Storage Foundation for Oracle® RAC 7.4.1 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
- How SF Oracle RAC works (high-level perspective)
- Component products and processes of SF Oracle RAC
- Periodic health evaluation of SF Oracle RAC clusters
- About Virtual Business Services
- About Veritas InfoScale Operations Manager
- About Veritas Services and Operations Readiness Tools (SORT)
- Administering SF Oracle RAC and its components
- Administering SF Oracle RAC
- Setting the environment variables for SF Oracle RAC
- Starting or stopping SF Oracle RAC on each node
- Applying Oracle patches on SF Oracle RAC nodes
- Migrating Pluggable Databases (PDB) between Container Databases (CDB)
- Installing Veritas Volume Manager, Veritas File System, or ODM patches on SF Oracle RAC nodes
- Applying operating system updates on SF Oracle RAC nodes
- Adding storage to an SF Oracle RAC cluster
- Recovering from storage failure
- Backing up and restoring Oracle database using Veritas NetBackup
- Enhancing the performance of SF Oracle RAC clusters
- Administering SmartIO
- Creating snapshots for offhost processing
- Managing database storage efficiently using SmartTier
- Optimizing database storage using Thin Provisioning and SmartMove
- Scheduling periodic health checks for your SF Oracle RAC cluster
- Using environment variables to start and stop VCSMM modules
- Verifying the nodes in an SF Oracle RAC cluster
- Administering VCS
- About managing VCS modules
- Viewing available Veritas device drivers
- Starting and stopping VCS
- Environment variables to start and stop VCS modules
- Adding and removing LLT links
- Configuring aggregated interfaces under LLT
- Displaying the cluster details and LLT version for LLT links
- Configuring destination-based load balancing for LLT
- Enabling and disabling intelligent resource monitoring for agents manually
- Administering the AMF kernel driver
- Administering I/O fencing
- About administering I/O fencing
- About the vxfentsthdw utility
- General guidelines for using the vxfentsthdw utility
- About the vxfentsthdw command options
- Testing the coordinator disk group using the -c option of vxfentsthdw
- Performing non-destructive testing on the disks using the -r option
- Testing the shared disks using the vxfentsthdw -m option
- Testing the shared disks listed in a file using the vxfentsthdw -f option
- Testing all the disks in a disk group using the vxfentsthdw -g option
- Testing a disk with existing keys
- About the vxfenadm utility
- About the vxfenclearpre utility
- About the vxfenswap utility
- Enabling or disabling the preferred fencing policy
- About I/O fencing log files
- Migrating from disk-based fencing to server-based fencing using the installer
- Migrating from server-based fencing to disk-based fencing using the installer
- Administering the CP server
- Administering CFS
- Administering CVM
- Listing all the CVM shared disks
- Establishing CVM cluster membership manually
- Changing the CVM master manually
- Importing a shared disk group manually
- Deporting a shared disk group manually
- Starting shared volumes manually
- Verifying if CVM is running in an SF Oracle RAC cluster
- Verifying CVM membership state
- Verifying the state of CVM shared disk groups
- Verifying the activation mode
- Administering Flexible Storage Sharing
- About Flexible Storage Sharing disk support
- About the volume layout for Flexible Storage Sharing disk groups
- Setting the host prefix
- Exporting a disk for Flexible Storage Sharing
- Setting the Flexible Storage Sharing attribute on a disk group
- Using the host disk class and allocating storage
- Administering mirrored volumes using vxassist
- Displaying exported disks and network shared disk groups
- Tuning LLT for memory and performance in FSS environments
- 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
- Restarting the installer after a failed network connection
- Installer cannot create UUID for the cluster
- Troubleshooting SF Oracle RAC pre-installation check failures
- Troubleshooting LLT health check warning messages
- Troubleshooting I/O fencing
- SCSI reservation errors during bootup
- The vxfentsthdw utility fails when SCSI TEST UNIT READY command fails
- Node is unable to join cluster while another node is being ejected
- System panics to prevent potential data corruption
- Cluster ID on the I/O fencing key of coordinator disk does not match the local cluster's ID
- Fencing startup reports preexisting split-brain
