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Red Hat ENTERPRISE LINUX 4 Manual

Cluster suite overview
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Red Hat Enterprise Linux 4

Cluster Suite Overview
Red Hat Cluster Suite for Red Hat Enterprise Linux

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  • Page 1: Red Hat Enterprise Linux

    Red Hat Enterprise Linux 4 Cluster Suite Overview Red Hat Cluster Suite for Red Hat Enterprise Linux...
  • Page 2 Cluster Suite Overview Red Hat Enterprise Linux 4 Cluster Suite Overview Red Hat Cluster Suite for Red Hat Enterprise Linux Edition 1.0 Copyright © 2009 Red Hat, Inc. This material may only be distributed subject to the terms and conditions set forth in the Open Publication License, V1.0 or later (the latest version of the OPL is presently available at http://www.opencontent.org/openpub/).

  • Page 3: Table Of Contents

    Introduction 1. Document Conventions ....................vi 1.1. Typographic Conventions ..................vi 1.2. Pull-quote Conventions ..................vii 1.3. Notes and Warnings ................... viii 2. Feedback ........................ix 1. Red Hat Cluster Suite Overview 1.1. Cluster Basics ......................1 1.2. Red Hat Cluster Suite Introduction ................2 1.3.
  • Page 5 Red Hat Cluster Suite documentation and other Red Hat documents are available in HTML, http:// PDF, and RPM versions on the Red Hat Enterprise Linux Documentation CD and online at www.redhat.com/docs/. For more information about Red Hat Cluster Suite for Red Hat Enterprise Linux 4, refer to the following resources: •...

  • Page 6: Document Conventions

    Red Hat Cluster Suite documentation and other Red Hat documents are available in HTML, http:// PDF, and RPM versions on the Red Hat Enterprise Linux Documentation CD and online at www.redhat.com/docs/. 1. Document Conventions This manual uses several conventions to highlight certain words and phrases and draw attention to specific pieces of information.

  • Page 7: Pull-Quote Conventions

    Pull-quote Conventions Choose System > Preferences > Mouse from the main menu bar to launch Mouse Preferences. In the Buttons tab, click the Left-handed mouse check box and click Close to switch the primary mouse button from the left to the right (making the mouse suitable for use in the left hand).

  • Page 8: Notes And Warnings

    Introduction Output sent to a terminal is set in Mono-spaced Roman and presented thus: books Desktop documentation drafts photos stuff books_tests Desktop1 downloads images notes scripts svgs Source-code listings are also set in Mono-spaced Roman but are presented and highlighted as follows: package org.jboss.book.jca.ex1;...

  • Page 9: Feedback

    2. Feedback If you spot a typo, or if you have thought of a way to make this document better, we would love to hear from you. Please submit a report in Bugzilla (http://bugzilla.redhat.com/bugzilla/) against the component rh-cs-en. Be sure to mention the document's identifier: Cluster_Suite_Overview(EN)-4.8 (2009-04-24:T15:25)

  • Page 11: Red Hat Cluster Suite Overview

    Chapter 1. Red Hat Cluster Suite Overview Clustered systems provide reliability, scalability, and availability to critical production services. Using Red Hat Cluster Suite, you can create a cluster to suit your needs for performance, high availability, load balancing, scalability, file sharing, and economy. This chapter provides an overview of Red Hat Cluster Suite components and functions, and consists of the following sections: Section 1.1, “Cluster Basics”...

  • Page 12: Red Hat Cluster Suite Introduction

    Chapter 1. Red Hat Cluster Suite Overview Load-balancing clusters dispatch network service requests to multiple cluster nodes to balance the request load among the cluster nodes. Load balancing provides cost-effective scalability because you can match the number of nodes according to load requirements. If a node in a load-balancing cluster becomes inoperative, the load-balancing software detects the failure and redirects requests to other cluster nodes.
  • Page 13 Red Hat Cluster Suite Introduction Note When you create or modify a CLVM volume for a clustered environment, you must ensure that you are running the clvmd daemon. For further information, refer to Section 1.6, “Cluster Logical Volume Manager”. • Global Network Block Device (GNBD) — An ancillary component of GFS that exports block-level storage to Ethernet.

