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  • Page 1 Red Hat Cluster Suite for RHEL 4 Overview...
  • Page 2 All other trademarks referenced herein are the property of their respective owners. The GPG fingerprint of the security@redhat.com key is: CA 20 86 86 2B D6 9D FC 65 F6 EC C4 21 91 80 CD DB 42 A6 0E...

  • Page 3: Table Of Contents

    Table of Contents About This Document......................i 1. Document Conventions ..................i 2. Feedback ......................v 1. Red Hat Cluster Suite Overview ..................1 1.1. Cluster Basics....................1 1.2. Red Hat Cluster Suite Introduction ..............2 1.3. Cluster Infrastructure ..................4 1.3.1. Cluster Management ................4 1.3.2.

  • Page 5: About This Document

    Red Hat Cluster Suite documentation and other Red Hat documents are available in HTML, PDF, and RPM versions on the Red Hat Enterprise Linux Documentation CD and online at the following location: http://www.redhat.com/docs/ 1. Document Conventions In this manual, certain words are represented in different fonts, typefaces, sizes, and weights.
  • Page 6 About This Document contains words that would be displayed in a different style on their own (such as file names). In these cases, they are considered to be part of the command, so the entire phrase is displayed as a command. For example: Use the command to view the contents of a file, named cat testfile...
  • Page 7 About This Document top level of a menu on a GUI screen or window A word in this style indicates that the word is the top level of a pulldown menu. If you click on the word on the GUI screen, the rest of the menu should appear. For example: Under File on a GNOME terminal, the New Tab option allows you to open multiple shell prompts in the same window.
  • Page 8 About This Document <replaceable> Text used in examples that is meant to be replaced with data provided by the user is displayed in this style. In the following example, <version-number> is dis- played in this style: The directory for the kernel source is /usr/src/kernels/ <...

  • Page 9: 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 Be sure to mention the document’s identifier:...
  • Page 10 About This Document...

  • Page 11: Red Hat Cluster Suite Overview

    Chapter 1. Red Hat Cluster Suite Overview Clustered systems provide reliability, scalability, and availability to critical production ser- vices. Using Red Hat Cluster Suite, you can create a cluster to suit your needs for perfor- mance, high availability, load balancing, scalability, file sharing, and economy. This chap- ter 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 High-availability clusters provide continuous availability of services by eliminating single points of failure and by failing over services from one cluster node to another in case a node becomes inoperative. Typically, services in a high-availability cluster read and write data (via read-write mounted file systems).
  • Page 13 Chapter 1. Red Hat Cluster Suite Overview Cluster administration tools — Configuration and management tools for setting up, configuring, • and managing a Red Hat cluster. The tools are for use with the Cluster Infrastructure components and with the High-availability and Service Management components. Linux Virtual Server (LVS) —...

  • 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 Chapter 1. Red Hat Cluster Suite Overview Note In a CMAN cluster, by default each node has one quorum vote for establishing quorum. Optionally, you can configure each node to have more than one vote. In a GULM cluster, the quorum consists of a majority of nodes designated as GULM servers according to the number of GULM servers configured: Configured with one GULM server —...

  • 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 Man- ager).
  • Page 17 Chapter 1. Red Hat Cluster Suite Overview Configured with CMAN/DLM — , the fence daemon, performs fencing. • fenced Configured with GULM servers — GULM performs fencing. • When the cluster manager determines that a node has failed, it communicates to other cluster-infrastructure components that the node has failed.
  • Page 18 Chapter 1. Red Hat Cluster Suite Overview Figure 1-4. Power Fencing Example Figure 1-5. Fibre Channel Switch Fencing Example...
  • Page 19 Chapter 1. Red Hat Cluster Suite Overview 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 clus- ter. Note Other fencing parameters may be necessary depending on the type of cluster manager (either CMAN or GULM) selected in a cluster.

  • Page 20: Cluster Configuration System

    Chapter 1. Red Hat Cluster Suite Overview 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.
  • Page 21 Chapter 1. Red Hat Cluster Suite Overview Figure 1-8. CCS Overview Other cluster components (for example, CMAN) access configuration information from the configuration file through CCS (refer to Figure 1-8). Figure 1-9. Accessing Configuration Information...

  • Page 22: High-Availability Service Management

    Chapter 1. Red Hat Cluster Suite Overview The cluster configuration file ( ) is an XML file that de- /etc/cluster/cluster.conf scribes the following cluster characteristics: Cluster name — Displays the cluster name, cluster configuration file revision level, lock- • ing type (either DLM or GULM), and basic fence timing properties used when a node joins a cluster or is fenced from the cluster.
  • Page 23 Chapter 1. Red Hat Cluster Suite Overview cluster service can start on any cluster node in the event no member of the failover domain is available.) In Figure 1-10, Failover Domain 1 is configured to restrict failover within that domain; therefore, Cluster Service X can only fail over between Node A and Node B.

