Red Hat Cluster Suite Overview Red Hat Cluster Suite for Red Hat Enterprise Linux ISBN: N/A Publication date:...
Red Hat Cluster Suite Overview Red Hat Cluster Suite Overview provides an overview of Red Hat Cluster Suite for Red Hat Enterprise Linux 5.0.
All other trademarks referenced herein are the property of their respective owners. The GPG fingerprint of the firstname.lastname@example.org key is: CA 20 86 86 2B D6 9D FC 65 F6 EC C4 21 91 80 CD DB 42 A6 0E...
• Red Hat Cluster Suite Release Notes — Provides information about the current release of Red Hat Cluster Suite. 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/.
Introduction 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. The categories include the following: Courier font Courier font represents , and commands file names and paths prompts...
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)-5.0 (2008-06-01:T14:20)
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: •...
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).
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.
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.
Cluster Management • Fencing • Cluster configuration management 3.1. Cluster Management Cluster management manages cluster quorum and cluster membership. CMAN (an abbreviation for cluster manager) performs cluster management in Red Hat Cluster Suite for Red Hat Enterprise Linux 5. CMAN is a distributed cluster manager and runs in each cluster node; cluster management is distributed across all nodes in the cluster (refer to Figure 1.2, “CMAN/DLM...
Chapter 1. Red Hat Cluster Suite Overview Figure 1.2. CMAN/DLM 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, DLM (Distributed Lock Manager) is the lock manager. As implied in its name, DLM is a distributed lock manager and runs in each cluster node;...
Fencing fencing device. The fencing program makes a call to a fencing agent specified in the cluster configuration file. The fencing agent, in turn, fences the node via a fencing device. When fencing is complete, the fencing program notifies the cluster manager. Red Hat Cluster Suite provides a variety of fencing methods: •...
Chapter 1. Red Hat Cluster Suite Overview Figure 1.3. Power Fencing Example...
Fencing Figure 1.4. 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. The way in which a fencing method is specified depends on if a node has either dual power supplies or multiple paths to storage.
Chapter 1. Red Hat Cluster Suite Overview Figure 1.5. Fencing a Node with Dual Power Supplies...
Cluster Configuration System Figure 1.6. 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.
Chapter 1. Red Hat Cluster Suite Overview 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 1.7, “CCS...
High-availability Service Management Figure 1.8. 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, and basic fence timing properties used when a node joins a cluster or is fenced from the cluster.
Chapter 1. Red Hat Cluster Suite Overview 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.
High-availability Service Management Figure 1.9. Failover Domains Figure 1.10, “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. 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.
Chapter 1. Red Hat Cluster Suite Overview Figure 1.10. 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.
Red Hat GFS 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: •...
Chapter 1. Red Hat Cluster Suite Overview • 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.
Economy and Performance Figure 1.12, “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.
Chapter 1. Red Hat Cluster Suite Overview Figure 1.13. 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.
Cluster Logical Volume Manager 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...
Chapter 1. Red Hat Cluster Suite Overview Figure 1.16, “Conga LVM Graphical User Interface”) . Figure 1.17, “Creating Logical Volumes” shows the basic concept of creating logical volumes from Linux partitions and shows the commands used to create logical volumes. Figure 1.15.
Chapter 1. Red Hat Cluster Suite Overview Figure 1.17. 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.
Linux Virtual Server Figure 1.18. 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.
Chapter 1. Red Hat Cluster Suite Overview Figure 1.19. 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.
Two-Tier LVS Topology 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: •...
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 .
Two-Tier LVS Topology • 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.
Chapter 1. Red Hat Cluster Suite Overview 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.
Three-Tier LVS Topology Figure 1.21. 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.
Chapter 1. Red Hat Cluster Suite Overview 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.
Routing Methods 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.
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 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.
Persistence and Firewall Marks 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.
Chapter 1. Red Hat Cluster Suite Overview 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.
Conga 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. Only a system administrator is allowed to access this tab. •...
Chapter 1. Red Hat Cluster Suite Overview Figure 1.24. luci homebase Tab Figure 1.25. luci cluster Tab...
Cluster Administration GUI Figure 1.26. 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”...
Chapter 1. Red Hat Cluster Suite Overview 9.2.1. Cluster Configuration Tool You can access the Cluster Configuration Tool (Figure 1.27, “Cluster Configuration Tool”) through the Cluster Configuration tab in the Cluster Administration GUI. Figure 1.27. 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...
Cluster Administration GUI • 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.
Chapter 1. Red Hat Cluster Suite Overview Cluster Management tab in Cluster Administration GUI. Figure 1.28. Cluster Status Tool The nodes and services displayed in the Cluster Status Tool are determined by the cluster configuration file ( ). You can use the Cluster Status Tool to /etc/cluster/cluster.conf enable, disable, restart, or relocate a high-availability service.
Linux Virtual Server Administration GUI 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 — Cluster is a program for making online updates to the ccs_tool ccs_tool Cluster...
Chapter 1. Red Hat Cluster Suite Overview Web browser. You can access it locally with this URL: . You can http://localhost:3636 access it remotely with either the hostname or the real IP address followed by . If you are :3636 accessing the Piranha Configuration Tool remotely, you need an connection to the active LVS router as the root user.
GLOBAL SETTINGS Figure 1.30. 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.
Chapter 1. Red Hat Cluster Suite Overview 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 1.31. 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.
REDUNDANCY 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.
Chapter 1. Red Hat Cluster Suite Overview Figure 1.32. 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.
VIRTUAL SERVERS Figure 1.33. 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.
Chapter 1. Red Hat Cluster Suite Overview any of the subsections related to this virtual server, complete this page and click on the ACCEPT button. Figure 1.34. 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.
VIRTUAL SERVERS 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.
Chapter 1. Red Hat Cluster Suite Overview 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.
VIRTUAL SERVERS Figure 1.36. 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. Address The real server's IP address.
Chapter 1. Red Hat Cluster Suite Overview 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.
VIRTUAL SERVERS 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.
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.
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...
Cluster Components Function Components Description membership and services running. Daemon used to handle user service clurgmgrd requests including service start, service disable, service relocate, and service restart. Daemon used to handle Clustered clurmtabd NFS mount tables. Fence Fence agent for APC power switch. fence_apc Fence agent for for IBM Bladecenters fence_bladecenter...
Chapter 2. Red Hat Cluster Suite Component Summary Function Components Description environments. User interface for fence_ack_manual fence_manual agent. A program which performs I/O fencing fence_node on a single node. I/O Fencing agent for Xen virtual fence_xvm machines. I/O Fencing agent host for Xen virtual fence_xvmd machines.
Cluster Components Function Components Description A server daemon that allows a node gnbd_serv to export local storage over the network. This is the controlling process which pulse starts all other daemons related to LVS routers. At boot time, the daemon is started by the script.
Chapter 2. Red Hat Cluster Suite Component Summary Function Components Description monitoring daemon runs nanny nanny 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.
Man Pages • ccs (7) - Cluster Configuration System • cman_tool (8) - Cluster Management Tool • cluster.conf [cluster] (5) - The configuration file for cluster products • qdisk (5) - a disk-based quorum daemon for CMAN / Linux-Cluster • mkqdisk (8) - Cluster Quorum Disk Utility •...
Chapter 2. Red Hat Cluster Suite Component Summary • fence_xvm (8) - I/O Fencing agent for Xen virtual machines • fence_xvmd (8) - I/O Fencing agent host for Xen virtual machines • fenced (8) - the I/O Fencing daemon • High-availability Service Management •...
• 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/.