固态硬盘SSD性能分析及RAID 0方案设计

针对SATA II接口300 MB/s的最大极限传输速度,为突破其瓶颈,提出了一种基于固态硬盘的RAID 0阵列存储方案,使得固态硬盘在SATA II接口下的传输性能达到更高。首先使用两片英睿达CRUCIAL容量为256 GB的SSD固态硬盘单独挂载在SATA II接口下测得传输性能;然后设置主板RAID模式,将其组建RAID得到Volume0,同样测得传输性能;最后通过对比测试,RAID 0 SSD整体的持续读写性能明显优于单盘SSD。性能测试结果表明,SSD在数据的读取写入、突发传输速率等方面都远优于传统机械硬盘,RAID 0更能使得SSD的性能达到最大,突破SATA II接口的峰值传输速度。     

PMC第二代SSD缓存解决方案

日前,PMC-Sierra公司宣布推出配备maxCache 2.0SSD Caching(固态硬盘缓存)功能的Adaptec 6Q系列控制器,有效加快数据中心和云计算的运行。AdaptecmaxCache 2.0采用了智能的经验路径(learned-path)算法,利用固态硬盘(SSD)来缓存频繁存取的数据,显著提升硬盘阵列的性能。PMC第二代SSD解决方案     

性能为王 英特尔730系列固态硬盘抢先评测

英特尔推出了全新730系列的玩家级固态硬盘,上面印有一个骷髅的形象,他们显然没有辜负这个冷酷杀手的形象。我们拿到了一对480GB的SSD硬盘,并组成了一个RAID O的双SSD阵列,以对其性能进行基准评测。正如你知道的,RAID O是电脑发烧友们用相对便宜的多块硬盘组成一个高性价比硬盘阵列组的最佳方案,这将使性能达到甚至超过一个价格昂贵、容量巨大的硬盘。从理论上讲,这种方式会得到原固态硬盘接近增加一倍的性能提升,但是因为     

MuLe-RAID:面向大容量高性能SSD的层次化RAID

利用RAID机制构建基于闪存的SSD可以提高SSD的性能和可靠性,但是随着SSD容量的增大,传统的单层RAID结构容易造成控制器的瓶颈.针对这个问题,提出了一种新的RAID策略——MuLe-RAID(Multiple Level RAID),给出了详细架构和设计细节.其采用层次化RAID结构,设置多个控制器,在每一层的控制器中实现不同粒度的损耗均衡管理,在保证SSD损耗均衡的同时,通过减轻控制器的瓶颈提高了SSD的性能.为了提高可靠性,MuLe-RAID采用了冗余机制,能够达到RAID5的容错级别.通过模拟实验测试表明,在大容量SSD中,相比传统RAID,MuLe-RAID在保证损耗均衡的基础上有大约30%的性能提升.     

GC-RAIS:一种基于垃圾回收感知的固态盘阵列

垃圾回收操作会显著影响固态盘的性能,进而导致固态盘阵列的性能波动.为此,提出一种基于垃圾回收感知的磁盘阵列(GC-RAIS),充分利用固态盘的高随机读特性和固态盘阵列中的热备份盘,以减轻垃圾回收操作对固态盘阵列性能波动的负面影响.当固态盘阵列中某个固态盘正在处理垃圾回收操作时,对于到达该固态盘的读请求采用重构方式处理,即读取同一条带上其他固态盘上的数据重构得到,而对于到达该固态盘的写请求则将写数据临时存放在热备盘中,并更新相应的校验信息.当垃圾回收过程结束后,将被重定向的写数据写回到正确的固态盘中.仿真实验结果表明相对局部垃圾回收LGC策略和全局垃圾回收GGC策略,GC-RAIS分别减少用户I/O请求的平均响应时间达55％和25％.     

LSI发布新一代基于6Gb／s SAS技术的高性能RAID控制卡

2009年7月29B,LSI公司宣布推出基于6Gb,sSAS技术的新一代高性能MegaRAID SATA＋SASRAID控制器oMegaRAID9200系列控制器拥有创新的6Gb,sSAS产品特性,并且支持SATA、SAS和固态硬盘（SSD）,可为中小企业提供卓越的RAID性能以殛内部和外部存储的扩展性能。     

先软后硬 为SSD硬盘“延寿”

SSD固态硬盘虽然具备极致的读写速度,但闪存颗粒存在写入次数的极限值,因此SSD的寿命总会随频繁的使用而折损。如果你想尽可能延长SSD的使用寿命,不妨从软硬两个方面下手优化。可读不可写的SSD SSD的物理特性决定了其怕写(入)不怕读(取),想延长SSD寿命自然就要落实到如何尽可能减少硬盘的写入数据量。而影响硬盘写入数据的操作主要在于硬盘索引、预读取、系统还原和Windows事件记     