  • Page 14: Cluster Infrastructure

    Chapter 1. Red Hat Cluster Suite Overview 1.3. Cluster Infrastructure The Red Hat Cluster Suite cluster infrastructure provides the basic functions for a group of computers (called nodes or members) to work together as a cluster. Once a cluster is formed using the cluster infrastructure, you can use other Red Hat Cluster Suite components to suit your clustering needs (for example, setting up a cluster for sharing files on a GFS file system or setting up service failover).
  • Page 15 Cluster Management • Configured with one GULM server — Quorum equals one GULM server. • Configured with three GULM servers — Quorum equals two GULM servers. • Configured with five GULM servers — Quorum equals three GULM servers. The cluster manager keeps track of membership by monitoring heartbeat messages from other cluster nodes.

  • Page 16: Lock Management

    Chapter 1. Red Hat Cluster Suite Overview Figure 1.3. GULM Overview 1.3.2. Lock Management Lock management is a common cluster-infrastructure service that provides a mechanism for other cluster infrastructure components to synchronize their access to shared resources. In a Red Hat cluster, one of the following Red Hat Cluster Suite components operates as the lock manager: DLM (Distributed Lock Manager) or GULM (Grand Unified Lock Manager).
  • Page 17 Fencing what actions to take — that is, they perform any recovery that needs to done. For example, DLM and GFS (in a cluster configured with CMAN/DLM), when notified of a node failure, suspend activity until they detect that the fencing program has completed fencing the failed node. Upon confirmation that the failed node is fenced, DLM and GFS perform recovery.
  • Page 18 Chapter 1. Red Hat Cluster Suite Overview Figure 1.4. Power Fencing Example...
  • Page 19 Fencing Figure 1.5. Fibre Channel Switch Fencing Example Specifying a fencing method consists of editing a cluster configuration file to assign a fencing-method name, the fencing agent, and the fencing device for each node in the cluster. Note Other fencing parameters may be necessary depending on the type of cluster manager (either CMAN or GULM) selected in a cluster.
  • Page 20 Chapter 1. Red Hat Cluster Suite Overview Figure 1.6. Fencing a Node with Dual Power Supplies...

  • Page 21: Cluster Configuration System

    Cluster Configuration System Figure 1.7. Fencing a Node with Dual Fibre Channel Connections You can configure a node with one fencing method or multiple fencing methods. When you configure a node for one fencing method, that is the only fencing method available for fencing that node. When you configure a node for multiple fencing methods, the fencing methods are cascaded from one fencing method to another according to the order of the fencing methods specified in the cluster configuration file.
  • Page 22 Chapter 1. Red Hat Cluster Suite Overview cluster system administrator updates the configuration file in Node A, CCS propagates the update Figure 1.8, “CCS Overview”). from Node A to the other nodes in the cluster (refer to Figure 1.8. CCS Overview Other cluster components (for example, CMAN) access configuration information from the Figure 1.8, “CCS Overview”).

  • Page 23: High-Availability Service Management

    High-availability Service Management Figure 1.9. Accessing Configuration Information The cluster configuration file (/etc/cluster/cluster.conf) is an XML file that describes the following cluster characteristics: • Cluster name — Displays the cluster name, cluster configuration file revision level, locking type (either DLM or GULM), and basic fence timing properties used when a node joins a cluster or is fenced from the cluster.
  • Page 24 Chapter 1. Red Hat Cluster Suite Overview apparent interruption to cluster clients. Cluster-service failover can occur if a cluster node fails or if a cluster system administrator moves the service from one cluster node to another (for example, for a planned outage of a cluster node).
  • Page 25 High-availability Service Management Figure 1.10. Failover Domains Figure 1.11, “Web Server Cluster Service Example” shows an example of a high-availability cluster service that is a web server named "content-webserver". It is running in cluster node B and is in a failover domain that consists of nodes A, B, and D.

