Locally Minimum Storage Regenerating Codes in Distributed Cloud Storage Systems

In distributed cloud storage systems, inevitably there exist multiple node failures at the same time. The existing methods of regenerating codes, including minimum storage regenerating(MSR) codes and minimum bandwidth regenerating(MBR) codes, are mainly to repair one single or several failed nodes, unable to meet the repair need of distributed cloud storage systems. In this paper, we present locally minimum storage regenerating(LMSR) codes to recover multiple failed nodes at the same time. Specifically, the nodes in distributed cloud storage systems are divided into multiple local groups, and in each local group(4, 2) or(5, 3) MSR codes are constructed. Moreover, the grouping method of storage nodes and the repairing process of failed nodes in local groups are studied. Theoretical analysis shows that LMSR codes can achieve the same storage overhead as MSR codes. Furthermore, we verify by means of simulation that, compared with MSR codes, LMSR codes can reduce the repair bandwidth and disk I/O overhead effectively.

DESIGN OF EXACT REGENERATING HIERARCHICAL CODE FOR DISTRIBUTED STORAGE SYSTEM

Erasure code is widely used as the redundancy scheme in distributed storage system. When a storage node fails, the repair process often requires to transfer a large amount of data. Regenerating code and hierarchical code are two classes of codes proposed to reduce the repair bandwidth cost. Regenerating codes reduce the amount of data transferred by each helping node, while hierarchical codes reduce the number of nodes participating in the repair process. In this paper, we propose a "sub-code nesting framework" to combine them together. The resulting regenerating hierarchical code has low repair degree as hierarchical code and lower repair cost than hierarchical code. Our code can achieve exact regeneration of the failed node, and has the additional property of low updating complexity.

Spatiotemporal microRNA profile in peripheral nerve regeneration:miR-138 targets vimentin and inhibits Schwann cell migration and proliferation

While the peripheral nervous system has regenerative ability,restoration of sufficient function remains a challenge.Vimentin has been shown to be localized in axonal growth fronts and associated with nerve regeneration,including myelination,neuroplasticity,kinase signaling in nerve axoplasm,and cell migration;however,the mechanisms regulating its expression within Schwann cell（SC） remain unexplored.The aim of this study was to profile the spatial and temporal expression profile of micro RNA（mi RNA） in a regenerating rat sciatic nerve after transection,and explore the potential role of mi R-138-5 p targeting vimentin in SC proliferation and migration.A rat sciatic nerve transection model,utilizing a polyethylene nerve guide,was used to investigate mi RNA expression at 7,14,30,60,and 90 days during nerve regeneration.Relative levels of mi RNA expression were determined using microarray analysis and subsequently validated with quantitative real-time polymerase chain reaction.In vitro assays were conducted with cultured Schwann cells transfected with mi RNA mimics and assessed for migratory and proliferative potential.The top seven dysregulated mi RNAs reported in this study have been implicated in cell migration elsewhere,and GO and KEGG analyses predicted activities essential to wound healing.Transfection of one of these,mi RNA-138-5 p,into SCs reduced cell migration and proliferation.mi R-138-5 p has been shown to directly target vimentin in cancer cells,and the luciferase assay performed here in rat Schwann cells confirmed it.These results detail a role of mi R-138-5 p in rat peripheral nerve regeneration and expand on reports of it as an important regulator in the peripheral nervous system.

带宽异构网络下的精确修复再生码数据修复方案

再生码技术以高容错性、低冗余开销等优点在数据存储领域得到了广泛应用,但基于再生码的冗余技术在修复失效数据时需从其他帮助节点下载多个编码块。考虑到节点间链路带宽的异构性,在实际网络中链路可用带宽容量变化很大,网络流量最小化并不一定意味着数据修复时间最小化,并且现有针对带宽异构网络下的再生码数据修复方案难以支持精确地修复再生码。由于精确修复再生码具有特定的数学结构,其并行修复难以实现,因此提出一个在带宽异构网络下实现精确修复再生码的数据修复方案ERC-TREE,此方案通过构建一棵最优树来有效利用帮助节点之间的可用带宽,从而实现失效节点数据的精确修复。仿真实验结果表明,在带宽异构网络下采用树型结构修复对精确修复再生码具有可行性。在带宽差异很大的情况下,ERC-TREE的数据修复时间相比星型结构的修复时间减少78%。