文萃开心辞典

Matrix-RAIDMatrix-RAID是一种全新的磁盘冗余阵列标准,目前被广泛采用的RAID标准有RAID5、RAID0、RAID1和RAID0 1等,其中RAID0是最简单的一种形式,它可以提供更多的磁盘空间和更好的性能,RAID1又称磁盘镜像,即每个磁盘都有一个对应的镜像盘,这样就可以最大限度地保证系统数据的可修复性。若想同时建立RAID0和RAID1阵列,用户至少要拥有四个硬盘,而Matrix-RAID技术在两块硬盘上就可以同时建立RAID0和RAID1阵列,它能把硬盘分为RAID0和RAID1两个逻辑分区,从而让硬盘同时获得高速度和高稳定性。由于MatrixRAID需要…     

SSD固态硬盘存储系统的优化与测试探究

计算机技术飞速发展,使得人们的生产生活给信息存储提出更高要求,SSD固态硬盘凭借体积小、耗能低、质量轻、读写速度快等优点被广泛应用在信息存储中,有关SSD固态硬盘存储系统的优化与测试也因此引起了人们的重点关注.本文对固态硬盘理论知识分析的基础上,运用相关方法对固态硬盘存储系统进行优化,结果表明优化方法切实可行,固态硬盘性能提升明显,可为实际的优化工作提供参考.     

PMC12Gb／sSAS控制器＋扩展器方案在性能以及密度上为云存储和分层存储再创新纪录

致力于存储网络、光网络以及移动网络半导体解决方案创新的PMC-siem公司（以下简称“PMC”;纳斯达克代码：PMCS）近日宣布,推出其12Gb／sSAS协议控制器、片上RAID（RoC）控制器和扩展器。使服务器和网络存储拥有突破性的性能和可扩展性。高性能固态硬盘（SSD）提供的每秒输入输出次数（IOPS）比传统的硬盘驱动器（HDD）高达100倍,这对存储控制器的规格提出了更高层级的要求。PMC12Gb／sSAS控制器拥有优化的性能,不仅可以满足这一需求还可以释放固态硬盘的全部潜能。另外,PMC12Gb／s解决方案拥有业界最高端口数的扩展器,能够提供比业界同类解决方案多40％的硬盘连接,助力企业和云数据中心实现新一代可扩展的分层存储。     

A high-performance and endurable SSD cache for parity-based RAID

Solid-state drives (SSDs) have been widely used as caching tier for disk-based RAID systems to speed up dataintensive applications. However, traditional cache schemes fail to effectively boost the parity-based RAID storage systems (e.g., RAID-5/6), which have poor random write performance due to the small-write problem. What’s worse, intensive cache writes can wear out the SSD quickly, which causes performance degradation and cost increment. In this article, we present the design and implementation of KDD, an efficient SSD-based caching system which Keeps Data and Deltas in SSD. When write requests hit in the cache, KDD dispatches the data to the RAID storage without updating the parity blocks to mitigate the small write penalty, and compactly stores the compressed deltas in SSD to reduce the cache write traffic while guaranteeing reliability in case of disk failures. In addition, KDD organizes the metadata partition on SSD as a circular log to make the cache persistent with low overhead.We evaluate the performance of KDD via both simulations and prototype implementations. Experimental results show that KDD effectively reduces the small write penalty while extending the lifetime of the SSD-based cache by up to 6.85 times.     

Exploiting flash memory characteristics to improve performance of RAIS storage systems

Redundant array of independent SSDs (RAIS) is generally based on the traditional RAID design and implementation. The random small write problem is a serious challenge of RAIS. Random small writes in parity-based RAIS systems generate significantly more pre-reads and writes which can degrade RAIS performance and shorten SSD lifetime. In order to overcome the well-known write-penalty problem in the parity-based RAID5 storage systems, several logging techniques such as Parity Logging and Data Logging have been put forward. However, these techniques are originally based on mechanical characteristics of the HDDs, which ignore the properties of the flash memory. In this article, we firstly propose RAISL, a flash-aware logging method that improves the small write performance of RAIS storage systems. RAISL writes new data instead of new data and pre-read data to the log SSD by making full use of the invalid pages on the SSD of RAIS. RAISL does not need to perform the pre-read operations so that the original characteristics of workloads are kept. Secondly, we propose AGCRL on the basis of RAISL to further boost performance. AGCRL combines RAISL with access characteristic to guide read and write cost regulation to improve the performance of RAIS storage systems. Our experiments demonstrate that the RAISL significantly improves write performance and AGCRL improves both of write performance and read performance. AGCRL on average outperforms RAIS5 and RAISL by 39.15% and 16.59% respectively.     

