PUBLIC MARKS with tags network & cluster

This guide is the first of a series in which I give you detailed step-by-step instructions on how to build a virtual cluster with Xen. The cluster thus built might not be appropriate for your case, and does reflect the author's preferences and/or needs, but if you are new to clusters or Xen, it will hopefully help you get started with both. The goal is to start it simple and then add more complexity as we progress, so in this first guide I show you how to get do the basics: * A Xen installation, the creation of 5 virtual machines (one to act as the master and four slaves), * Shared storage through NFS, * The network configuration on which to build the virtual cluster. The network structure of this first attempt will be very simple, the master having two network cards, one to the outside world and the other one connected through a switch to the slaves.

Setting Up An iSCSI Environment On Linux Nowadays, the iSCSI technology is quite popular in the storage world. This article shows an iSCSI demo environment which consists of one Debian Linux host and one Netapp Filer.We try to show the most important features of this protocol. 1. What is iSCSI? It is a network storage protocol above TCP/IP. This protocol encapsulates SCSI data into TCP packets. iSCSI allows us to connect a host to a storage array via a simple Ethernet connection (tape drive). This solution is cheaper than the Fibre Channel SAN (Fibre channel HBAs and switches are expensive). From the host view the user sees the storage array LUNs like a local disks. iSCSI devices should not be confused with the NAS devices (for example NFS). The most important difference is that NFS volumes can be accessed by multiple hosts, but one iSCSI volume can by accessed by one host. It is similar to SCSIi protocol: usually only one host has access to one SCSI disk (the difference is the cluster enviroment). The iSCSI protocol is defined in the RFC3720 document by the IETF (Internet Engineering Task Force).

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.

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).