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Red Hat CLUSTER SUITE FOR ENTERPRISE LINUX 4.5 Overview

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Red Hat Cluster Suite Overview
Red Hat Cluster Suite for
Red Hat Enterprise Linux
4.5
4.5
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Summary of Contents for Red Hat CLUSTER SUITE FOR ENTERPRISE LINUX 4.5

  • Page 1 Red Hat Cluster Suite Overview Red Hat Cluster Suite for Red Hat Enterprise Linux ISBN: N/A Publication date:...
  • Page 2 Red Hat Cluster Suite Overview Red Hat Cluster Suite Overview provides an overview of Red Hat Cluster Suite for Red Hat Enterprise Linux 4.5.
  • Page 3 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 4 Red Hat Cluster Suite Overview...

  • Page 5: Table Of Contents

    Introduction ......................vii 1. Document Conventions ................viii 2. Feedback ...................... ix 1. Red Hat Cluster Suite Overview ................1 1. Cluster Basics ....................1 2. Red Hat Cluster Suite Introduction ..............2 3. Cluster Infrastructure ..................4 3.1. Cluster Management ................5 3.2.

  • Page 7: Introduction

    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 http://www.redhat.com/docs/. For more information about Red Hat Cluster Suite for Red Hat Enterprise Linux 4.5, refer to the following resources: •...

  • Page 8: Document Conventions

    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 http://www.redhat.com/docs/. 1. Document Conventions Certain words in this manual are represented in different fonts, styles, and weights. This highlighting indicates that the word is part of a specific category.

  • 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 Be sure to mention the document's identifier: sac_cl_over(EN)-4.5 (2008-06-02:T14:51)
  • Page 10 Introduction By mentioning this document's identifier, we know exactly which version of the guide you have. If you have a suggestion for improving the documentation, try to be as specific as possible. If you have found an error, please include the section number and some of the surrounding text so we can find it easily.

  • 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: •...

  • 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 Red Hat Cluster Suite Introduction Infrastructure components, the High-availability and Service Management components, and storage. • Linux Virtual Server (LVS) — Routing software that provides IP-Load-balancing. LVS runs in a pair of redundant servers that distributes client requests evenly to real servers that are behind the LVS servers.

  • Page 14: Cluster Infrastructure

    Chapter 1. Red Hat Cluster Suite Overview Figure 1.1. Red Hat Cluster Suite Introduction Note Figure 1.1, “Red Hat Cluster Suite Introduction” includes GFS, CLVM, and GNBD, which are components that are part of an optional package and not part of Red Hat Cluster Suite.

  • Page 15: Cluster Management

    Cluster Management • Fencing • Cluster configuration management 3.1. Cluster Management Cluster management manages cluster quorum and cluster membership. One of the following Red Hat Cluster Suite components performs cluster management: CMAN (an abbreviation for cluster manager) or GULM (Grand Unified Lock Manager). CMAN operates as the cluster manager if a cluster is configured to use DLM (Distributed Lock Manager) as the lock manager.
  • Page 16 Chapter 1. Red Hat Cluster Suite Overview • 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 17: Lock Management

    Lock Management Figure 1.3. GULM Overview 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 18 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 19 Fencing Figure 1.4. Power Fencing Example...
  • Page 20 Chapter 1. Red Hat Cluster Suite Overview 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 21 Fencing Channel Connections”). Figure 1.6. Fencing a Node with Dual Power Supplies...

  • Page 22: 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 23 Cluster Configuration System The Cluster Configuration System (CCS) manages the cluster configuration and provides configuration information to other cluster components in a Red Hat cluster. CCS runs in each cluster node and makes sure that the cluster configuration file in each cluster node is up to date. For example, if a cluster system administrator updates the configuration file in Node A, CCS propagates the update from Node A to the other nodes in the cluster (refer to Figure 1.8, “CCS...

