Marking Volume Groups for use in Service guard

Marking a Volume Group for Serviceguard

·         Marking Volume Groups for Serviceguard                     # vgchange –c y VGName

·         Marking Volume Groups as non-Serviceguard               # vgchagne –c n VGName

The vgchange –c y VGName command marks a volume groups as part of a cluster. The vgchange –a n VGName command removes an existing mark, indicating that the volume group is no longer part of a cluster. These options are applied automatically by the cmapplyconf command when the volume group is listed in the cluster-wide ASCII file

Volume Group Activation Modes

·         Standard Volume Groups Activation                              # vgchange –a y VGName

·         Standard Volume Groups Deactiviation                          # vgchange –a n VGName

·         Exclusive Volume Group Activation                                 # vgchange –a e VGName

·         Exclusive Volume Group Deactivation                             # vgchange –a n VGName

·         Shared mode activation                                                 # vgchange –a s VGName

The vgchange -a y VGName command activates a volume group for standard read/write access.

When activated in standard read/write mode, both nodes can write to the file system concurrently. This is standard LVM functionality. This mode of activation is not supported for Serviceguard volume groups. This mode of activation can only be used on non-marked volume groups.

The vgchange -a e VGName command activates a volume group for exclusive read/write access.

When a node activates a volume group in exclusive read/write mode, the node will be the only node to have write access to the volume group. This mode of activation only works if no other node in the cluster has already activated the volume group. This mode of activation is the only supported activation mode for Serviceguard marked volume groups.

There is a method of activating a volume group in shared mode. The vgchange –a s VGName command is used with Shared Logical Volume Manager where the logical volumes are being accessed concurrently by multiple nodes and the application is managing the concurrency and synchronization of data on the disk. This is used by Oracle Real Time Application Clusters (RAC) using SLVM. Newer implementations of Oracle RAC are now using CFS.