FTL Technology and BAST Scheme

6 May

If you find the offset in the data block has been occupied (ie, write) the last one of the write operation FTL write a given sector in the same offset a free block allocation from the free block list. Next, the offset found in all sectors written outside the sector data block is copied to a free block. Finally, FTL erase blocks of data, and to return to the free block list.
Whenever a collision between the current write and write, you need a large number of sectors copy and erase. Series such as operation is called a merge operation. In order to solve this problem, the many FTL art has been provided the bast plan is well-known fact that the best the FTL technology [1]. When a collision occurs, the bast plan is written to the temporary storage of data blocks, thereby reducing the number of combined business, ie log. In the following, we use an example to be described in detail BAST scheme.
Let the number of sectors per block is 4 and the number of log block two. The top left of a sequence of writes issued from the file system above the center of the upper right part of the block-level and page-level address mapping table, normally kept in the SRAM flash. In the first write operation is referred to as the the BAST algorithm of data block 10, block-level logic block 1 (= 4 4) address mapping table. Then, it is stored in data block 10 at offset 0 (= 4 mod 4) a given sector. In the case of the second write operation, the same thing, the first time a write operation is complete. In the case of collision occurs in the third write operation, the data block 10, so that the industry is to write a log block in the first offset (i.e., PBN = 20), to be allocated to the logical block 1 log The block list. In the fourth case of write operation, the sector is offset existing log block to the next empty. The rest of the write operation will cause the second log block (i.e., PBN = 30) and sector address mapping table of FIG.


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