  • Page 26: Red Hat Gfs

    Chapter 1. Red Hat Cluster Suite Overview Figure 1.11. Web Server Cluster Service Example Clients access the cluster service through the IP address 10.10.10.201, enabling interaction with the web server application, httpd-content. The httpd-content application uses the gfs-content-webserver file system. If node B were to fail, the content-webserver cluster service would fail over to node D. If node D were not available or also failed, the service would fail over to node A.
  • Page 27 Red Hat GFS • Install and patch applications once for the entire cluster. • Eliminates the need for redundant copies of application data (duplication). • Enables concurrent read/write access to data by many clients. • Simplifies backup and disaster recovery (only one file system to back up or recover). •...

  • Page 28: Superior Performance And Scalability

    Chapter 1. Red Hat Cluster Suite Overview 1.5.1. Superior Performance and Scalability You can obtain the highest shared-file performance when applications access storage directly. The Figure 1.12, “GFS with a SAN” GFS SAN configuration in provides superior file performance for shared files and file systems.

  • Page 29: Economy And Performance

    Economy and Performance Figure 1.13. GFS and GNBD with a SAN 1.5.3. Economy and Performance Figure 1.14, “GFS and GNBD with Directly Connected Storage” shows how Linux client applications can take advantage of an existing Ethernet topology to gain shared access to all block storage devices.

  • Page 30: Cluster Logical Volume Manager

    Chapter 1. Red Hat Cluster Suite Overview 1.6. Cluster Logical Volume Manager The Cluster Logical Volume Manager (CLVM) provides a cluster-wide version of LVM2. CLVM provides the same capabilities as LVM2 on a single node, but makes the volumes available to all nodes in a Red Hat cluster.
  • Page 31 Cluster Logical Volume Manager Figure 1.15. CLVM Overview You can configure CLVM using the same commands as LVM2, using the LVM graphical user interface Figure 1.16, “LVM Graphical User Interface”), or using the storage configuration function of (refer to the Conga cluster configuration graphical user interface (refer to Figure 1.17, “Conga LVM Graphical User Interface”) .
  • Page 32 Chapter 1. Red Hat Cluster Suite Overview Figure 1.16. LVM Graphical User Interface...
  • Page 33 Cluster Logical Volume Manager Figure 1.17. Conga LVM Graphical User Interface...

  • Page 34: Global Network Block Device

    Chapter 1. Red Hat Cluster Suite Overview Figure 1.18. Creating Logical Volumes 1.7. Global Network Block Device Global Network Block Device (GNBD) provides block-device access to Red Hat GFS over TCP/IP. GNBD is similar in concept to NBD; however, GNBD is GFS-specific and tuned solely for use with GFS.

  • Page 35: Linux Virtual Server

    Linux Virtual Server Figure 1.19. GNBD Overview 1.8. Linux Virtual Server Linux Virtual Server (LVS) is a set of integrated software components for balancing the IP load across a set of real servers. LVS runs on a pair of equally configured computers: one that is an active LVS router and one that is a backup LVS router.
  • Page 36 Chapter 1. Red Hat Cluster Suite Overview Figure 1.20. Components of a Running LVS Cluster The pulse daemon runs on both the active and passive LVS routers. On the backup LVS router, pulse sends a heartbeat to the public interface of the active router to make sure the active LVS router is properly functioning.

  • Page 37: Two-Tier Lvs Topology

    Two-Tier LVS Topology • Synchronize the data across the real servers. • Add a third layer to the topology for shared data access. The first option is preferred for servers that do not allow large numbers of users to upload or change data on the real servers.
  • Page 38 Chapter 1. Red Hat Cluster Suite Overview Service requests arriving at an LVS router are addressed to a virtual IP address or VIP. This is a publicly-routable address that the administrator of the site associates with a fully-qualified domain name, such as www.example.com, and which is assigned to one or more virtual servers .