  • Page 24: Red Hat Gfs

    Chapter 1. Red Hat Cluster Suite Overview Figure 1-11 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. In addition, the failover domain is configured with a failover priority to fail over to node D before node A and to restrict failover to nodes only in that failover domain.
  • Page 25 Chapter 1. Red Hat Cluster Suite Overview 1.5. Red Hat GFS Red Hat GFS is a cluster file system that allows a cluster of nodes to simultaneously access a block device that is shared among the nodes. GFS is a native file system that interfaces directly with the VFS layer of the Linux kernel file-system interface.

  • Page 26: Superior Performance And Scalability

    Chapter 1. Red Hat Cluster Suite Overview You can deploy GFS in a variety of configurations to suit your needs for performance, scalability, and economy. For superior performance and scalability, you can deploy GFS in a cluster that is connected directly to a SAN. For more economical needs, you can deploy GFS in a cluster that is connected to a LAN with servers that use GNBD (Global Network Block Device) or to iSCSI (Internet Small Computer System Interface) devices.

  • Page 27: Performance, Scalability, Moderate Price

    Chapter 1. Red Hat Cluster Suite Overview Figure 1-12. GFS with a SAN 1.5.2. Performance, Scalability, Moderate Price Multiple Linux client applications on a LAN can share the same SAN-based data as shown in Figure 1-13. SAN block storage is presented to network clients as block storage devices by GNBD servers.

  • Page 28: Economy And Performance

    Chapter 1. Red Hat Cluster Suite Overview Figure 1-13. GFS and GNBD with a SAN 1.5.3. Economy and Performance Figure 1-14 shows how Linux client applications can take advantage of an existing Ethernet topology to gain shared access to all block storage devices. Client data files and file systems can be shared with GFS on each client.

  • Page 29: Cluster Logical Volume Manager

    Chapter 1. Red Hat Cluster Suite Overview Figure 1-14. GFS and GNBD with Directly Connected Storage 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 30 Chapter 1. Red Hat Cluster Suite Overview Note Using CLVM requires minor changes to for cluster-wide locking. /etc/lvm/lvm.conf Figure 1-15. CLVM Overview You can configure CLVM using the same commands as LVM2 or by using the LVM graph- ical user interface (refer to Figure 1-16). Figure 1-17 shows the basic concept of creating logical volumes from Linux partitions and shows the commands used to create logical volumes.
  • Page 31 Chapter 1. Red Hat Cluster Suite Overview Figure 1-16. LVM Graphical User Interface Figure 1-17. Creating Logical Volumes...

  • Page 32: Global Network Block Device

    Chapter 1. Red Hat Cluster Suite Overview 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. GNBD is useful when the need for more robust technologies — Fibre Channel or single-initiator SCSI —...
  • Page 33 Chapter 1. Red Hat Cluster Suite Overview To balance the load across the real servers. • To check the integrity of the services on each real server. • The backup LVS router monitors the active LVS router and takes over from it in case the active LVS router fails.

  • Page 34: Two-Tier Lvs Topology

    Chapter 1. Red Hat Cluster Suite Overview router via both the public and private network interfaces to shut down the daemon on the active LVS router, and starts the daemon on the backup LVS router to accept requests for the configured virtual servers. To an outside user accessing a hosted service (such as a website or database application), LVS appears as one server.
  • Page 35 Chapter 1. Red Hat Cluster Suite Overview Figure 1-20. Two-Tier LVS Topology 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 36 Chapter 1. Red Hat Cluster Suite Overview Weighted Round-Robin Scheduling — Distributes each request sequentially around a • pool of real servers but gives more jobs to servers with greater capacity. Capacity is in- dicated by a user-assigned weight factor, which is then adjusted up or down by dynamic load information.

  • Page 37: Three-Tier Lvs Topology

    Chapter 1. Red Hat Cluster Suite Overview of the active LVS router. During failover, the backup LVS router takes over the VIP ad- dresses serviced by the failed router using a technique known as ARP spoofing — where the backup LVS router announces itself as the destination for IP packets addressed to the failed node.
  • Page 38 Chapter 1. Red Hat Cluster Suite Overview Figure 1-21. Three-Tier LVS Topology This topology is suited well for busy FTP servers, where accessible data is stored on a cen- tral, highly available server and accessed by each real server via an exported NFS direc- tory or Samba share.

