Storage system with second-level cache structure and reading/writing method

Abstract

The invention provides a storage system with a second-level cache structure. The storage system comprises a host internal memory and a solid state hard disk, wherein the solid state hard disk comprises a main control chip, an NAND chip and an MRAM; the host internal memory comprises a read cache; and the MRAM comprises a write cache. The invention furthermore provides a reading/writing method which adopts the storage system with the second-level cache structure. According to the second-level cache structure and the reading/writing method which adopts the second-level cache structure, the reading operability is better; the MARM is used as the write cache, so that the data writing speed is greatly improved while the security of the data under the condition of unexpected outage is ensured; by using the read cache in the host internal memory, the limited MRAM space can be used as the write cache as much as possible, so that the cost is optimum and an expensive outage protection system is saved; and by using the MRAM as the write cache, the write frequency of the NAND is decreased, so that the NAND is protected and the service life of the NAND is prolonged. According to the storage system and the reading/writing method, a scheme with good cost-benefit ratio is provided.

Description

technical field [0001] The invention relates to a solid-state hard disk, in particular to a storage system with a secondary cache structure and a read-write method. Background technique [0002] Currently, the development of NAND flash memory technology has promoted the SSD industry. Such as figure 1 As shown, high-speed serial interfaces such as SATA, PICe and other technologies are used between the SSD and the host. The interior consists of a set of NAND chips used to store data, DDR DRAM (memory) used to support calculations and cache data, and a main control chip (SSD Controller). Sometimes a power failure protection system is also required. [0003] NAND is a storage device that reads and writes in blocks. The smallest readable unit is called a page, and the smallest erasable unit is called a block. A block is often composed of many pages. After the block is erased, the Pages can be written individually. Write operations are slow, much slower than read operations, ...

AI Technical Summary

Problems solved by technology

However, the introduction of the write cache creates a new problem: once a power failure occurs, the content in the DRAM cache that has not been written to the NAND will be lost, causing the system to lose data or even damage the entire file system

Using a large amount of MRAM will also significantly increase the cost of the product

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