  • Page 39: Three-Tier Lvs Topology

    Three-Tier LVS Topology • Source Hash Scheduling — Distributes requests to the pool of real servers by looking up the source IP in a static hash table. This algorithm is for LVS routers with multiple firewalls. Also, the active LVS router dynamically monitors the overall health of the specific services on the real servers through simple send/expect scripts.

  • Page 40: Routing Methods

    Chapter 1. Red Hat Cluster Suite Overview Figure 1.22. Three-Tier LVS Topology This topology is suited well for busy FTP servers, where accessible data is stored on a central, highly available server and accessed by each real server via an exported NFS directory or Samba share. This topology is also recommended for websites that access a central, high-availability database for transactions.

  • Page 41: Direct Routing

    Routing Methods Figure 1.23. LVS Implemented with NAT Routing In the example, there are two NICs in the active LVS router. The NIC for the Internet has a real IP address on eth0 and has a floating IP address aliased to eth0:1. The NIC for the private network interface has a real IP address on eth1 and has a floating IP address aliased to eth1:1.
  • Page 42 Chapter 1. Red Hat Cluster Suite Overview outgoing packets through the LVS router. Direct routing reduces the possibility of network performance issues by relegating the job of the LVS router to processing incoming packets only. Figure 1.24. LVS Implemented with Direct Routing In a typical direct-routing LVS configuration, an LVS router receives incoming server requests through a virtual IP (VIP) and uses a scheduling algorithm to route the request to real servers.

  • Page 43: Persistence And Firewall Marks

    Persistence and Firewall Marks address of the LVS router must also be associated to a MAC. However, because both the LVS router and the real servers have the same VIP, the ARP request is broadcast to all the nodes associated with the VIP.

  • Page 44: Cluster Administration Tools

    Chapter 1. Red Hat Cluster Suite Overview 1.9. Cluster Administration Tools Red Hat Cluster Suite provides a variety of tools to configure and manage your Red Hat Cluster. This section provides an overview of the administration tools available with Red Hat Cluster Suite: Section 1.9.1, “Conga”...
  • Page 45 Conga Each luci instance has one user at initial installation — admin. Only the admin user may add systems to a luci server. Also, the admin user can create additional user accounts and determine which users are allowed to access clusters and computers registered in the luci database. It is possible to import users as a batch operation in a new luci server, just as it is possible to import clusters and computers.
  • Page 46 Chapter 1. Red Hat Cluster Suite Overview Figure 1.26. luci cluster Tab...

  • Page 47: Cluster Administration Gui

    Cluster Administration GUI Figure 1.27. luci storage Tab 1.9.2. Cluster Administration GUI This section provides an overview of the system-config-cluster cluster administration graphical user interface (GUI) available with Red Hat Cluster Suite. The GUI is for use with the cluster Section 1.3, infrastructure and the high-availability service management components (refer to “Cluster Infrastructure”...
  • Page 48 Chapter 1. Red Hat Cluster Suite Overview Figure 1.28. Cluster Configuration Tool The Cluster Configuration Tool represents cluster configuration components in the configuration file (/etc/cluster/cluster.conf) with a hierarchical graphical display in the left panel. A triangle icon to the left of a component name indicates that the component has one or more subordinate components assigned to it.

  • Page 49: Cluster Status Tool

    Cluster Administration GUI Fence devices must be defined before you can configure fencing (with the Manage Fencing For This Node button) for each node. • Managed Resources — Displays failover domains, resources, and services. • Failover Domains — For configuring one or more subsets of cluster nodes used to run a high- availability service in the event of a node failure.