长链非编码RNA与牙周炎

背景:近年来,大量研究显示长链非编码RNA(long non-coding RNA,lnc RNA)在牙周炎的发病过程有重要作用,包括免疫反应过程及细胞(牙周膜干细胞、破骨细胞)的生物活性和功能,人们试图通过调控lnc RNA表达水平来实现对牙周炎症的调控及牙周组织的再生。目的:就lnc RNA在牙周炎中的研究进展进行综述,以期望更好地推进lnc RNA在牙周炎的研究。方法:第一作者检索Pub Med、中国知网等数据库建库到2023年3月发表的相关文献,以“长链非编码RNA,lnc RNA,牙周炎,牙周,免疫,炎症,牙周膜干细胞,破骨细胞,成骨分化,骨吸收,骨形成,复发,缺氧,氧化应激,静态机械应变”为中文检索词;“lnc RNA,periodontitis,periodontal,immunity,inflammation,periodontalmembranestemcells,osteoclasts,osteogenicdifferentiation,bone resorption,bone formation,recurrence,hypoxia,oxidative stress,static mechanical strain”为英文检索词,阅读每篇文献的文题、摘要进行初筛,最终筛选出87篇文献进行归纳分析。结果与结论:(1)牙周致病菌刺激机体导致免疫效应失衡引发炎症反应造成牙周组织的破坏,lnc RNA参与其调控机制。(2)lnc RNA对炎性环境的牙周膜细胞主要参与了促炎的调控,对于破骨细胞分化的影响,通过ce RNA机制进行调控,为探究牙周炎发病机制提供了新的线索。对于B细胞及巨噬细胞,lnc RNA在牙周炎中可调控其亚群的浸润、细胞活性和功能发挥。(3)lnc RNA参与牙周炎相关免疫反应主要在Toll样受体与NOD样受体两种模式识别受体与核因子κB途径这一信号通路发挥作用。(4)探究lnc RNA是否可作为牙周炎生物学标志在牙周炎的诊断及预后复发问题上有很大价值。(5)已有动物实验证实了可以通过调控lnc RNA的表达水平来逆转lnc RNA在牙周炎的作用从而起到抗炎作用,其对牙周炎的免疫治疗研究有很大价值。(6)Lnc RNA对于牙周膜干细胞的调控主要通过内源性竞争机制及各种信号通路实现,且其作用受多种因素影响,如炎性环境、机械应变及缺氧和氧化应激等,通过这些相关因素进行相关机制的研究为牙周炎的治疗提供了新的思路。

S-E-MBR:一种基于E-MBR码的分布式存储系统扩容方法

随着数据量的激增,以再生码为容错机制的分布式存储系统需要使用扩容技术扩充其存储容量。然而现有再生码扩容方法较少,在扩容时间与传输量方面有待提高。为此,针对在线分布式存储场景提出一种扩容方法 S-EMBR,以更高效的迁移方式降低迁移的数据块数量和I/O开销,减少校验更新时所需数据块,使其达到了理论数据块迁移量最优值。理论分析与实验结果表明,与RR与Scale-RS方法相比,S-E-MBR方法扩容时的数据传输量分别减少了52.7%~77.9%和41.3%~50.4%,扩容总时间分别减少了72.3%~75.4%和50.6%~53.5%,响应速度分别提升了39.2%和17.1%,可满足在线扩容场景需求。

一类精确修复多个错误的Suh-Ramchandran码

再生码因能有效地减少修复带宽,更适用于分布式存储系统。利用干扰对齐技术,对于任意的参数(n,k,d),满足n≥2k且d≥2k-1。Suh和Ramchandran构造了修复一个失效节点时,可达到最优修复带宽的最小存储再生码。基于Suh-Ramchandran再生码,重新描述了参数(n=2k+1;k)下的编码结构,并说明这种码为一类可修复多个失效节点的再生码,且在修复单个或多个失效节点时均可达到最优的修复带宽。

周围神经损伤后再生的表观遗传学调控机制研究进展

周围神经损伤反应及影响再生的表观遗传学机制尚未被阐明。本文着眼于表观遗传学调控机制,从DNA甲基化、组蛋白修饰、非编码RNA等方面对周围神经损伤后再生的表观遗传学调控机制进行综述,为优化周围神经损伤后再生的临床治疗提供基础知识。

废航空润滑油再生工艺研究

以废航空润滑油(UO)为原料,采用蒸馏-加氢-吸附精制工艺制备了再生基础油。通过GC-MS、1H NMR、FTIR等分析手段对UO、加氢精制油(HO)的组分特征进行了表征。对原料和产品的色度和黏度指数进行了测定。结果表明,选取<370℃的UO馏分经过加氢精制后,HO的黏度指数为122,饱和烃质量分数为92.26%,色度为2.5,仅通过单独加氢处理工艺得到的再生基础油的色度不符合标准,采用10%的活性白土,在140℃搅拌1.5 h对HO进一步脱色,得到的再生基础油黏度指数为125,饱和烃含量为95%,色度为0.3,符合VHVI5号的再生基础油标准。加氢精制油中的着色物质主要是酮、醛类化合物。

