An Implementation of High Availability in Networked Robotic Systems

A large class of modern distributed file systems treat metadata services as an independent system component, separately from data servers. The availability of the metadata service is key to the availability of the overall system. Given the high rates of failures observed in large-scale data centers, distributed file systems usually incorporate high-availability (HA) features. A typical approach in the development of distributed file systems is to design and develop metadata services from the ground up, at significant cost in terms of complexity and time, often leading to functional shortcomings. Our motivation in this paper was to improve on this state of things by defining a general-purpose architecture for HA metadata services (which we call RMS) that can be easily incorporated and reused in new or existing file systems, reducing development time. Taking two prominent distributed file systems as case studies, PVFS and HDFS, we developed RMS variants that improve on functional shortcomings of the original HA solutions, while being easy to build and test. Our extensive evaluation of the RMS variant of HDFS shows that it does not incur an overall performance or availability penalty compared to the original implementation.

Server is a computer system that provides the kind of service in a computer network. One of the functions of the server is as data storage. Computers servers with high availability values are generally referred to as High Availability (HA) Server. HA enables a server can be operational in a sustainable manner for long periods of time. Now, HA has been combined with a cluster technique known as High Availability Clusters or failover cluster. In this research the author intends to apply, analyze, and implement a network file server that has a high availability of service. Researchers used a pacemaker as cluster resource management, Corosync as cluster messaging service and DRBD for the synchronization of data if a failover occurs and measured network performer cluster file system that does have a high availability service. The result is a network file system or the availability of the cluster has a value of 99.998% availability, which means it has a High Availability. The server network file system failover cluster meets the conditions, which, if the primary server (master) dies it will be replaced by a slave server.

In recent decades, virtualization as an abstraction from physical hardware has become a popular solution to resource isolation and server consolidation. With the surge in adoption of virtualization technologies, ensuring High Availability (HA) for applications hosted in virtualized environments emerges as an important problem and has garnered substantial attention. In this paper, we present a brief comparison of virtualization technologies from a HA perspective. The state-of-the-art HA solutions in two mainstream types of virtualized platforms (i.e., hypervisor-based platform and container-based platform) are respectively investigated in terms of limitations and features such as live migration, failure detection, and checkpoint/ restore. One of our key findings is that, compared with hypervisor-based platforms, HA features in container-based platforms are far from enough. From a HA perspective, extensions on top of container technologies are required.

In our increasingly wired world, there is a stringent need for the IT community to provide uninterrupted services of networks, servers and databases. Considerable efforts, both by the industrial and academic community have been directed to this end. In this paper, we examine the requirements for high availability, measures used to express it, and approaches used to implement this for databases. We present a high availability solution, using off the shelf hardware and software components, for transactions based applications and give our experience with this system.

In this paper, we propose a new paradigm for network file system design, serverless network file systems. While traditional network file systems rely on a central server machine, a serverless system utilizes workstations cooperating as peers to provide all file system services. Any machine in the system can store, cache, or control any block of data. Our approach uses this location independence, in combination with fast local area networks, to provide better performance and scalability than traditional file systems. Further, because any machine in the system can assume the responsibilities of a failed component, our serverless design also provides high availability via redundant data storage. To demonstrate our approach, we have implemented a prototype serverless network file system called xFS. Preliminary performance measurements suggest that our architecture achieves its goal of scalability. For instance, in a 32-node xFS system with 32 active clients, each client receives nearly as much read or write throughput as it would see if it were the only active client.

In the last chapter, we talked about some basic things about MVCC in PostgreSQL, and what is bloat in the database and how it can be removed. We explained how autovacuum helps in removing bloat and improving performance. We also covered the best practices to execute maintenance activities like vacuum, reindex in detail. In this chapter, we will talk about the importance of High Availability (HA), and what information we need to build an HA solution and the procedures to implement it in PostgreSQL. We will cover some open source and enterprise tools to implement HA. We will also cover the importance of a pooler, and available poolers on the market and their implementation.

This paper describes a simple distributed mechanism for caching files among a networked collection of workstations. We have implemented it as part of Sprite, a new operating system being implemented at the University of California at Berkeley. A preliminary version of Sprite is currently running on Sun-2 and Sun-3 workstations, which have about 1-2 MIPS processing power and 4-16 Mbytes of main memory. The system is targeted for workstations like these and newer models likely to become available in the near future; we expect the future machines to have at least five to ten times the processing power and main memory of our current machines, as well as small degrees of multiprocessing. We hope that Sprite will be suitable for networks of up to a few hundred of these workstations. Because of economic and environmental factors, most workstations will not have local disks; instead, large fast disks will be concentrated on a few server machines.

As an important IT infrastructure, website is a system which requires high reliability and availability levels. Website meets the criteria as a highly available system because website must provide services to clients in real time, handle a large amount of data, and not lose data during transaction . A highly available system must meet the condition of being able to run continuously as well as guaranteeing consistency on data requests. This study designed a website with high availability. The approach was building network cluster with failover and replicated block device functions . Failover was built to provide service availability, while replicated block device provides data consistency during failure of service . With failover cluster and replicated block device approaches, a cluster which is able to handle service failures of web server and database server on the website. The result of this study was the services of the website could run well if there was any failure in node members of the cluster. The system was able to provide 99,999 (five nines) availability on database server services and 99,98 (three nines) on web server services .

