基于PCIE接口混合存储系统的设计与实现

华中科技大学

硕士学位论文

基于PCIE接口混合存储系统的设计与实现

姓名：钟德懿

申请学位级别：硕士

专业：计算机技术

指导教师：周功业

2011-05-27

华中科技大学硕士学位论文

摘要

FLASH存储介质的出现已有20多年的历史，随着设计和的工艺改进，以FLASH 为存储介质的存储器得到了广泛的应用。近几年，FLASH存储器已经从传统的嵌入式领域扩大到了PC、服务器领域。相变存储器（PCRAM）是一种新型非易失性存储器技术，近年来随着材料科学的发展及制作工艺的进步，PCRAM取得了重大突破。PCRAM作为一种新型非易失性存储器，其多种性能指标优于FLASH 存储器。

考虑现有的技术条件，结合 FLASH成熟的应用技术和PCRAM的优点，设计了一种新型的混合存储器。针对这种混合存储器的特点，参考一些比较成熟的文件系统，设计并实现了一种新的文件系统。该文件系统将元数据、用户数据修改后的更新数据与用户数据相分离，并将元数据、更新数据存储在PCRAM，用户数据存储在FLASH上。对于FLASH中的每个数据块，在PCRAM中都有一定容量空间与之对应。FLASH中的数据被修改后写入与之对应的PCRAM中。超级块用于对文件系统的基本描述，索引位图和数据页位图是一些联系的位，它们用于描述某一索引节点和数据页是否被使用。在新的文件系统中，索引节点域包含了描述和管理每个文件的索引节点。而数据块信息域的另一作用是用于管理FLASH上的块。

基于页映射算法给出了新的FLASH 转换层（FTL）地址映射算法，并在以下三方面进行了改进：一是使用PCRAM存储FTL元数据，例如页映射表、物理块信息、坏块信息等。这能有效解决原来的页映射算法中的较大的内存开销及重建映射表的时间开销问题；二是新的FTL算法支持逻辑页删除功能，这将减少垃圾回收的开销；三是新的管理方式，通过添加保留块可用于防止当存储器接近用尽时频繁产生的合并操作。针对混合存储器，设计并实现了相应的PCIE接口驱动程序和Linux 块设备驱动程序。

关键词：相变存储器，驱动程序，文件系统，元数据，FLASH转换层

华中科技大学硕士学位论文

Abstract

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.

Keywords: PCRAM, Driver, Files system, Metadata,FTL