Data cache method used in NAND FLASH

Abstract

The invention provides a data cache method used in NAND FLASH. The method comprises following steps: first, a cache region cache is divided into a block-level cache and a page-level cache; then, when read-and write is performed on data, if current data exists in the block-level cache or the page-level cache, then data read-and write is directly completed; if current data does not exist in the block-level cache or the page-level cache, then data is read from the FLASH or free space in the data cache region is distributed to the current data and data is written in the FLASH; if there is no free space, a substitution block is determined through a substitution algorithm and data in the substitution block is written in the FLASH; finally, the substitution block is released, new data is written in, and then data cache is completed. By means of the combination of block cache and page cache, the cache hit ratio of random read-and-write access is increased; a efficient substitution algorithm is provided; the size of cache mapping table is reduced and space utilization rate of the cache region is increased; the method has good use value.

Description

technical field [0001] The invention relates to a FLASH storage technology, in particular to a data cache method for NAND FLASH. Background technique [0002] At present, relatively mainstream SSDs are all based on NAND FLASH media. SSDs include main control, flash memory, cache, and firmware. Due to the structural characteristics of NAND FLASH, the basic unit of erasing operation is block, while the basic unit of reading and writing is page, and the smallest unit of reading and writing data from host to SSD is sector. Therefore, FLASH needs to erase the block before writing data, and copy other valid data to the free block before erasing, and then write other valid data and rewritten data into the block after the erase is completed. [0003] In the traditional read and write technology, the host generally uses the following method to write data to the SSD: the host first writes the data into the cache through the storage array, and then writes the data to the SSD after the...

AI Technical Summary

Problems solved by technology

However, these methods still have the problem of write penalty and write amplification. Sectors or pages are used as the internal read and write granularity of SSD. The page filling process increases the cache management mapping table space consumption, reduces the cache hit rate, and also increases garbage. The cost of recovery can not effectively improve the write performance of SSD system

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