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Topic Review
Sun-Ni Law
Sun-Ni's Law (or Sun and Ni's Law, also known as memory-bounded speedup), is a memory-bounded speedup model which states that as computing power increases the corresponding increase in problem size is constrained by the system’s memory capacity. In general, as a system grows in computational power, the problems run on the system increase in size. Analogous to Amdahl's law, which says that the problem size remains constant as system sizes grow, and Gustafson's law, which proposes that the problem size should scale but be bound by a fixed amount of time, Sun-Ni's Law states the problem size should scale but be bound by the memory capacity of the system. Sun-Ni's Law was initially proposed by Xian-He Sun and Lionel Ni at the Proceedings of IEEE Supercomputing Conference 1990. With the increasing disparity between CPU speed and memory data access latency, application execution time often depends on the memory speed of the system. As predicted by Sun and Ni, data access has become the premier performance bottleneck for high-end computing. From this fact one can see the intuition behind Sun-Ni's Law, as system resources increase, applications are often bottlenecked by memory speed and bandwidth, thus an application can achieve a larger speedup by utilizing all the memory capacity in the system. Sun-Ni's Law can be applied to different layers of a memory hierarchy system, from L1 cache to main memory. Through its memory-bounded function,W=G(M), it reveals the trade-off between computing and memory in algorithm and system architecture design. All three speedup models, Sun-Ni, Gustafson, and Amdahl, provide a metric to analyze speedup for Parallel computing. Amdahl’s law focuses on the time reduction for a given fixed-size problem. Amdahl’s law states that the sequential portion of the problem (algorithm) limits the total speedup that can be achieved as system resources increase. Gustafson’s law suggests that it is beneficial to build a large-scale parallel system as the speedup can grow linearly with the system size if the problem size is scaled up to maintain a fixed execution time. Yet as memory access latency often becomes the dominant factor in an application’s execution time, applications may not scale up to meet the time bound constraint. Sun-Ni's Law, instead of constraining the problem size by time, constrains the problem by the memory capacity of the system, or in other words bounds based on memory. Sun-Ni's Law is a generalization of Amdahl's Law and Gustafson's Law. When the memory-bounded function G(M)=1, it resolves to Amdahl's law, when the memory-bounded function G(M)=m,the number of processors, it resolves to Gustafson's Law.
  • 555
  • 31 Oct 2022
Topic Review
Raft (Computer Science)
Raft is a consensus algorithm designed as an alternative to the Paxos family of algorithms. It was meant to be more understandable than Paxos by means of separation of logic, but it is also formally proven safe and offers some additional features. Raft offers a generic way to distribute a state machine across a cluster of computing systems, ensuring that each node in the cluster agrees upon the same series of state transitions. It has a number of open-source reference implementations, with full-specification implementations in Go, C++, Java, and Scala. It is named after Reliable, Replicated, Redundant, And Fault-Tolerant. Raft is not a Byzantine fault tolerant algorithm: the nodes trust the elected leader.
  • 406
  • 31 Oct 2022
Topic Review
Microsoft DoubleGuard
DriveSpace (initially known as DoubleSpace) is a disk compression utility supplied with MS-DOS starting from version 6.0 in 1993 and ending in 2000 with the release of Windows Me. The purpose of DriveSpace is to increase the amount of data the user could store on disks by transparently compressing and decompressing data on-the-fly. It is primarily intended for use with hard drives, but use for floppy disks is also supported. This feature was removed in Windows XP and later.
  • 230
  • 31 Oct 2022
Topic Review
Homoscedasticity
In statistics, a sequence (or a vector) of random variables is homoscedastic/ˌhoʊmoʊskəˈdæstɪk/ if all its random variables have the same finite variance. This is also known as homogeneity of variance. The complementary notion is called heteroscedasticity. The spellings homoskedasticity and heteroskedasticity are also frequently used. Assuming a variable is homoscedastic when in reality it is heteroscedastic (/ˌhɛtəroʊskəˈdæstɪk/) results in unbiased but inefficient point estimates and in biased estimates of standard errors, and may result in overestimating the goodness of fit as measured by the Pearson coefficient.
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Topic Review
IBM BLU Acceleration
IBM BLU Acceleration is a collection of technologies from the IBM Research and Development Labs for analytical database workloads. BLU Acceleration integrates a number of different technologies including in-memory processing of columnar data, Actionable Compression (which uses approximate Huffman encoding to compress and pack data tightly), CPU Acceleration (which exploits SIMD technology and provides parallel vector processing), and Data Skipping (which allows data that's of no use to the current active workload to be ignored). The term ‘BLU’ does not stand for anything in particular; however it has an indirect play on IBM's traditional corporate nickname Big Blue. (Ten IBM Research and Development facilities around the world filed more than 25 patents while working on the Blink Ultra project, which has resulted in BLU Acceleration.) BLU Acceleration does not require indexes, aggregates or tuning. BLU Acceleration is integrated in Version 10.5 of IBM DB2 for Linux, Unix and Windows,(DB2 for LUW) and uses the same storage and memory constructs (i.e., storage groups, table spaces, and buffer pools), SQL language interfaces, and administration tools as traditional DB2 for LUW databases. BLU Acceleration is available on both IBM POWER and x86 processor architectures.
