PUBLIC MARKS from holyver with tag cluster

L’infrastructure utilisée par le géant de la recherche Google est un mystère que beaucoup aimeraient percer, que ce soit les concurrents ou les utilisateurs étonnés de la réactivité sans faille des services malgré un nombre d’utilisateurs record.

Google is the King of scalability. Everyone knows Google for their large, sophisticated, and fast searching, but they don't just shine in search. Their platform approach to building scalable applications allows them to roll out internet scale applications at an alarmingly high competition crushing rate. Their goal is always to build a higher performing higher scaling infrastructure to support their products. How do they do that?

ClusterSSH controls a number of xterm windows via a single graphical console window to allow commands to be interactively run on multiple servers over an ssh connection.

Lors de la mise en production d'une application Internet ou intranet, il est fréquent de vouloir protéger les transferts par une connexion sécurisée (HTTPS). Même si Tomcat le permet (il suffit d'activer une option dans le server.xml de Tomcat), utiliser Apache est un meilleur choix du fait de sa vitesse. De plus l'utilisation d'Apache permet de se débarrasser des :8080 et autres numéros de ports dans l'url, du fameux " /MonApp " à la fin de la dite url et enfin la possibilité il offre une intégration plus aisée dans un environnement avec charge répartie (Load Balancing).

Clustering Clustering support was added in Jackrabbit 1.2.1. This works as follows: content is shared through all cluster nodes. Every change made by one cluster node is reported in a journal, which can be either file based or written to some database. Prerequisites In order to cluster some repository nodes, the following prerequisites must be met: * The persistence managers must store their data in the same, globally accessible location * Every cluster node must be assigned a unique ID * A journal type must be chosen, either based on files or stored in a database

Ce document étudie les infrastructures et les différents types et méthodes de haute disponibilité dans un environnement donné. Il présente aussi les différentes solutions en termes logiciels et matériels afin de parvenir à une haute disponibilité. Ce document est une documentation ouverte.

MySQL provides a built-in data replication functionality for maintaining identical copies of its data to one or more backend servers, thus providing a simple High Availability mechanism. On the other hand, the Open Source community has several projects to implement failover techniques, being one of them Heartbeat. This article will show you how to implement a clustered, highly available and inexpensive solution based on GNU/Linux and combining MySQL as the database engine and Heartbeat as the failover mechanism. The configuration will consist of a 2-node active/passive cluster.

# 1 Présentation de VMware Virtual Infrastructure 3 * 1.1 ESX Server 3 * 1.2 VMware Virtual Center 2 * 1.3 Consolidated Backup # 2 Infrastructure requise * 2.1 Schéma général d'un infrastructure complète * 2.2 Réseaux * 2.2 SAN * 2.3 Sauvegardes # 3 Installation des serveurs physiques * 3.1 VMware ESX 3 * 3.2 Virtual Center * 3.3 Consolidated Backup # 4 Démonstration des fonctionnalités offertes * 4.1 Sécurisation des données * 4.2 VMotion * 4.3 VMware DRS * 4.4 VMware HA # Conclusion

Enterprise application (EA) architects often face challenges in designing scalable applications that can accommodate a growing number of users and provide 24/7 availability. In this article, I’ll explain the meaning of scalability and availability in EA and explore different architectures for achieving them.

This following sections describe alternative architectures for a WebLogic Server cluster: * Architectural and Cluster Terminology * Recommended Basic Architecture * Recommended Multi-Tier Architecture * Recommended Proxy Architectures * Security Options for Cluster Architectures

Les EJB sont particulièrement nécessaires pour des applications critiques sur de grosses architectures matérielles, là où les ressources ne sont qu’un problème secondaire et où les avantages des EJB (gestion déclarative des transactions, distribution d’objets et support de la persistence automatique) prennent tout leur sens. Dans ce type de contexte, la tolérance aux pannes et la répartition de la charge sont des élements vitaux. Le clustering est la technologie permettant de répondre à ces 2 préoccupations. Ce document va donc s’intéresser à la bonne façon de le mettre en oeuvre en tentant de mettre en avant les pièges inhérents à l’utilisation d’un cluster.

DRBD is a block device which is designed to build high availability clusters. This is done by mirroring a whole block device via (a dedicated) network. You could see it as a network raid-1.

A l"heure où les serveurs d"entreprises doivent stocker un volume croissant de données et assurer une haute disponibilité, il est nécessaire d"imaginer des systèmes de mirroring (miroir) autres que simplement sur des disques durs. La redondance de disques durs (RAID-1, RAID-5) permet déjà d"avoir une bonne résistance aux pannes d"un disque (ou plusieurs si on est en RAID-5). Cependant, si c"est la machine qui tombe (le processeur, l"alimentation, le contrôleur de disque,...), on n"a aucun moyen pour relancer le tout rapidement sans perte de données. Ayant été confronté à cette problématique, j"ai envisagé une solution de RAID-1 au travers du réseau. C"est-à-dire que sur deux serveurs, on a deux partitions (une par serveur) qui sont à tout moment une copie exacte l"une de l"autre. C"est un mirroring (miroir) de partitions à travers une interface réseau.

