The LazyFTL Structure

9 Apr

The LazyFTL entire flash memory is divided into four parts: data block area (DBA), the the mapping block area (MBA), the cold block area (CBA), update the block area (UBA). All of these components except the MBA is used to store user data. DBA page tracking page-level mapping table called the global mapping table (GMT). GMT in units of pages, and stored in the MBA. A small cache LRU algorithm or the like retained in the SRAM provide a high efficiency of the most frequent reference GMT 4accessed. Secondary table named Global Mapping directory (GMD) stored in the SRAM

And maintain all valid mapping the physical location of the page GMT. The use of CBA to adapt to the cold block UBA is used to accommodate as update block name.

The main difference between the original and LazyFTL

Page-level FTL scheme [3,12] two small partition LazyFTL reserves, CBA and enlightened postponed modify cation GMT cause a write request or a valid page action. CBA and enlightened the total size is relatively small compared with the entire flash memory, the like the LBA mixed FTL plan, another page-level mapping table, which is called the updated mapping table (UMT) is built on these two areas. Urban rail transit can be achieved as a hash table or binary search tree, to support efficient Insert, delete, modify, and reference. The number of entries in the UMT is rather small, therefore, these operations do not introduce too much overhead.

Enlightened block called this profile block (CUB) are used to process a write operation. When the cubs over-flow, another free block allocation, and become the new

CUB. Similarly, in the current the the CBA process moves data page through the cooling block (CCB). As a matter of fact, LazyFTL the cold filler block the CBA and fill Toowoomba updating blocks in the same manner. In other words, the relative size of the CBA and enlightened can be adjusted dynamically. If the rate of increase in the thermal data conversion costs in an open block (see 4.1) will decline more slowly UBA will expand. If the space utilization increases, China Construction Bank will fill faster than CUB CBA enlarge. In this manner, adjusted LazyFTL itself automatically to the type of access mode.

It is necessary to mention that, this is also possible to split the CBA and enlightened into smaller functional areas, such as the last [18]. However, we decided to keep the design as simple as possible, because the current design is quite effective, and there is not enough space to improve performance. We are also maintained in the SRAM, two bitmaps updated logo and flag invalid two bitmaps flag CBA and enlightened state of all the pages. Update flag indicates whether it needs to be updated to the appropriate page conversion Beijing time each invalid flag indicates whether or not the target page corresponding the GMT entry point needs failure.


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