  • 425
  • 31 Oct 2022
Topic Review
IBM Spectrum Scale
IBM Spectrum Scale is high-performance clustered file system software developed by IBM. It can be deployed in shared-disk or shared-nothing distributed parallel modes. It is used by many of the world's largest commercial companies, as well as some of the supercomputers on the Top 500 List. For example, it was the filesystem of the ASC Purple Supercomputer which was composed of more than 12,000 processors and had 2 petabytes of total disk storage spanning more than 11,000 disks. Before 2015, Spectrum Scale was known as IBM General Parallel File System (GPFS). Like typical cluster filesystems, Spectrum Scale provides concurrent high-speed file access to applications executing on multiple nodes of clusters. It can be used with AIX 5L clusters, Linux clusters, on Microsoft Windows Server, or a heterogeneous cluster of AIX, Linux and Windows nodes. In addition to providing filesystem storage capabilities, Spectrum Scale provides tools for management and administration of the Spectrum Scale cluster and allows for shared access to file systems from remote Spectrum Scale clusters. Spectrum Scale has been available on IBM's AIX since 1998, on Linux since 2001, and on Windows Server since 2008.
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  • 31 Oct 2022
Topic Review
Splinternet
The splinternet (also referred to as cyber-balkanization or internet balkanization) is a characterization of the Internet as splintering and dividing due to various factors, such as technology, commerce, politics, nationalism, religion, and divergent national interests. "Powerful forces are threatening to balkanise it", writes the Economist weekly, and it may soon splinter along geographic and commercial boundaries. The Chinese government erected the "Great Firewall" for political reasons, and Russia has enacted the Sovereign Internet Law that allows it to partition itself from the rest of the Internet, while other nations, such as the US and Australia, discuss plans to create a similar firewall to block child pornography or weapon-making instructions. Clyde Wayne Crews, a researcher at the Cato Institute, first used the term in 2001 to describe his concept of "parallel Internets that would be run as distinct, private, and autonomous universes." Crews used the term in a positive sense, but more recent writers, like Scott Malcomson, a fellow in New America's International Security program, use the term pejoratively to describe a growing threat to the internet's status as a globe-spanning network of networks.
  • 548
  • 31 Oct 2022
Topic Review
Technologies for Improving Storage Efficiency in Blockchain-Based IIoT
The Internet of Things (IoT) and blockchain have contributed to massive advancements in the fields to which they have been applied. The benefits of the blockchain, which include enhanced security, transparency, and greater traceability, make it a promising technology for integration with IIoT, which has long had issues with security. However, there are several issues that limit the integration of blockchain into Industrial Internet of Things (IIoT) systems. One of these issues is the huge storage requirement of the blockchain. There are several solutions to address these concerns. These solutions, which include summarization-based, compression-based, and storage scheme optimization methods, are necessary to enable the further development of blockchain–IIoT integration. However, these solutions have shortcomings that reduce their effectiveness. Compression-based schemes produce compressed blocks or data that accumulate over time and may not ensure enough storage savings on peers. This can be alleviated by designing compression techniques that provide an efficient representation of data for IIoT systems to yield better compression ratios. Summarization-based schemes reduce redundancy in block data by using the net change in transferring entities between parties and, thus, are better suited for financial systems than for IIoT systems. 
  • 728
  • 30 Oct 2022
Topic Review
Iperius Backup
Iperius Backup is a backup software for Windows PCs and Servers, databases and virtual machines. It allows to make automatic backups of files and folders on many devices: external USB hard drives, RDX drives, NAS, LTO tape drives, networked computers, Cloud storage, Amazon S3, Google Drive and FTP servers. Iperius Backup includes drive imaging capabilities, backup of SQL Server, MySQL, PostgreSQL, Oracle databases, backup of Microsoft Exchange servers, backup and replication of VMware ESXi, vCenter, ESXi Free and Hyper-V virtual machines.
  • 1.6K
  • 30 Oct 2022
Topic Review
Java Security
The Java platform provides a number of features designed for improving the security of Java applications. This includes enforcing runtime constraints through the use of the Java Virtual Machine (JVM), a security manager that sandboxes untrusted code from the rest of the operating system, and a suite of security APIs that Java developers can utilise. Despite this, criticism has been directed at the programming language, and Oracle, due to an increase in malicious programs that revealed security vulnerabilities in the JVM, which were subsequently not properly addressed by Oracle in a timely manner.
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