Difference between revisions of "CentOS Cluster Configuration"
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====active-passive example==== | ====active-passive example==== | ||
Two ''front-end-nodes'' have the responsibility of delivering a high-availability WEB-service. In the image below there are three services | Two ''front-end-nodes'' have the responsibility of delivering a high-availability WEB-service. In the image below there are three services | ||
| + | {| | ||
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| + | |valign="top"| | ||
#Filesystem: The filesystem is a [[ext3]] filesystem which can only be mounted on one node at a time. In Picture 1 below the left node has mounted the shared filesystem on the SCSI-raid controllers. The other servers has not mounted the shared filesystem. | #Filesystem: The filesystem is a [[ext3]] filesystem which can only be mounted on one node at a time. In Picture 1 below the left node has mounted the shared filesystem on the SCSI-raid controllers. The other servers has not mounted the shared filesystem. | ||
#Service: The Apache WEB-server service is running on the left node, and using the resources from the shared SCSI filesystem delivering WEB-content to the Internet. The Apache service on the other nodes are stopped. | #Service: The Apache WEB-server service is running on the left node, and using the resources from the shared SCSI filesystem delivering WEB-content to the Internet. The Apache service on the other nodes are stopped. | ||
#IP address: The left server is answering request for the shared IP address 80.1.2.3. The other nodes ignores 80.1.2.3. | #IP address: The left server is answering request for the shared IP address 80.1.2.3. The other nodes ignores 80.1.2.3. | ||
| − | [[Image:Cluster active-passive.png| | + | |valign="top"| |
| + | |[[Image:Cluster active-passive.png|200px|thumb|Picture 1: Active-passive example]] | ||
| + | |[[Image:Cluster active-passive fail.png|200px|thumb|Picture 2: Active failed example]] | ||
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| + | |} | ||
== files and programs== | == files and programs== | ||
Revision as of 09:23, 5 April 2009
Contents
cluster.conf configuration file
Configuration file for:
- cman - Cluster configuration
- fence - Fence configuration for disabling nodes with errors
- dlm - Distributed Lock Manager Configuration. Rules for access to shared resources
- gfs - Global file System configuration. Shared file systems among nodes.
- rgmanager - Resource Group manager configuration. Fx. apache service setup on cluster.
cman - Basci cluster config
fence - Fencing nodes
dlm - lock management
gfs - global file system
rgmanager - resource config
Resource Group manager is a High Availability service. Rgmanager can start and stop services on nodes. If a service is failing on one node it will be started on another node. Rgmanager monitor the services and make sure they are actually runnning.
Service Groups
A Service Group is a group of nodes on which a specified service can be started or stopped by rgmanager. Not all nodes in a cluster need to be member of a Service Group. There can be many Service Groups in a cluster.If a service fails, a script is called to automatically restart the service. If a node fails, the service may be relocated to a different node in the service group.
What is a Cluster-service
A Cluster-service is a resource that are shared among nodes. For example a apache WEB-service. This service can be run in two different ways.
active-passive Cluster-service
An active-passive Cluster-service is a service running on one node at a time. If the node running the service fails the service is started on another node in the Service Group.
active-passive example
Two front-end-nodes have the responsibility of delivering a high-availability WEB-service. In the image below there are three services
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files and programs
- /usr/share/cluster - here lives the rgmanager scripts
- /etc/cluster/cluster.conf - rgmanager configuration
- clustat - See cluster and service status clustat -s SERVICE_NAME -l
- RedHAT rgmanager FAQ