AVirtual Cloud Storage Architecture for Enhanced Data Security

The sensitive data stored in the public cloud by privileged users,such as corporate companies and government agencies are highly vulnerable in the hands of cloud providers and hackers.The proposed Virtual Cloud Storage Archi-tecture is primarily concerned with data integrity and confidentiality,as well as availability.To provide confidentiality and availability,thefile to be stored in cloud storage should be encrypted using an auto-generated key and then encoded into distinct chunks.Hashing the encoded chunks ensured thefile integrity,and a newly proposed Circular Shift Chunk Allocation technique was used to determine the order of chunk storage.Thefile could be retrieved by performing the opera-tions in reverse.Using the regenerating code,the model could regenerate the missing and corrupted chunks from the cloud.The proposed architecture adds an extra layer of security while maintaining a reasonable response time and sto-rage capacity.Experimental results analysis show that the proposed model has been tested with storage space and response time for storage and retrieval.The VCSA model consumes 1.5x(150%)storage space.It was found that total storage required for the VCSA model is very low when compared with 2x Replication and completely satisfies the CIA model.The response time VCSA model was tested with different sizedfiles starting from 2 to 16 MB.The response time for storing and retrieving a 2 MBfile is 4.96 and 3.77 s respectively,and for a 16 MBfile,the response times are 11.06 s for storage and 5.6 s for retrieval.

CRL： Efficient Concurrent Regeneration Codes with Local Reconstruction in Geo-Distributed Storage Systems

As a typical erasure coding choice, Reed-Solomon （RS） codes have such high repair cost that there is a penaltyfor high reliability and storage efficiency, thereby they are not suitable in geo-distributed storage systems. We present anovel family of concurrent regeneration codes with local reconstruction （CRL） in this paper. The CRL codes enjoy threebenefits. Firstly, they are able to minimize the network bandwidth for node repair. Secondly, they can reduce the numberof accessed nodes by calculating parities from a subset of data chunks and using an implied parity chunk. Thirdly, they arefaster than existing erasure codes for reconstruction in geo-distributed storage systems. In addition, we demonstrate howthe CRL codes overcome the limitations of the Reed-Solomon codes. We also illustrate analytically that they are excellent inthe trade-off between chunk locality and minimum distance. Furthermore, we present theoretical analysis including latencyanalysis and reliability analysis for the CRL codes. By using quantity comparisons, we prove that CRL（6, 2, 2） is only0.657x of Azure LRC（6, 2, 2）, where there are six data chunks, two global parities, and two local parities, and CRL（10,4, 2） is only 0.656x of HDFS-Xorbas（10, 4, 2）, where there are 10 data chunks, four local parities, and two global paritiesrespectively, in terms of data reconstruction times. Our experimental results show the performance of CRL by conductingperformance evaluations in both two kinds of environments： 1） it is at least 57.25% and 66.85% more than its competitorsin terms of encoding and decoding throughputs in memory, and 2） it has at least 1.46x and 1.21x higher encoding anddecoding throughputs than its competitors in JBOD （Just a Bunch Of Disks）. We also illustrate that CRL is 28.79% and30.19% more than LRC on encoding and decoding throughputs in a geo-distributed environment.

分布式存储系统中基于Pyramid码的局部性修复编码

为了提高分布式存储系统的存储可靠性以及故障节点的修复效率,提出一种基于Pyramid码的局部性修复编码方案。该编码方案采用Pyramid码的最小可实现编码结构,划分局部修复组,确保较低的修复局部性并实现故障节点的快速修复。性能分析表明,基于Pyramid码的局部性修复编码可实现存储系统中多个故障节点的快速修复,具有较低的修复局部性,且相对于三副本复制策略以及简单再生码,基于Pyramid码的局部性修复编码在存储开销和修复带宽开销方面的性能更优。

基于再生码的拟态数据存储方案

针对云存储系统由于静态的存储架构和存储模式而带来的安全威胁,提出一种基于再生码的拟态化存储方案。该方案利用网络编码方案将数据存储在云端数据节点上,采用一种基于再生码的拟态变换机制,可根据随机时变因素动态地改变数据的存储状态,且能够保证数据完整性和数据持续可用性。拟态变换机制具有随机性、时变性和动态性,通过增加存储系统的不确定性,可阻断和干扰攻击链,增加了攻击者实施攻击的难度和成本,提高了系统的安全性和可靠性。