阵列矩阵RAID50研究——容量聚合与全并发策略

提出了一种跨多阵列通道的海量存储RAID50模型,通过采取多阵列卡的RAID0分条和阵列卡上多磁盘RAID5分条和校验的二级并发的数据组织与分块方式,以扩展块（大小等于阵列卡上的一个RAID5校验组）作为Cache和阵列之间数据交换的单位,实现了将阵列矩阵中所有磁盘的容量聚合及全并发访问。设计了该模型逻辑卷管理的最佳适配算法及二级地址映射算法。理论分析与实验结果表明：该策略将I/O响应时间降到了最低,且获得了与阵列通道数线性相关的逻辑卷容量和I/O性能。     

利用DCMT来解决RAID5的小写问题

在盘阵中，RAID5利用校验信息来提高数据的可靠性。由于要维护校验信息，带来了小写问题，影响了系统的整体性能。本文在AFRAID方法的基础上，提出了一种基于动态缓存标志表（DCMT）的提高RAID5性能的方法。该方法在保证RAID5磁盘数据特征的前提下，用较小的代价就可以大大缩短响应时间，提高系统整体性能。     

CSWL: Cross-SSD Wear-Leveling Method in SSD-Based RAID Systems for System Endurance and Performance

Flash memory has limited erasure/program cycles.Hence,to meet their advertised capacity all the time,flashbased solid state drives(SSDs) must prolong their life span through a wear-leveling mechanism.As a very important part of flash translation layer(FTL),wear leveling is usually implemented in SSD controllers,which is called internal wear leveling.However,there is no wear leveling among SSDs in SSD-based redundant array of independent disks(RAIDs) systems,making some SSDs wear out faster than others.Once an SSD fails,reconstruction must be triggered immediately,but the cost of this process is so high that both system reliability and availability are affected seriously.We therefore propose cross-SSD wear leveling(CSWL) to enhance the endurance of entire SSD-based RAID systems.Under the workload of random access pattern,parity stripes suffer from much more updates because updating to a data stripe will cause the modification of other all related parity stripes.Based on this principle,we introduce an age-driven parity distribution scheme to guarantee wear leveling among flash SSDs and thereby prolong the endurance of RAID systems.Furthermore,age-driven parity distribution benefits performance by maintaining better load balance.With insignificant overhead,CSWL can significantly improve both the life span and performance of SSD-based RAID.     

磁盘阵列校验信息的放置策略

廉价磁盘冗余阵列（ＲＡＩＤ）采用许多小的廉价磁盘来代替大容量昂贵的磁盘，以取得更高的性能和更低的功耗。本文介绍了ＲＡＩＤ－５级磁盘阵列中校验信息的八种不同的分布策略，即奇偶校验信息的放置策略，并从几个不同的应用情况对不同的放置策略进行了研究，结论是不同的奇偶校验信息放置策略对磁盘阵列的Ｉ／Ｏ读写性能有很大的影响。     

一种优化的小写操作RAID6算法

提出一种优化的小写操作RAID6算法XP-Code。该算法按对角线和逆对角线划分校验组,每个校验组中有一个校验块和N-2个数据块,校验块均匀分布在2条主对角线上。由于使用MDS编码,XP-Code只需XOR计算,且使用公式推导,实现简单。理论分析及与其他典型RAID6算法的比较表明,XP-Code的校验块计算、丢失数据恢复和小写操作等操作的效率都是最优的。     

基于磁盘异或引擎的RAID-5小写性能优化

SCSI标准中已扩充了新的SCSI命令(XDWRITE，XDREAD，XPWRITE等)，用以实现高效RAID-5写操作。对“小写”操作，传统的方法需要主机或RAID控制器读入原有的校验块，通过异或计算来构造新的校验块。采用这些新的SCSI命令实现“小写”操作，不再需要读入校验块，由磁盘来进行异或运算构造出校验块。利用磁盘的异或引擎，提高了RAID-5的吞吐率，缩短了平均响应时间。     

Architectures and algorithms for on-line failure recovery in redundant disk arrays

The performance of traditional RAID Level 5 arrays is, for many applications, unacceptably poor while one of its constituent disks is non-functional. This paper describes and evaluates mechanisms by which this disk array failure-recovery performance can be improved. The two key issues addressed are thedata layout, the mapping by which data and parity blocks are assigned to physical disk blocks in an array, and thereconstruction algorithm, which is the technique used to recover data that is lost when a component disk fails.The data layout techniques this paper investigates are instantiations of thedeclustered parity organization, a derivative of RAID Level 5 that allows a system to trade some of its data capacity for improved failure-recovery performance. We show that our instantiations of parity declustering improve the failure-mode performance of an array significantly, and that a parity-declustered architecture is preferable to an equivalent-size multiple-group RAID Level 5 organization in environments where failure-recovery performance is important. The presented analyses also include comparisons to a RAID Level 1 (mirrored disks) approach.With respect to reconstruction algorithms, this paper describes and briefly evaluates two alternatives,stripeoriented reconstruction anddisk-oriented reconstruction, and establishes that the latter is preferable as it provides faster reconstruction. The paper then revisits a set of previously-proposed reconstruction optimizations, evaluating their efficacy when used in conjunction with the disk-oriented algorithm. The paper concludes with a section on the reliability versus capacity trade-off that must be addressed when designing large arrays.Portions of this material are drawn from papers at the 5th Conference on Architectural Support for Programming Languages and Operating Systems, 1992, and at the 23rd Symposium on Fault-Tolerant Computing, 1993. The work was supported by the National Science Foundation under grant number ECD-8907068, by the Defense Advanced Research Project Agency monitored by ARPA/CMO under contract MDA972-90-C-0035, and by an IBM Graduate Fellowship.