  • Page 39: Routing Methods

    Chapter 1. Red Hat Cluster Suite Overview 1.8.3. Routing Methods You can use Network Address Translation (NAT) routing or direct routing with LVS. The following sections briefly describe NAT routing and direct routing with LVS. 1.8.3.1. NAT Routing Figure 1-22, illustrates LVS using NAT routing to move requests between the Internet and a private network.
  • Page 40 Chapter 1. Red Hat Cluster Suite Overview IP address to its physical device on the LVS router nodes, having more than two NICs is not a requirement. Using this topology, the active LVS router receives the request and routes it to the ap- propriate server.
  • Page 41 Chapter 1. Red Hat Cluster Suite Overview Figure 1-23. LVS Implemented with Direct Routing In a typical direct-routing LVS configuration, an LVS router receives incoming server re- quests through a virtual IP (VIP) and uses a scheduling algorithm to route the request to real servers.

  • Page 42: Persistence And Firewall Marks

    Chapter 1. Red Hat Cluster Suite Overview The issue with ARP requests in a direct-routing LVS configuration is that because a client request to an IP address must be associated with a MAC address for the request to be han- dled, the virtual IP address of the LVS router must also be associated to a MAC.

  • Page 43: Cluster Administration Gui

    Chapter 1. Red Hat Cluster Suite Overview 1.8.4.2. Firewall Marks Firewall marks are an easy and efficient way to a group ports used for a protocol or group of related protocols. For example, if LVS is deployed to run an e-commerce site, firewall marks can be used to bundle HTTP connections on port 80 and secure, HTTPS connections on port 443.

  • Page 44: Cluster Configuration Tool

    Chapter 1. Red Hat Cluster Suite Overview Command Used With Purpose Line Tool — Cluster is a program for making online updates ccs_tool ccs_tool Cluster Infrastructure to the cluster configuration file. It provides the Configuration capability to create and modify cluster System Tool infrastructure components (for example, creating a cluster, adding and removing a node).
  • Page 45 Chapter 1. Red Hat Cluster Suite Overview 1.9.1. Cluster Configuration Tool You can access the Cluster Configuration Tool (Figure 1-24) through the Cluster Con- figuration tab in the Cluster Administration GUI. Figure 1-24. Cluster Configuration Tool The Cluster Configuration Tool represents cluster configuration components in the con- figuration file ( ) with a hierarchical graphical display in /etc/cluster/cluster.conf...
  • Page 46 Chapter 1. Red Hat Cluster Suite Overview Fence Devices — Displays fence devices. Fence devices are represented as subordinate • elements under Fence Devices. Using configuration buttons at the bottom of the right frame (below Properties), you can add fence devices, delete fence devices, and edit fence-device properties.
  • Page 47 Chapter 1. Red Hat Cluster Suite Overview Figure 1-25. Cluster Configuration Structure...

  • Page 48: Cluster Status Tool

    Chapter 1. Red Hat Cluster Suite Overview 1.9.2. Cluster Status Tool You can access the Cluster Status Tool (Figure 1-26) through the Cluster Management tab in Cluster Administration GUI. Figure 1-26. Cluster Status Tool The nodes and services displayed in the Cluster Status Tool are determined by the cluster ).
  • Page 49 Chapter 1. Red Hat Cluster Suite Overview (Relocating a service to its current node — that is, dragging a service to its current node and dropping the service onto that node — restarts the service.) The following tables describe the members and services status information displayed by the Cluster Status Tool.

  • Page 50: Linux Virtual Server Administration Gui

    Chapter 1. Red Hat Cluster Suite Overview 1.10. Linux Virtual Server Administration GUI This section provides an overview of the LVS configuration tool available with Red Hat Cluster Suite — the Piranha Configuration Tool. The Piranha Configuration Tool is a Web-browser graphical user interface (GUI) that provides a structured approach to creating the configuration file for LVS —...

  • Page 51: Global Settings

    Chapter 1. Red Hat Cluster Suite Overview Figure 1-28. 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.
  • Page 52 Chapter 1. Red Hat Cluster Suite Overview Figure 1-29. 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 53: Redundancy

    Chapter 1. Red Hat Cluster Suite Overview NAT Router netmask If the NAT router’s floating IP needs a particular netmask, select it from drop-down list. NAT Router device Defines the device name of the network interface for the floating IP address, such as eth1:1.

