基于RAID5的闪存固态盘阵列关键技术研究

发布时间：2018-06-20 09:32

  本文选题：SSD + RAID5控制器　； 参考：《国防科学技术大学》2013年硕士论文

【摘要】：随着数字设备的普及和网络的飞速发展,当今世界已经成为数据的世界,数据存储系统面临着极大的挑战。当前应用不仅需要更大的存储容量,在延迟、带宽、可靠性、能耗等方面也对存储系统提出了更高的要求。传统磁盘设备因其内部机械装置的限制,已经成为大规模存储系统的主要性能瓶颈。基于闪存的SSD(Solid State Drive)以其优异的性能、非易失和低功耗等特点,已经在高端系统中得到广泛的应用。但是,闪存存在寿命有限的缺陷,当闪存应用到大规模存储系统中时存在可靠性方面的问题。RAID(Redundant Arrays of Independent Disks)是一种传统的提高存储可靠性的方案。利用RAID技术构建大规模闪存阵列,既可以增大闪存存储系统的容量,提高性能,又能保证可靠性。本文重点研究基于RAID5的SSD阵列,根据RAID的特性优化了SSD的内部结构,并根据闪存的特性改进了RAID5的控制逻辑,通过两者的结合延长RAID5阵列中SSD的寿命。文章的主要工作和创新点如下:首先,针对闪存寿命有限的问题,提出了一种能够感知RAID5校验信息的PA-SSD(Parity Aware-SSD)结构,该结构在SSD内部合理布局RAID5产生的校验信息,减少SSD内部产生的额外写请求,从而延长SSD的寿命。另外,该结构在SSD控制器内部提出了基于权重值的写缓存替换策略,并优化了FTL(Flash Translation Layer)的地址映射策略和损耗均衡策略。其次,改进了RAID5控制器的内部结构。针对程序中数据的局部性,在RAID5控制器内部增加写缓存,减少写入SSD的数据量;针对校验信息更新频繁的问题,设置数据缓存和部分校验缓存,分别接收从写缓存替换出的用户数据和校验信息,减少校验信息更新时产生的I/O请求,延长SSD的寿命。最后,实现了基于RAID5的SSD阵列模拟器,并基于该模拟器评估了本文提出的PA-SSD结构和改进的RAID5控制器。实验结果表明,PA-SSD平均能够使校验信息的写入量减少26%,闪存芯片的擦除次数降低17%,闪存内部的数据迁移量降低32%。另外,改进的RAID5控制器能够使整个阵列的写请求数降低66%,写延迟降低44%。
[Abstract]:With the popularity of digital devices and the rapid development of the network, the world has become a data world, data storage system is facing a great challenge. Current applications not only need larger storage capacity, but also put forward higher requirements for storage system in terms of delay, bandwidth, reliability, energy consumption and so on. Traditional disk devices have become the main performance bottleneck of large-scale storage system because of the limitation of internal mechanical devices. Flash memory based solid State driven has been widely used in high-end systems due to its excellent performance, non-volatile and low power consumption. However, flash memory has the limitation of limited lifetime. When flash memory is applied to large scale storage system, there is a reliability problem. Raid undant Arrays of Independent disks) is a traditional method to improve storage reliability. Using raid technology to construct large scale flash memory array can not only increase the capacity of flash memory system, but also improve the performance and reliability. This paper focuses on the SSD array based on RAID5, optimizes the internal structure of SSD according to the characteristics of raid, improves the control logic of RAID5 according to the characteristics of flash memory, and prolongs the life of SSD in RAID5 array by combining the two. The main work and innovations of this paper are as follows: firstly, in order to solve the problem of limited flash memory life, a PA-SSD-Parity Aware-SSD-based structure is proposed, which can sense the verification information of RAID5. Reduces additional write requests generated within the SSD, thereby prolonging the life of the SSD. In addition, the structure proposes a write-cache replacement strategy based on weight value in the SSD controller, and optimizes the address mapping strategy and loss equalization strategy of FTL / Flash Translation layer. Secondly, the internal structure of RAID5 controller is improved. Aiming at the locality of data in the program, adding write cache inside RAID5 controller, reducing the amount of data written to SSD, setting up data cache and partial check cache for frequent updating of checkout information. The user data and verification information replaced from the write cache are received respectively to reduce the I / O requests generated when the checkout information is updated and to prolong the life of SSD. Finally, the SSD array simulator based on RAID5 is implemented, based on which the PA-SSD structure and the improved RAID5 controller are evaluated. The experimental results show that PA-SSD can reduce the write amount of verification information by 26 times, erase the memory chip by 17 times, and reduce the internal data migration of flash memory by 32 parts on average. In addition, the improved RAID5 controller can reduce the number of write requests and write delay by 66% and 44% respectively.
【学位授予单位】：国防科学技术大学
【学位级别】：硕士
【学位授予年份】：2013
【分类号】：TP333
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本文编号：2043808