L"idée générale pour assurer la disponibilité d"un service est de faire fonctionner plusieurs machines (deux au minimum) en même temps. Ces machines forment ce qu"on appelle un cluster et chaque machine est un node du cluster. Chacune des machines va vérifier si les autres répondent toujours en prenant le pouls de chacune des autres. Si une machine cesse de fonctionner, les autres assurent le service. Une fois le cluster configuré, on y accède au travers d"une seule et unique adresse IP qui est celle du cluster; qui lui-même est composé de plusieurs nodes. Pour pouvoir mettre en place ce genre de technique, nous allons utiliser l"application HeartBeat qui va se charger de surveiller les machines et d"appliquer une série de scripts définis par l"utilisateur si cela s"avère nécessaire (c"est-à-dire si une machine tombe).

This is only ONE way to keeps nodes in synchronization for a high availability cluster. It suits our needs and may be a good starting block for others so I'm sharing it. Your mileage may vary. We used this on a web server to update ~1GB worth of documents in sync every 10 minutes. Depending on how quickly your files change, you may be able to update more data, more frequently. I would not recommend using this without a private fast ethernet channel, i.e. an extra NIC in each node connected via a crossover cable.

This tutorial shows how to configure a MySQL 5 cluster with three nodes: two storage nodes and one management node. This cluster is load-balanced by a high-availability load balancer that in fact has two nodes that use the Ultra Monkey package which provides heartbeat (for checking if the other node is still alive) and ldirectord (to split up the requests to the nodes of the MySQL cluster).

In this tutorial I will describe how to set up a highly available NFS server that can be used as storage solution for other high-availability services like, for example, a cluster of web servers that are being loadbalanced. If you have a web server cluster with two or more nodes that serve the same web site(s), than these nodes must access the same pool of data so that every node serves the same data, no matter if the loadbalancer directs the user to node 1 or node n. This can be achieved with an NFS share on an NFS server that all web server nodes (the NFS clients) can access.

Many IT administrators have discovered that there is overlap between consolidation and virtualization, and they are wondering how they should reconcile these two techniques in datacenter environments. Virtualization tools such as partitions, virtual machines, and resource management software all enable multiple dominant workloads to run simultaneously on larger servers, which is typically a key aspect of consolidation. But virtualization also offers far-reaching opportunities for administrators to fundamentally transform the operations in their datacenters.

Server clusters and server virtualization may be two different animals, but they're animals that can work well together in a data center, says Hakon Bugge, founder and CTO of Scali Inc., a Linux clustering systems provider in Marlborough, Mass.

Web tier clustering is an important part of J2EE scalability and high availability. Traditionally, load balancing is done via front end load balancer (either software- or hardware-based) while the session replication (for fail-over) is done by the web container. Here we have done a benchmark study of http session replication using JBoss Application Server (AS). We also compare JBoss performance against the Tomcat standalone. Please note that JBoss web container also uses embedded Tomcat in non-clustered mode. They differ only in the clustering solution module. For details of both implementation, please refer to both the JBoss and Tomcat documentation. The HttpSession replication performance comparisons are based on JBoss AS 4.0.3SP1 (with JBossCache 1.2.4 and JGroups 2.2.9). Previously, we have published results based on JBoss AS 4.0.2 (August 2005). But the current version has been found to provide dramatic performance improvement.

Clustering allows us to run an applications on several parallel servers (a.k.a cluster nodes). The load is distributed across different servers, and even if any of the servers fails, the application is still accessible via other cluster nodes. Clustering is crucial for scalable enterprise applications, as you can improve performance by simply adding more nodes to the cluster. The JBoss Application Server (AS) comes with clustering support out of the box. The simplest way to start a JBoss server cluster is to start several JBoss instances on the same local network, using the run -c all command for each instance. Those server instances, all started in the all configuration, detect each other and automatically form a cluster. In the first section of this chapter, I discuss basic concepts behind JBoss's clustering services. It is important that you understand those concepts before reading the rest of the chapter. Clustering configurations for specific types of applications are covered after this section.

Lors de la mise en production d'une application Internet ou intranet, il est fréquent de vouloir protéger les transferts par une connexion sécurisée (HTTPS). Même si Tomcat le permet (il suffit d'activer une option dans le server.xml de Tomcat), utiliser Apache est un meilleur choix du fait de sa vitesse. De plus l'utilisation d'Apache permet de se débarrasser des :8080 et autres numéros de ports dans l'url, du fameux " /MonApp " à la fin de la dite url et enfin la possibilité il offre une intégration plus aisée dans un environnement avec charge répartie (Load Balancing).

The latest version of the Tomcat servlet container provides clustering and load balancing capabilities that are essential for deploying scalable and robust web applications. The first part of this article provides an overview of installation, configuration, usage, and extension of clustering and load balancing features. The second will introduce a sample web application to demonstrate the steps involved in configuring Tomcat server instances to enable clustering, and will study session persistence using in-memory replication in the cluster environment.

C-JDBC is a database cluster middleware that allows any Java™ application (standalone application, servlet or EJB™ container, ...) to transparently access a cluster of databases through JDBC™. You do not have to modify client applications, application servers or database server software. You just have to ensure that all database accesses are performed through C-JDBC.

This page discusses cluster- and clustering-related questions. Please make sure to read the Clustering HowTo page in the main Tomcat documentation bundle as well.