  • Page 24: High-Availability Service Management

    Chapter 1. Red Hat Cluster Suite Overview Figure 1.9. Accessing Configuration Information The cluster configuration file ( ) is an XML file that describes the /etc/cluster/cluster.conf 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 25: Cluster Service

    High-availability Service Management High-availability service management provides the ability to create and manage high-availability cluster services in a Red Hat cluster. The key component for high-availability service management in a Red Hat cluster, , implements cold failover for off-the-shelf rgmanager applications.
  • Page 26 Chapter 1. Red Hat Cluster Suite Overview 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 27: Red Hat Gfs

    Red Hat GFS 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.
  • Page 28 Chapter 1. Red Hat Cluster Suite Overview uses a lock manager to coordinate I/O. When one node changes data on a GFS file system, that change is immediately visible to the other cluster nodes using that file system. Using Red Hat GFS, you can achieve maximum application uptime through the following benefits: •...

  • Page 29: Superior Performance And Scalability

    Superior Performance and Scalability • Section 5.1, “Superior Performance and Scalability” • Section 5.2, “Performance, Scalability, Moderate Price” • Section 5.3, “Economy and Performance” Note The GFS deployment examples reflect basic configurations; your needs might require a combination of configurations shown in the examples. 5.1.

  • Page 30: Economy And Performance

    Chapter 1. Red Hat Cluster Suite Overview Figure 1.13, “GFS and GNBD with a SAN”. SAN block storage is presented to network clients as block storage devices by GNBD servers. From the perspective of a client application, storage is accessed as if it were directly attached to the server in which the application is running. Stored data is actually on the SAN.

  • Page 31: Cluster Logical Volume Manager

    Cluster Logical Volume Manager Figure 1.14. GFS and GNBD with Directly Connected Storage 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 32 Chapter 1. Red Hat Cluster Suite Overview Shared storage for use in Red Hat Cluster Suite requires that you be running the cluster logical volume manager daemon ( ) or the High Availability Logical clvmd Volume Management agents (HA-LVM). If you are not able to use either the daemon or HA-LVM for operational reasons or because you do not have clvmd the correct entitlements, you must not use single-instance LVM on the shared...
  • Page 33 Cluster Logical Volume Manager Figure 1.17, “Conga LVM Graphical User Interface”) . Figure 1.18, “Creating Logical Volumes” shows the basic concept of creating logical volumes from Linux partitions and shows the commands used to create logical volumes. Figure 1.16. LVM Graphical User Interface...
  • Page 34 Chapter 1. Red Hat Cluster Suite Overview Figure 1.17. Conga LVM Graphical User Interface...

  • Page 35: Global Network Block Device

    Global Network Block Device Figure 1.18. Creating Logical Volumes 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 36: Linux Virtual Server

    Chapter 1. Red Hat Cluster Suite Overview Figure 1.19. GNBD Overview 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 37 Linux Virtual Server Figure 1.20. Components of a Running LVS Cluster daemon runs on both the active and passive LVS routers. On the backup LVS pulse router, sends a heartbeat to the public interface of the active router to make sure the pulse active LVS router is properly functioning.

  • Page 38: Two-Tier Lvs Topology

    Chapter 1. Red Hat Cluster Suite Overview To an outside user accessing a hosted service (such as a website or database application), LVS appears as one server. However, the user is actually accessing real servers behind the LVS routers. Because there is no built-in component in LVS to share the data among real servers, you have have two basic options: •...
  • Page 39 Two-Tier LVS Topology Figure 1.21. 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 40 Chapter 1. Red Hat Cluster Suite Overview • Round-Robin Scheduling — Distributes each request sequentially around a pool of real servers. Using this algorithm, all the real servers are treated as equals without regard to capacity or load. • Weighted Round-Robin Scheduling — Distributes each request sequentially around a pool of real servers but gives more jobs to servers with greater capacity.

  • Page 41: Three-Tier Lvs Topology

    Three-Tier LVS Topology The backup LVS router performs the role of a standby system. Periodically, the LVS routers exchange heartbeat messages through the primary external public interface and, in a failover situation, the private interface. Should the backup LVS router fail to receive a heartbeat message within an expected interval, it initiates a failover and assumes the role of the active LVS router.
  • Page 42 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.

  • Page 43: Routing Methods

    Routing Methods a Red Hat cluster, you can configure one high-availability cluster to serve both of these roles simultaneously. 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. 8.3.1.