Peer-to-peer (P2P) systems are, in contrast to client-server (C/S) systems, fault-tolerant, robust, and scalable. While C/S distributed file systems, such as NFS (network file system) or SMB (server message block), do not scale with respect to the number of clients and exhibit a single point of failure, P2P file systems have the potential to cope with an increasing number of participants. Thus, this paper presents DRFS (distributed reliable file system), a P2P file system for cooperative environments. DRFS uses random, content-independent identifiers for data storage, while maintaining high performance and low overhead with many concurrent reads and writes. A dynamic replication mechanism ensures data availability, even under high churn. The application scenario considers an office environment, where DRFS is installed on employees' machines, who store and request files. DRFS has been implemented using the Filesystem in Userspace (FUSE) interface, in order to provide users with transparent read and write operations. Experiments show the benefits of such a peer-to-peer architecture, when a small number of peers reads or writes in parallel: DRFS performs better than NFS, as soon as 6 peers read or write in parallel a 32 MB file. For unpopular files, it is also more reliable than IgorFS.

인터넷 환경의 급속한 발전과 더불어 국내외 미션 크리티컬한 비즈니스 환경이 온라인에 의해 서비스 되고 있다. 따라서 웹 환경을 통해 처리되어야 할 정보의 양의 급증과, 이의 처리를 위해 여러 개의 단일 서버를 고속의 네트워크로 연결한 고가용성 구현이 가능한 클러스터 컴퓨팅 시스템이 등장하게 되었다. 그 결과 클러스터 기반 DBMS에 관한 연구와 상용화된 솔루션을 통해 국내외적으로 활발히 진행 중이며, 이에 따라 클러스터 기반 DBMS를 효율적이고 최적화된 상태의 관리 연구는 미흡한 실정이다. 따라서 본 논문에서는 클러스터 기반 DBMS를 위한 고가용성 클러스터 솔루션의 최적화된 관리 기법과 이론에 대해 알아본다. In these days, Internet environment are very quickly development as well On-line service have been using a online for the mission critical business around the world. As the amount of information to be processed by computers has recently been increased there has been cluster computing systems developed by connecting workstations server using high speed networks for high availability. As a result, this study on a cluster based DBMS and common solution of DBMS venders has been studying with a wide range, as well as It is not good study a management skill for the cluster-based DBMS efficiently and optimization. accordingly, This study find out optimization managements skill and theory of he High availability solution on cluster-based DBMS.

Broadband Power Line Communications (BPL) is a technology that has proved to be a very suitable option for the deployment of Smart Grid solutions. It provides a low cost, proprietary, high performance future-proof backhaul between Secondary Substations. This paper will focus on the description of the different "Fault Cases" that might occur in medium voltage BPL communication architecture and their consequent High Availability solution, taking advantage of Iberdrola's experience in the use and maintenance of this technology along its large scale Smart Grid deployment. The description of the High Availability functionality and the results of the tests developed so far are presented in this paper so that utilities might find it useful to provide an added value in their own Smart Grid deployments.

Users rarely consider running network file systems over slow or wide-area networks, as the performance would be unacceptable and the bandwidth consumption too high. Nonetheless, efficient remote file access would often be desirable over such networks---particularly when high latency makes remote login sessions unresponsive. Rather than run interactive programs such as editors remotely, users could run the programs locally and manipulate remote files through the file system. To do so, however, would require a network file system that consumes less bandwidth than most current file systems.This paper presents LBFS, a network file system designed for low-bandwidth networks. LBFS exploits similarities between files or versions of the same file to save bandwidth. It avoids sending data over the network when the same data can already be found in the server's file system or the client's cache. Using this technique in conjunction with conventional compression and caching, LBFS consumes over an order of magnitude less bandwidth than traditional network file systems on common workloads.

This paper presents Kosha, a peer-to-peer (p2p) enhancement for the widely-used Network File System (NFS). Kosha harvests redundant storage space on cluster nodes and user desktops to provide a reliable, shared file system that acts as a large storage with normal NFS semantics. P2p storage systems provide location transparency, mobility transparency, load balancing, and file replication - features that are not available in NFS. On the other hand, NFS provides hierarchical file organization, directory listings, and file permissions, which are missing from p2p storage systems. By blending the strengths of NFS and p2p storage systems, Kosha provides a low overhead storage solution. Our experiments show that compared to unmodified NFS, Kosha introduces a 4.1% fixed overhead and 1.5% additional overhead as nodes are increased from one to eight. For larger number of nodes, the additional overhead increases slowly. Kosha achieves load balancing in distributed directories, and guarantees 99.99% or better file availability.

Cloud computing provides virtual resources so that end-users or organizations can buy computing power as a public utility. Cloud service providers however must strive to ensure good QoS by offering highly available services with dynamically scalable resources. HA-OSCAR is an open source High Availability (HA) solution for HPC/cloud that offers component redundancy, failure detection, and automatic fail-over. In this paper, we describe HA-OSCAR as a cloud platform and analyze system availability of two potential cloud computing systems, OSCAR-V cluster and HA-OSCAR-V. We also explore our case study to improve Nimbus, a popular cloud IaaS toolkit. The results show that the system that deploys HA-OSCAR has a significantly higher degree of availability.

It is important for any organization to handle increase in data; normally this is the job of the DBA in organization to take care of this data growth, along with its protection and its availability. High availability of data is also most important for organizations, for that purpose, shared storage is usually the solution, for example, SAN or NAS storage as Microsoft Cluster Database instances. Mostly Organization does not have shared storage in their infrastructure, which was required for Microsoft cluster SQL database instance; due to that they used other native methods to implement like log shipping or database mirroring, which was not efficient method for high-availability and disaster-recovery solution. After that, Microsoft introduced native method called SQL AlwaysOn method that could be implemented without using SAN and NAS storage method to implement high availability and disaster recovery without using shared storage. SQL AlwaysOn option is using only Microsoft cluster service and shared folder between the nodes. This paper written for DBA and System Administrators; and is implementation of Microsoft SQL Database tier step by step.