PUBLIC MARKS with tag failover

Takes a look at mod_proxy; mod_jk is very similar.

Failover for hosts

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.

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 high-availability solution works by replicating a disk partition in a master/slave mode. The server that is running as a master has full read/write access to that partition; whereas the server running as slave has absolutely no access to the partition but silently replicates all changes made by the master server.

Pure Load Balancer runs in userland, but relies on an asynchronous non forking/non threaded/non blocking architecture. Thanks to Niels Provos' excellent event library, it can also efficiently use the kernel notification mechanisms to never waste CPU time

You MUST have a third server as a managment node but this can be shut down after the cluster starts. Also note that I do not recommend shutting down the managment server (see the extra notes at the bottom of this document for more information). You can no

In this first of five articles, learn what it means for software to be highly available and how to install and set up heartbeat software from the High-Availability Linux project on a two-node system. You'll also learn how to configure the Apache Web serve

You may know about the MySQL Cluster, which is a complex architecture to achieve high availability and performance. One of the advantages of MySQL Cluster is that each node is a peer to the others, whereas in a normal replicating system you have a master

The Linux Virtual Server is a highly scalable and highly available server built on a cluster of real servers, with the load balancer running on the Linux operating system. The architecture of the server cluster is fully transparent to end users, and the u

Fast Replication With Low Network Demand LifeKeeper Data Replication replicates data at the block level, below the file system. Most importantly, LifeKeeper Data Replication only replicates changes in data and thereby minimizes the demand on systems and n

A LAMP cluster is not the Beowulf kind of cluster that uses specialized message-passing software to tackle a computation-intensive task. It does not cover high availability features, such as automatic failover. Rather, it is a load-sharing cluster that di

One way to overcome the limits of the monolithic server is to distribute the load across many machines. By adding a second (or third) server to the available pool of machines, you can not only increase performance but also add to the stability of the netw

Edit /etc/syslog.conf to include a local1 (for example) facility entry for MasterMySQL to write to. Also update the top line so that local1 doesn't write to /var/log/messages: *.info;local1.none;mail.none;authpriv.none;cron.none /var/log/messa

Replication FAQ. Q: How do I configure a slave if the master is running and I do not want to stop it? A: There are several possibilities. If you have taken a snapshot backup of the master at some point and recorded the binary log filename and offset (fr

Ultra Monkey is a project to create load balanced and highly available network services. For example a cluster of web servers that appear as a single web server to end-users. The service may be for end-users across the world connected via the internet, or