Storage Foundation for Oracle® RAC 7.3.1 Administrator's Guide - Linux
- Section I. SF Oracle RAC concepts and administration
- Overview of Storage Foundation for Oracle RAC
- About Storage Foundation for Oracle RAC
- Component products and processes of SF Oracle RAC
- About Virtual Business Services
- Administering SF Oracle RAC and its components
- Administering SF Oracle RAC
- Starting or stopping SF Oracle RAC on each node
- Administering VCS
- Administering I/O fencing
- About the vxfentsthdw utility
- Testing the coordinator disk group using the -c option of vxfentsthdw
- About the vxfenadm utility
- About the vxfenclearpre utility
- About the vxfenswap utility
- Administering the CP server
- Administering CFS
- Administering CVM
- Changing the CVM master manually
- Administering Flexible Storage Sharing
- Backing up and restoring disk group configuration data
- Administering SF Oracle RAC global clusters
- Administering SF Oracle RAC
- Overview of Storage Foundation for Oracle RAC
- Section II. Performance and troubleshooting
- Troubleshooting SF Oracle RAC
- About troubleshooting SF Oracle RAC
- Troubleshooting I/O fencing
- Fencing startup reports preexisting split-brain
- Troubleshooting CP server
- Troubleshooting server-based fencing on the SF Oracle RAC cluster nodes
- Issues during online migration of coordination points
- Troubleshooting Cluster Volume Manager in SF Oracle RAC clusters
- Troubleshooting CFS
- Troubleshooting interconnects
- Troubleshooting Oracle
- Troubleshooting ODM in SF Oracle RAC clusters
- Prevention and recovery strategies
- Tunable parameters
- Troubleshooting SF Oracle RAC
- Section III. Reference
CVM architecture
CVM is designed with a "master and slave" architecture. One node in the cluster acts as the configuration master for logical volume management, and all other nodes are slaves. Any node can take over as master if the existing master fails. The CVM master exists on a per-cluster basis and uses GAB and LLT to transport its configuration data.
Just as with VxVM, the Volume Manager configuration daemon, vxconfigd, maintains the configuration of logical volumes. This daemon handles changes to the volumes by updating the operating system at the kernel level. For example, if a mirror of a volume fails, the mirror detaches from the volume and vxconfigd determines the proper course of action, updates the new volume layout, and informs the kernel of a new volume layout. CVM extends this behavior across multiple nodes and propagates volume changes to the master vxconfigd.
Note:
You must perform operator-initiated changes on the master node.
The vxconfigd process on the master pushes these changes out to slave vxconfigd processes, each of which updates the local kernel. The kernel module for CVM is kmsg.
See Figure: Low-level communication.
CVM does not impose any write locking between nodes. Each node is free to update any area of the storage. All data integrity is the responsibility of the upper application. From an application perspective, standalone systems access logical volumes in the same way as CVM systems.
By default, CVM imposes a "Uniform Shared Storage" model. All nodes must connect to the same disk sets for a given disk group. Any node unable to detect the entire set of physical disks for a given disk group cannot import the group. If a node loses contact with a specific disk, CVM excludes the node from participating in the use of that disk.
Set the storage_connectivity tunable to asymmetric to enable a cluster node to join even if the node does not have access to all of the shared storage. Similarly, a node can import a shared disk group even if there is a local failure to the storage.
For detailed information, see the Storage Foundation Cluster File System High Availability Administrator's Guide.