  • Page 54: Virtual Servers

    Chapter 1. Red Hat Cluster Suite Overview Redundant server private IP The backup router’s private real IP address. The rest of the panel is for configuring the heartbeat channel, which is used by the backup node to monitor the primary node for failure. Heartbeat Interval (seconds) Sets the number of seconds between heartbeats —...
  • Page 55 Chapter 1. Red Hat Cluster Suite Overview Figure 1-31. The VIRTUAL SERVERS Panel Each server displayed in the VIRTUAL SERVERS panel can be configured on subsequent screens or subsections. To add a service, click the ADD button. To remove a service, select it by clicking the radio button next to the virtual server and click the DELETE button.
  • Page 56 Chapter 1. Red Hat Cluster Suite Overview Figure 1-32. The VIRTUAL SERVERS Subsection Name A descriptive name to identify the virtual server. This name is not the hostname for the machine, so make it descriptive and easily identifiable. You can even reference the protocol used by the virtual server, such as HTTP.
  • Page 57 Chapter 1. Red Hat Cluster Suite Overview Firewall Mark For entering a firewall mark integer value when bundling multi-port protocols or cre- ating a multi-port virtual server for separate, but related protocols. Device The name of the network device to which you want the floating IP address defined in the Virtual IP Address field to bind.
  • Page 58 Chapter 1. Red Hat Cluster Suite Overview Persistence Network Mask To limit persistence to particular subnet, select the appropriate network mask from the drop-down menu. 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.
  • Page 59 Chapter 1. Red Hat Cluster Suite Overview Figure 1-34. The REAL SERVER Configuration Panel This panel consists of three entry fields: Name A descriptive name for the real server. This name is not the hostname for the machine, so make it descriptive and easily identifiable.
  • Page 60 Chapter 1. Red Hat Cluster Suite Overview 1.10.4.3. EDIT MONITORING SCRIPTS Subsection Click on the MONITORING SCRIPTS link at the top of the page. The EDIT MONI- TORING 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 61 Chapter 1. Red Hat Cluster Suite Overview Send A string for the daemon to send to each real server in this field. By default the nanny send field is completed for HTTP. You can alter this value depending on your needs. If you leave this field blank, the daemon attempts to open the port and assume nanny...
  • Page 62 Chapter 1. Red Hat Cluster Suite Overview...

  • 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 • 2.1. Cluster Components Table 2-1 summarizes cluster components. Function Components Description...
  • Page 64 Chapter 2. Red Hat Cluster Suite Component Summary Function Components Description Cluster is part of the Cluster ccs_tool ccs_tool Configuration Configuration System (CCS). It is System (CCS) used to make online updates of CCS configuration files. Additionally, it can be used to upgrade cluster configuration files from CCS archives created with GFS 6.0 (and earlier) to the XML...
  • Page 65 Chapter 2. Red Hat Cluster Suite Component Summary Function Components Description Daemon used to handle user clurgmgrd service requests including service start, service disable, service relocate, and service restart Daemon used to handle Clustered clurmtabd NFS mount tables Fence Command used by fence_node lock_gulmd when a fence operation is required.
  • Page 66 Chapter 2. Red Hat Cluster Suite Component Summary Function Components Description Fence agent used with Egenera fence_egenera BladeFrame system. Fence agent used with fence_xcat xCAT-managed cluster. Fence agent for manual interaction. fence_manual NOTE This component is not supported for production environments.
  • Page 67 Chapter 2. Red Hat Cluster Suite Component Summary Function Components Description Command that configures or tunes gfs_tool a GFS file system. This command can also gather a variety of information about the file system. Implements a pluggable lock lock_harness.ko module interface for GFS that allows for a variety of locking mechanisms to be used (for example, the DLM lock module,...
  • Page 68 Chapter 2. Red Hat Cluster Suite Component Summary Function Components Description This is the controlling process pulse which starts all other daemons related to LVS routers. At boot time, the daemon is started by the /etc/rc.d/init.d/pulse script. It then reads the configuration file /etc/sysconfig/ha/lvs.cf On the active LVS router,...

  • Page 69: Man

    Chapter 2. Red Hat Cluster Suite Component Summary Function Components Description monitoring daemon nanny nanny runs on the active LVS router. Through this daemon, the active LVS router determines the health of each real server and, optionally, monitors its workload. A separate process runs for each service defined on each real server.
  • Page 70 Chapter 2. Red Hat Cluster Suite Component Summary cluster.conf [cluster] (5) - The configuration file for cluster products • QDisk 1.0 [qdisk] (5) - a disk-based quorum daemon for CMAN / Linux-Cluster • fence_node (8) - A program which performs I/O fencing on a single node •...
  • Page 71 Chapter 2. Red Hat Cluster Suite Component Summary gfs_quota (8) - Manipulate GFS disk quotas • gfs_tool (8) - interface to gfs ioctl calls • Cluster Logical Volume Manager • clvmd (8) - cluster LVM daemon • lvm (8) - LVM2 tools •...
  • Page 72 Chapter 2. Red Hat Cluster Suite Component Summary...

  • Page 73: Index

    Index members status table, 39 about this document, i other Red Hat Enterprise Linux documents, i routing methods, LVS, 29 network address translation (see NAT) cluster displaying status, 39 cluster administration overview displaying cluster and service status, 39 economy, 15 cluster components table, 53 performance, 15 Cluster Configuration Tool...
  • Page 74 services status table, 39 table command line tools, 33 tables cluster components, 53 members status, 39 services status, 39...

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