A New Hybrid Storage System Of Pcram And Nand Flash Based On PCIE Interface

With the design and process improvements, flash storage,which has been emerged more than 20 years, has been widely used. In recent years,flash memory has been expanded from the traditional embedded area to the area of the PC and server. Phase Change Random Access Memory(PCRAM),a new non-volatile memory technology, achieved a major breakthrough.PCRAM is better than flash memory in many aspects.Under the conditions of the existing technology,we design a new hybrid memory combined with the the application of mature technologies of flash and the advantage of the PCRAM. We also design a new file system for the hybrid memory. Metadata,the modified user data,user data are separated in this file system. The former two are stored in the PCRAM, the latter one is stored in flash.For each block in the FLASH have a certain volume of space in the corresponding in PCRAM. The modified data writes in the corresponding place in the PCRAM. In the new file system,inode filed contains the description and management of each file's inode, the another role of the data block information is to manage the block in the flash.Based on the page mapping algorithm, we design the new flash translation layer address mapping algorithm which have been improved in the following three aspects.First,we use the PCRAM to store FTL metadata, For example, mapping table pages, physical pieces of information, bad block information.Second,the new FTL algorithm supports logical page delete function. It will reduce the cost of garbage collection.Third, New management style, by adding the reserved block,can be used to prevent frequent operation when the memory is close to the exhaustion. I also design and implement the corresponding PCIE interface driver and the Linux block device driver.