  • Page 50: Command Line Administration Tools

    Chapter 1. Red Hat Cluster Suite Overview Figure 1.29. Cluster Status Tool The nodes and services displayed in the Cluster Status Tool are determined by the cluster configuration file (/etc/cluster/cluster.conf). You can use the Cluster Status Tool to enable, disable, restart, or relocate a high-availability service. 1.9.3.

  • Page 51: Linux Virtual Server Administration Gui

    Linux Virtual Server Administration GUI Command Line Used With Purpose Tool Cluster ccs_tool is a program for making online updates to the ccs_tool — Cluster Infrastructure cluster configuration file. It provides the capability to create Configuration and modify cluster infrastructure components (for example, System Tool creating a cluster, adding and removing a node).

  • Page 52: Control/Monitoring

    Chapter 1. Red Hat Cluster Suite Overview Starting the Piranha Configuration Tool causes the Piranha Configuration Tool welcome page to Figure 1.30, “The Welcome Panel”). Logging in to the welcome page provides be displayed (refer to access to the four main screens or panels: CONTROL/MONITORING, GLOBAL SETTINGS, REDUNDANCY, and VIRTUAL SERVERS.

  • Page 53: Global Settings

    GLOBAL SETTINGS Figure 1.31. The CONTROL/MONITORING Panel Auto update Enables the status display to be updated automatically at a user-configurable interval set in the Update frequency in seconds text box (the default value is 10 seconds). It is not recommended that you set the automatic update to an interval less than 10 seconds. Doing so may make it difficult to reconfigure the Auto update interval because the page will update too frequently.
  • Page 54 Chapter 1. Red Hat Cluster Suite Overview Figure 1.32. The GLOBAL SETTINGS Panel The top half of this panel sets up the primary LVS router's public and private network interfaces. Primary server public IP The publicly routable real IP address for the primary LVS node. Primary server private IP The real IP address for an alternative network interface on the primary LVS node.

  • Page 55: Redundancy

    REDUNDANCY NAT Router device Defines the device name of the network interface for the floating IP address, such as eth1:1. 1.10.3. REDUNDANCY The REDUNDANCY panel allows you to configure of the backup LVS router node and set various heartbeat monitoring options. Figure 1.33.

  • Page 56: Virtual Servers

    Chapter 1. Red Hat Cluster Suite Overview Assume dead after (seconds) If the primary LVS node does not respond after this number of seconds, then the backup LVS router node will initiate failover. Heartbeat runs on port Sets the port at which the heartbeat communicates with the primary LVS node. The default is set to 539 if this field is left blank.

  • Page 57: The Virtual Server Subsection

    VIRTUAL SERVERS To enable or disable a virtual server in the table click its radio button and click the (DE)ACTIVATE button. After adding a virtual server, you can configure it by clicking the radio button to its left and clicking the EDIT button to display the VIRTUAL SERVER subsection.

  • Page 58: Virtual Ip Address

    Chapter 1. Red Hat Cluster Suite Overview Protocol Provides a choice of UDP or TCP, in a drop-down menu. Virtual IP Address The virtual server's floating IP address. Virtual IP Network Mask The netmask for this virtual server, in the drop-down menu. Firewall Mark For entering a firewall mark integer value when bundling multi-port protocols or creating a multi- port virtual server for separate, but related protocols.

  • Page 59: Real Server Subsection

    VIRTUAL SERVERS 1.10.4.2. REAL SERVER Subsection Clicking on the REAL SERVER subsection link at the top of the panel displays the EDIT REAL SERVER subsection. It displays the status of the physical server hosts for a particular virtual service. Figure 1.36. The REAL SERVER Subsection Click the ADD button to add a new server.
  • Page 60 Chapter 1. Red Hat Cluster Suite Overview Figure 1.37. The REAL SERVER Configuration Panel This panel consists of three entry fields: Name A descriptive name for the real server. Note This name is not the hostname for the machine, so make it descriptive and easily identifiable.