- Registered keys are lost on the coordinator disks
- Replacing defective disks when the cluster is offline
- Troubleshooting I/O fencing health check warning messages
- 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
- Restoring communication between host and disks after cable disconnection
- Shared disk group cannot be imported in SF Oracle RAC cluster
- Error importing shared disk groups in SF Oracle RAC cluster
- Unable to start CVM in SF Oracle RAC cluster
- CVM group is not online after adding a node to the SF Oracle RAC cluster
- CVMVolDg not online even though CVMCluster is online in SF Oracle RAC cluster
- Shared disks not visible in SF Oracle RAC cluster
- Troubleshooting CFS
- Troubleshooting interconnects
- Troubleshooting Oracle
- Error when starting an Oracle instance in SF Oracle RAC
- Clearing Oracle group faults
- Oracle log files show shutdown called even when not shutdown manually
- DBCA fails while creating an Oracle RAC database
- Oracle's clusterware processes fail to start
- Oracle Clusterware fails after restart
- Troubleshooting the Virtual IP (VIP) configuration in an SF Oracle RAC cluster
- Troubleshooting Oracle Clusterware health check warning messages in SF Oracle RAC clusters
- Troubleshooting ODM in SF Oracle RAC clusters
- Troubleshooting Flex ASM in SF Oracle RAC clusters
- Prevention and recovery strategies
- Tunable parameters
- Troubleshooting SF Oracle RAC
- Section III. Reference
Fencing startup reports preexisting split-brain
The vxfen driver functions to prevent an ejected node from rejoining the cluster after the failure of the private network links and before the private network links are repaired.
For example, suppose the cluster of system 1 and system 2 is functioning normally when the private network links are broken. Also suppose system 1 is the ejected system. When system 1 restarts before the private network links are restored, its membership configuration does not show system 2; however, when it attempts to register with the coordinator disks, it discovers system 2 is registered with them. Given this conflicting information about system 2, system 1 does not join the cluster and returns an error from vxfenconfig that resembles:
vxfenconfig: ERROR: There exists the potential for a preexisting split-brain. The coordinator disks list no nodes which are in the current membership. However, they also list nodes which are not in the current membership. I/O Fencing Disabled!
Also, the following information is displayed on the console:
<date> <system name> vxfen: WARNING: Potentially a preexisting <date> <system name> split-brain. <date> <system name> Dropping out of cluster. <date> <system name> Refer to user documentation for steps <date> <system name> required to clear preexisting split-brain. <date> <system name> <date> <system name> I/O Fencing DISABLED! <date> <system name> <date> <system name> gab: GAB:20032: Port b closed
However, the same error can occur when the private network links are working and both systems go down, system 1 restarts, and system 2 fails to come back up. From the view of the cluster from system 1, system 2 may still have the registrations on the coordination points.
Assume the following situations to understand preexisting split-brain in server-based fencing:
There are three CP servers acting as coordination points. One of the three CP servers then becomes inaccessible. While in this state, one client node leaves the cluster, whose registration cannot be removed from the inaccessible CP server. When the inaccessible CP server restarts, it has a stale registration from the node which left the SF Oracle RAC cluster. In this case, no new nodes can join the cluster. Each node that attempts to join the cluster gets a list of registrations from the CP server. One CP server includes an extra registration (of the node which left earlier). This makes the joiner node conclude that there exists a preexisting split-brain between the joiner node and the node which is represented by the stale registration.
All the client nodes have crashed simultaneously, due to which fencing keys are not cleared from the CP servers. Consequently, when the nodes restart, the vxfen configuration fails reporting preexisting split brain.
These situations are similar to that of preexisting split-brain with coordinator disks, where you can solve the problem running the vxfenclearpre command. A similar solution is required in server-based fencing using the cpsadm command.