  • Page 44: Direct Routing

    Chapter 1. Red Hat Cluster Suite Overview interface are taken over by the backup LVS router simultaneously. All the real servers on the private network use the floating IP for the NAT router as their default route to communicate with the active LVS router so that their abilities to respond to requests from the Internet is not impaired.
  • Page 45 Routing Methods 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. Each real server processes requests and sends responses directly to clients, bypassing the LVS routers.

  • Page 46: Persistence And Firewall Marks

    Chapter 1. Red Hat Cluster Suite Overview In typical situations, a client on the Internet sends a request to an IP address. Network routers typically send requests to their destination by relating IP addresses to a machine's MAC address with ARP. ARP requests are broadcast to all connected machines on a network, and the machine with the correct IP/MAC address combination receives the packet.

  • Page 47: Cluster Administration Tools

    Cluster Administration Tools 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 48 Chapter 1. Red Hat Cluster Suite Overview luci is accessible through a Web browser and provides three major functions that are accessible through the following tabs: • homebase — Provides tools for adding and deleting computers, adding and deleting users, and configuring user privileges.
  • Page 49 Conga Figure 1.25. luci homebase Tab Figure 1.26. luci cluster Tab...

  • Page 50: Cluster Administration Gui

    Chapter 1. Red Hat Cluster Suite Overview Figure 1.27. luci storage Tab 9.2. Cluster Administration GUI This section provides an overview of the cluster administration system-config-cluster graphical user interface (GUI) available with Red Hat Cluster Suite. The GUI is for use with the cluster infrastructure and the high-availability service management components (refer to Section 3, “Cluster Infrastructure”...

  • Page 51: Cluster Configuration Tool

    Cluster Administration GUI 9.2.1. Cluster Configuration Tool You can access the Cluster Configuration Tool (Figure 1.28, “Cluster Configuration Tool”) through the Cluster Configuration tab in the Cluster Administration GUI. Figure 1.28. Cluster Configuration Tool The Cluster Configuration Tool represents cluster configuration components in the configuration file ( ) with a hierarchical graphical display in the left /etc/cluster/cluster.conf...
  • Page 52 Chapter 1. Red Hat Cluster Suite Overview • Cluster Nodes — Displays cluster nodes. Nodes are represented by name as subordinate elements under Cluster Nodes. Using configuration buttons at the bottom of the right frame (below Properties), you can add nodes, delete nodes, edit node properties, and configure fencing methods for each node.

  • Page 53: Command Line Administration Tools

    Command Line Administration Tools You can access the Cluster Status Tool (Figure 1.29, “Cluster Status Tool”) through the Cluster Management tab in Cluster Administration GUI. Figure 1.29. Cluster Status Tool The nodes and services displayed in the Cluster Status Tool are determined by the cluster configuration file ( ).
  • Page 54 Chapter 1. Red Hat Cluster Suite Overview service management components. The command line tools are used by the Cluster Administration GUI and init scripts supplied by Red Hat. Table 1.1, “Command Line Tools” summarizes the command line tools. Command Line Used With Purpose Tool...

  • Page 55: Linux Virtual Server Administration Gui

    CONTROL/MONITORING 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 56 Chapter 1. Red Hat Cluster Suite Overview The CONTROL/MONITORING Panel displays runtime status. It displays the status of the pulse daemon, the LVS routing table, and the LVS-spawned processes. nanny 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).

  • Page 57: Global Settings

    GLOBAL SETTINGS administrative password for the Piranha Configuration Tool. 10.2. GLOBAL SETTINGS The GLOBAL SETTINGS panel is where the LVS administrator defines the networking details for the primary LVS router's public and private network interfaces. 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.

  • Page 58: Redundancy

    Chapter 1. Red Hat Cluster Suite Overview Selects select NAT routing. The next three fields are specifically for the NAT router's virtual network interface connected the private network with the real servers. NAT Router IP The private floating IP in this text field. This floating IP should be used as the gateway for the real servers.