  • Page 61: Edit Monitoring Scripts Subsection

    VIRTUAL SERVERS 1.10.4.3. EDIT MONITORING SCRIPTS Subsection Click on the MONITORING SCRIPTS link at the top of the page. The EDIT MONITORING SCRIPTS subsection allows the administrator to specify a send/expect string sequence to verify that the service for the virtual server is functional on each real server. It is also the place where the administrator can specify customized scripts to check services requiring dynamically changing data.
  • Page 62 Chapter 1. Red Hat Cluster Suite Overview Send A string for the nanny daemon to send to each real server in this field. By default the send field is completed for HTTP. You can alter this value depending on your needs. If you leave this field blank, the nanny daemon attempts to open the port and assume the service is running if it succeeds.

  • Page 63: Red Hat Cluster Suite Component Summary

    Chapter 2. Red Hat Cluster Suite Component Summary This chapter provides a summary of Red Hat Cluster Suite components and consists of the following sections: Section 2.1, “Cluster Components” • Section 2.2, “Man Pages” • Section 2.3, “Compatible Hardware” • 2.1.
  • Page 64 Chapter 2. Red Hat Cluster Suite Component Summary Function Components Description Diagnostic and testing command that ccs_test is used to retrieve information from configuration files through ccsd. CCS daemon that runs on all cluster ccsd nodes and provides configuration file data to cluster software.
  • Page 65 Cluster Components Function Components Description Fence agent for McData Fibre Channel fence_mcdata switch. Fence agent for Vixel Fibre Channel fence_vixel switch. Fence agent for SANBox2 Fibre Channel fence_sanbox2 switch. Fence agent for HP ILO interfaces fence_ilo (formerly fence_rib). I/O Fencing agent for IBM RSA II. fence_rsa Fence agent used with GNBD storage.
  • Page 66 Chapter 2. Red Hat Cluster Suite Component Summary Function Components Description Command that grows a mounted GFS gfs_grow file system. Command that adds journals to a gfs_jadd mounted GFS file system. Command that creates a GFS file gfs_mkfs system on a storage device. Command that manages quotas on a gfs_quota mounted GFS file system.

  • Page 67: Piranha Configuration Tool

    Cluster Components Function Components Description ha/lvs.cf. On the active LVS router, pulse starts the LVS daemon. On the backup router, pulse determines the health of the active router by executing a simple heartbeat at a user-configurable interval. If the active LVS router fails to respond after a user-configurable interval, it initiates failover.

  • Page 68: Man

    Chapter 2. Red Hat Cluster Suite Component Summary Function Components Description tool to maintain the /etc/sysconfig/ ha/lvs.cf LVS configuration file. This program sends out ARP broadcasts send_arp when the floating IP address changes from one node to another during failover. Quorum Disk A disk-based quorum daemon for qdisk...
  • Page 69 Man Pages • fence_ipmilan (8) - I/O Fencing agent for machines controlled by IPMI over LAN • fence_manual (8) - program run by fenced as a part of manual I/O Fencing • fence_mcdata (8) - I/O Fencing agent for McData FC switches •...

  • Page 70: Compatible Hardware

    • send_arp (8) - tool to notify network of a new IP address / MAC address mapping 2.3. Compatible Hardware For information about hardware that is compatible with Red Hat Cluster Suite components (for example, supported fence devices, storage devices, and Fibre Channel switches), refer to the hardware configuration guidelines at http://www.redhat.com/cluster_suite/hardware/.

  • Page 71: Revision History

    Appendix A. Revision History Revision 1.0 Fri Apr 24 2009...

  • Page 73: Index

    Index performance, 17 scalability, 17 Piranha Configuration Tool about this document CONTROL/MONITORING, 42 other Red Hat Enterprise Linux documents, v EDIT MONITORING SCRIPTS Subsection, 51 GLOBAL SETTINGS, 43 login panel, 42 cluster necessary software, 41 displaying status, 40 REAL SERVER subsection, 49 cluster administration REDUNDANCY, 45 displaying cluster and service status, 40...

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