LOG-BASED FTL AND OPERATING METHOD THEREOF

• US 20080201518A1
• Filed: 02/16/2007
• Published: 08/21/2008
• Est. Priority Date: 02/16/2007
• Status: Active Grant

• Current Assignee: Electronics and Telecommunications Research Institute
• Original Assignee: Electronics and Telecommunications Research Institute
• Inventors: Kim, Soo-Young, Jung, Sung-In
• Granted Patent: US 8,095,723 B2
• Time in Patent Office: Days
• US Class Current: 711/103
• CPC Class Codes: G06F 12/0246 in block erasable memory, e.g. flash memory

Abstract

A log-based FTL and an operating method thereof for improving performances of reading and writing operations to increase the lifetime of a flash memory. In the method, when a reading operation for an LBN and an LPN is requested, a PBN and a PPN corresponding to the LBN and the LPN are calculated with reference to a pagemap corresponding to the LBN. A physical page of a physical block corresponding to the PBN and the PPN is accessed so that a reading operation is performed. On the other hand, when a writing operation for the LBN and the LPN is requested, a PBN and a PPN for a free-page of a physical block last assigned for the LBN are calculated with reference to a blockmap. The physical page of the physical block corresponding to the PBN and the PPN is accessed, so that a writing operation is performed. The pagemap stores a PBN and a PPN, and the blockmap stores a PBN list and a PPN.

Claims

1. A method for address translation operation of a log-based FTL, the method comprising:

when a reading operation for an LBN (logical block number) and an LPN (logical page number) is requested, calculating a PBN (physical block number) and a PPN (physical page number) corresponding to the LBN and the LPN with reference to a pagemap corresponding to the LBN, and accessing a physical page of a physical block corresponding to the PBN and the PPN to perform a reading operation; and

when a writing operation for the LBN and the LPN is requested, calculating a PBN of a physical block last assigned and a PPN of a free-page of a physical block last assigned for the LBN with reference to a blockmap, and accessing the physical page of the physical block corresponding to the PBN and the PPN to perform a writing operation,

wherein the pagemap stores a PBN and a PPN corresponding to each of a plurality of LPNs subjected to the corresponding LBN, and the blockmap stores a PBN list of physical blocks sequentially assigned, and a PPN of a free-page of a physical block last assigned for the corresponding LBN, for each LBN.

2. The method according to claim 1, wherein the physical block last assigned is a block on which a writing operation is to be performed, and the free-page is a physical page to be stored data at next writing operation.

3. The method according to claim 1, wherein the performing of the reading operation comprises analyzing the physical blocks sequentially assigned for the LBN in reverse order of the PBN list to form a pagemap corresponding to the LBN when there is no pagemap corresponding to the LBN.

4. The method according to claim 3, wherein the forming of the pagemap comprises:

calculating all of the physical blocks sequentially assigned for the LBN with reference to the PBN list; and

calculating the LPN corresponding to the PPN and the PPN of each physical page for each physical block; and

calculating the PPN corresponding to each LPN for each physical block; and

confirming a PPN and a PBN of the physical block including the physical pages corresponding to a plurality of LPNs, respectively, subjected to the LBN while scanning the physical blocks in reverse order of the PBN list, and putting the conformation results together to form a pagemap corresponding to the LBN.

5. The method according to claim 4, wherein the calculating of the PPN corresponding to each LPN for each physical block comprises obtaining a PPN of a physical page on which a writing operation has been performed most recently when a plurality of physical pages correspond to one LPN.

6. The method according to claim 1, wherein the performing of the writing operation comprises:

updating a PBN and a PPN of a physical page of a physical block on which a writing operation has been performed on a pagemap corresponding to the calculated LBN; and

obtaining a new free-page from the physical block on which the writing operation has been performed, or assigning a new physical block and obtaining a free-page from the new physical block to update a PBN and a PPN of the free-page on the blockmap.