用于云存储的安全容错编码

针对当前基于RC编码的容错技术的安全缺陷,提出了一种安全编码——SRCS编码,以保证在云计算以及云存储这种高度开放环境下,存储系统容错过程中数据的安全性。该编码将门限体制引入到了传统的RC编码当中,利用基于公钥的门限体制保护编码矩阵,在确保基于传统RC编码的容错技术高效、低冗余优势的前提下,解决了其在开放环境下编码矩阵存在的安全问题。最后利用判定性BDHE假设,在部分适应性攻击模型下证明了SRCS编码的安全性。

大数据存储中的容错关键技术综述

不断增长的海量数据需要被可靠存储,而分布式存储系统庞大的节点规模和数据规模,大大提升了发生节点失效的概率,容错技术成为大数据存储中不可忽视的关键技术。文中介绍了数据容错的两种基本策略:复制和纠删码,并分别总结了将这两种容错策略具体应用于大数据存储时所面对的问题和相关解决技术,如与基于复制的容错技术相关的副本系数设置、副本放置策略、副本一致性策略、副本修复策略和纠删码领域的再生码技术等。

分布式存储系统最小带宽再生码研究

分布式存储系统常常使用纠删码冗余技术提高系统可靠性.为保证一定的冗余度,系统必须具有自修复能力再生失效数据.再生码是纠删码的一种改进形式,最大特点在于无需下载整个数据文件就能恢复单个节点数据,从而有效减少数据修复时的网络带宽.相关文献证明再生码数据修复时存在极值点—最小带宽再生点(MBR),由此提出最小带宽再生码MBRC.文中从数据分布、失效数据修复和数据重构三个方面描述了实现的原理,并通过构建数据矩阵和修复矩阵实现MBRC再生码.利用实例详细给出了再生码的实现过程,并理论证明正确性,最后仿真实验验证了MBRC的有效性.

一种云存储中基于干扰对齐的多节点精确修复方法

本文提出了一种基于干扰对齐的满足MDS性质的多节点精确修复码(MMSR).首先利用柯西矩阵构造MMSR码的生成矩阵,使其适用干扰对齐技术,并同时修复多个节点.然后讨论了MMSR码同步修复和异步修复方案的优缺点.最后证明了MMSR码的MDS性质,并通过一个(7,3,5)-MMSR码的数据重建方案验证了MMSR码的MDS性质和可行性.

基于再生码的云存储系统——Ustor

当前常使用多个云共同存储数据，以保证用户数据可靠性。为减少存储成本和修复带宽，提出了一种使用功能性修复再生码（FRC）将数据编码为多个数据块，并分布于不同的云中的方法。该方法减少了多个云中单个云发生数据丢失时需要从网络上传输的数据量，并减少了修复成本，已成功地应用于所构建的云存储系统Ustor中。实验表明：与不编码比较，冗余编码给系统增加了5%~10%的响应时间开销，但可保障节点失效；FRC码编、解码和修复速度与里德-所罗门（Reed-Solomon或RS）码基本相当，256 MB大小文件编码时间差距在0.5 s以内；FRC码修复时与传统的RS码相比减少了25%以上需要下载的数据量。

适用于再生编码分布式存储的轻量型隐私保护审计方案

为了降低面向再生编码分布式存储系统的外包数据审计机制的安全实现开销,提出了一种正交化代数编码方法,以此构造一类基于线性同态认证的轻量型隐私保护审计方案。利用文件编码数据与私有密钥向量的正交化构造外包存储向量的同态认证标签,并提出利用密钥特定分量的正交基向量组的随机化掩码来完成审计响应消息的隐私保护,实现代数编码、隐私保护和安全审计的高效融合。理论分析表明,所提方案在再生编码分布式存储应用中可实现信息理论意义下的安全性。与现有同类工作相比,该方案计算复杂度低,通信开销小,具有更好的性能优势。

基于精确再生码的秘密共享方案

为解决云存储系统中数据安全性问题,利用精确再生码构造一种新的(t,n)门限秘密共享方案。方案由子秘密的分发、原始秘密的恢复和子秘密丢失者的数据重建共3种算法组成。子秘密的分发就是将原始秘密先进行分块,再进行纠删编码,最后按一定的规则将编码后的数据块分发给n个分享者。选取t个分享者提供的数据块,按纠删码的译码算法恢复原始秘密。选取t个以上分享者的数据块,按精确再生码的译码算法重建出子秘密丢失者的数据。研究结果表明:访方案是一种信息论安全的门限体制,与传统的基于Lagrange多项式插值算法的秘密共享方案相比,具有运算复杂性低、节点存储量小、丢失子秘密易再生等优点。