CentOS Cluster Configuration - Revision history

Heth at 12:32, 8 November 2009

2009-11-08T12:32:36Z

Heth: /* cman - Basci cluster config */

2009-05-04T12:50:00Z

‎cman - Basci cluster config

Heth: /* active-active example */

2009-04-07T05:21:30Z

‎active-active example

Heth: /* active-active example */

2009-04-07T05:06:25Z

‎active-active example

Heth at 05:23, 6 April 2009

2009-04-06T05:23:10Z

Heth: /* What is a Cluster-service */

2009-04-05T10:51:37Z

‎What is a Cluster-service

Heth: /* rgmanager - resource config */

2009-04-05T10:39:03Z

‎rgmanager - resource config

Heth: /* active-passive example */

2009-04-05T10:24:44Z

‎active-passive example

Heth: /* active-passive example */

2009-04-05T08:23:58Z

‎active-passive example

Heth: /* active-passive example */

2009-04-05T08:06:53Z

‎active-passive example

@@ Line 70: / Line 70: @@
 *''clustat'' - See cluster and service status ''clustat -s SERVICE_NAME -l''
 *[http://sources.redhat.com/cluster/wiki/FAQ/RGManager RedHAT rgmanager FAQ]
-[[category:linux]][[category:cluster]]
+[[category:linux]][[category:cluster]][[Category:CentOS]]

@@ Line 9: / Line 9: @@
 *rgmanager - Resource Group manager configuration. Fx. apache service setup on cluster.
 See [http://sources.redhat.com/cluster/doc/cluster_schema_rhel5.html RedHAT 5 cluster scheme]
-=cman - Basci cluster config=
+=cman - Basic cluster config=
 =fence - Fencing nodes=
 =dlm - lock management=

@@ Line 47: / Line 47: @@
 An ''active-active'' Cluster-service is a service running on all the nodes at the same time. If a node fails the other nodes takes over the load.
 ====active-active example====
-Three ''front-end-nodes'' have the responsibility of delivering a high-availability and high-load WEB-service. In the image below there are three services
+Three ''front-end-nodes'' have the responsibility of delivering a high-availability and high-load WEB-service.
 {|
 |-
 |valign="top"|
-===== Picture 1 - Normal operation =====
+===== Picture 3 - Normal operation =====
-#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 [[GFS]] filesystem which can be mounted on several nodes on the same time. In Picture 3 WEB requests from the Internet to 80.1.2.3 are distributed to the WEB-server nodes 10.2.2.1, 10.2.2.2 and 10.2.2.3 in a ''Round Robin'' fashion by the ''Load Balancer'' so each server is serving 1/3 of the requests. Of course the ''Load balancer'' should be redundant.
-#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.
+===== Picture 4 - Fault in left node =====
-#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.
+When an error is discovered the failing node should be fenced, and
-===== Picture 2 - Fault in left node =====
+*Either the ''Load Balancer'' should stop sending requests to 10.2.2.1 or
-When an error is discovered by the ''rgmanager'' on the failing node, ''rgmanager'' communicates with the ''rgmanager'' on the other nodes and decide which other node should transition from ''passive'' to ''active''. In the example on Picture 2, the middle node goes to active and continues to server WEB-requests to 80.1.2.3.
+*One of the other nodes should start also serving requests for 10.2.2.1
 |valign="top"|

@@ Line 64: / Line 64: @@
 |valign="top"|
-|[[Image:Cluster active-passive.png|200px|thumb|Picture 1: Active-passive example]]
+|[[Image:Cluster active-active.png|200px|thumb|Picture 3: Active-Active example]]
-|[[Image:Cluster active-passive fail.png|200px|thumb|Picture 2: Active failed example]]
+|[[Image:Cluster active-active fail.png|200px|thumb|Picture 4: A Active failed example]]
 |-
 |}

@@ Line 1: / Line 1: @@
 =cluster.conf configuration file=
 Configuration file for:
@@ Line 72: / Line 74: @@
 *''clustat'' - See cluster and service status ''clustat -s SERVICE_NAME -l''
 *[http://sources.redhat.com/cluster/wiki/FAQ/RGManager RedHAT rgmanager FAQ]

@@ Line 19: / Line 19: @@
 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.
+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
+Three ''front-end-nodes'' have the responsibility of delivering a high-availability WEB-service. In the image below there are three services
 {|
 |-

@@ Line 12: / Line 12: @@
 =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.
+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.<br/>
 == 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.
@@ Line 31: / Line 32: @@
 When an error is discovered by the ''rgmanager'' on the failing node, ''rgmanager'' communicates with the ''rgmanager'' on the other nodes and decide which other node should transition from ''passive'' to ''active''. In the example on Picture 2, the middle node goes to active and continues to server WEB-requests to 80.1.2.3.
 ====== Transition steps in example ======
 |valign="top"|
 |[[Image:Cluster active-passive.png|200px|thumb|Picture 1: Active-passive example]]