7. The method according to claim 6, wherein the updating of the PBN and the PPN of the free-page on the blockmap comprises:

updating the new free-page into the free-page of the physical block last assigned, when a new free-page is obtained from the physical block on which the writing operation has been performed; and

when there is no more free-page within the physical block on which the writing operation has been performed, assigning the new physical block and updating the new physical block into a last physical block of the list, obtaining a new free-page from the new physical block, and updating the new free-page into the free-page of the physical block last assigned.

8. The method according to claim 7, wherein the updating of the PBN and the PPN of the free-page on the blockmap further comprises:

when there is no free-page within the physical block on which the writing operation has been performed, and a maximum number of the physical blocks are assigned for the calculated LBN, assigning the new physical block, merging the new physical block with the physical blocks assigned for the calculated LBN, and updating the new physical block and a PBN and a PPN of the free-page on the blockmap.

9. The method according to claim 8, wherein the merging comprises:

when there is no free-page within the physical block on which the writing operation has been performed, and a maximum number of the physical blocks are assigned for the calculated LBN, assigning the new physical block;

dividing the number of physical pages subjected to the physical block by the maximum number to calculate a merge reference value;

selecting the physical block of the physical blocks sequentially assigned for the LBN that has valid pages less than the merge reference value;

copying the valid pages of the selected physical block to a free-page of the new physical block, and performing an erasing operation on the selected physical block; and

releasing an assigned state between the selected physical block and the LBN, setting the new physical block to the physical block last assigned for the LBN, and setting a free-page of the new physical block to the free-page of the physical block last assigned.

10. A log-based flash translation layer comprising:

a plurality of pagemaps generated to correspond to a plurality of LBN(logical block number)s, respectively, to store PBN(Physical block number)s and PPN(Physical Page number)s corresponding to respective LPN(logical Page number)s subjected to the corresponding LBNs;

a blockmap for storing a PBN list of physical blocks sequentially assigned, and a PPN for a free-page of a physical block last assigned for the corresponding LBN, for each LBN; and

a processor for performing an address translation operation with reference to the pagemap during a reading operation, and performing an address translation operation with reference to the blockmap during a writing operation.

11. The log-based flash translation layer according to claim 10, wherein the physical block last assigned is a block on which a writing operation is to be performed, and the free-page is a physical page storing no data.

12. The log-based flash translation layer according to claim 10, wherein the processor has functions of dividing a logical sector number provided by a file system by the number of logical blocks to obtain an LBN and an LPN, calculating a PBN and a PPN corresponding to the LPN with reference to the pagemap corresponding to the LBN, and accessing the physical block and the physical page having the calculated PBN and PPN during a reading operation.

13. The log-based flash translation layer according to claim 12, wherein the processor further has a function of analyzing the physical blocks sequentially assigned for the LBN in reverse order of the PBN list to confirm a PPN and a PBN of the physical block including the physical pages corresponding to a plurality of LPNs, respectively, subjected to the LBN, and putting the confirmation results together to form a pagemap corresponding to the LBN when there is no pagemap corresponding to the LBN during a reading operation.

14. The log-based flash translation layer according to claim 10, wherein the processor has functions of dividing a logical sector number by the number of logical blocks to obtain an LBN, calculating a PBN and a PPN corresponding to the LBN with reference to the blockmap, and accessing a physical page of the physical block having the calculated PBN and PPN during a writing operation.

15. The log-based flash translation layer according to claim 14, wherein the processor further has a function of updating the physical block and a PBN and a PPN of the physical page on which a writing operation has been performed on the pagemap corresponding to the LBN.

16. The log-based flash translation layer according to claim 14, wherein the processor further has a function of obtaining a new free-page from the physical block on which the writing operation has been performed, or assigning a new physical block and obtaining a free-page from the new physical block to update a PBN and a PPN of the free-page on the blockmap.

17. The log-based flash translation layer according to claim 16, wherein the processor further has a function of, when there is no free-page within the physical block on which the writing operation has been performed, and a maximum number of the physical blocks are assigned for the LBN, assigning the new physical block, merging the new physical block with the physical blocks assigned for the LBN, and updating the new physical block and a PBN and a PPN of the free-page on the blockmap.