  • Page 59: Virtual Servers

    VIRTUAL SERVERS Figure 1.33. The REDUNDANCY Panel Redundant server public IP The public real IP address for the backup LVS router. 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.
  • Page 60 Chapter 1. Red Hat Cluster Suite Overview Figure 1.34. 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 61 VIRTUAL SERVERS any of the subsections related to this virtual server, complete this page and click on the ACCEPT button. Figure 1.35. 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.

  • Page 62: Firewall Mark

    Chapter 1. Red Hat Cluster Suite Overview 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. 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 63: Real Server Subsection

    VIRTUAL SERVERS drop-down menu. 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.
  • Page 64 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. This name is not the hostname for the machine, so make it descriptive and easily identifiable.

  • Page 65: Edit Monitoring Scripts Subsection

    VIRTUAL SERVERS Weight An integer value indicating this host's capacity relative to that of other hosts in the pool. The value can be arbitrary, but treat it as a ratio in relation to other real servers. 10.4.3. EDIT MONITORING SCRIPTS Subsection Click on the MONITORING SCRIPTS link at the top of the page.
  • Page 66 Chapter 1. Red Hat Cluster Suite Overview dynamically changing data, such as HTTPS or SSL. To use this function, you must write a script that returns a textual response, set it to be executable, and type the path to it in the Sending Program field. Note If an external program is entered in the Sending Program field, then the Send field is ignored.

  • Page 67: 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 1, “Cluster Components” • Section 2, “Man Pages” • Section 3, “Compatible Hardware” 1.
  • Page 68 Chapter 2. Red Hat Cluster Suite Component Summary Function Components Description created with GFS 6.0 (and earlier) to the XML format configuration format used with this release of Red Hat Cluster Suite. Diagnostic and testing command that ccs_test is used to retrieve information from configuration files through ccsd CCS daemon that runs on all cluster...
  • Page 69 Cluster Components Function Components Description Fence agent for machines controlled fence_ipmilan by IPMI (Intelligent Platform Management Interface) over LAN. Fence agent for WTI power switch. fence_wti Fence agent for Brocade Fibre fence_brocade Channel switch. Fence agent for McData Fibre fence_mcdata Channel switch.
  • Page 70 Chapter 2. Red Hat Cluster Suite Component Summary Function Components Description cluster nodes for Distributed Lock Manager (DLM) support. GULM Server/daemon that runs on each lock_gulmd node and communicates with all nodes in GFS cluster. Library for GULM lock manager libgulm.so.xxx support Command that configures and...
  • Page 71 Cluster Components Function Components Description manager in Red Hat Cluster Suite. A lock module for use when GFS is lock_nolock.ko used as a local file system only. It plugs into the lock harness, and provides local lock_harness.ko locking. GNBD Kernel module that implements the gnbd.ko GNBD device driver on clients.

  • Page 72: Piranha Configuration Tool

    Chapter 2. Red Hat Cluster Suite Component Summary Function Components Description maintain the IPVS routing table, and assigns a process for each nanny configured LVS service. If nanny reports a real server is down, instructs the utility to remove ipvsadm the real server from the IPVS routing table.

  • Page 73: Man

    Man Pages 2. Man Pages This section lists man pages that are relevant to Red Hat Cluster Suite, as an additional resource. • Cluster Infrastructure • ccs_tool (8) - The tool used to make online updates of CCS config files •...
  • Page 74 Chapter 2. Red Hat Cluster Suite Component Summary • fence_rsa (8) - I/O Fencing agent for IBM RSA II • fence_sanbox2 (8) - I/O Fencing agent for QLogic SANBox2 FC switches • fence_scsi (8) - I/O fencing agent for SCSI persistent reservations •...

  • Page 75: Compatible Hardware

    • send_arp (8) - tool to notify network of a new IP address / MAC address mapping 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 77: Index

    routing methods, LVS, 33 Index network address translation (see NAT) overview economy, 18 about this document performance, 18 other Red Hat Enterprise Linux documents, scalability, 18 Piranha Configuration Tool cluster CONTROL/MONITORING, 45 displaying status, 43 EDIT MONITORING SCRIPTS Subsection, cluster administration displaying cluster and service status, 43 GLOBAL SETTINGS, 47 cluster component compatible hardware, 65...

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