, the Exchange block is not a fixed block, so that each physical block to read and write the probability of almost the same, do not appear which physical block prematurely damaged phenomenon. To reserve the buffer space of the U disk, the basic will not appear less and less capacity.