The voting disk records node membership information. A node must be able to access more than half of the voting disks at any time. To avoid simultaneous loss of multiple voting disks, each voting disk should be on a storage device that does not share any components (controller, interconnect, and so on) with the storage devices used for the other voting disks. If a node cannot access the minimum required number of voting disks it is evicted, or removed, from the cluster.
Thus proper management of voting disks can give great relief in times of disaster.
Given below are the most common tasks associated with Voting Disk management in an Oracle RAC environment.
1. Obtaining Voting disk Information
$ crsctl query css votedisk – gives a listing of all the in-use voting disks of you cluster.
2. Adding and Removing Voting Disks
To add or remove a voting disk, first shut down Oracle Clusterware on all nodes, then use the following commands as the root user, where path is the fully qualified path for the additional voting disk.
To add a voting disk: # crsctl add css votedisk path
To remove a voting disk: # crsctl delete css votedisk path
Caution: If you use the -force option to add or remove a voting disk while the Oracle Clusterware stack is active, you can corrupt your cluster configuration.
Note: If your cluster is down, then you can use the -force option to modify the voting disk configuration when using either of these commands without interacting with active Oracle Clusterware daemons.
3. Backing up Voting Disks
As a best practice it is recommended that you back up the voting disks at the following times:
· After installation
· After adding nodes to or deleting nodes from the cluster
· After performing voting disk add or delete operations
To make a backup copy of the voting disk, use the dd command. Perform this operation on every voting disk as needed where voting_disk_name is the name of the active voting disk and backup_file_name is the name of the file to which you want to back up the voting disk contents:
$ dd if=voting_disk_name of=backup_file_name
If your voting disk is stored on a raw device, use the device name in place of
voting_disk_name. For example:
$ dd if=/dev/sdd1 of=/tmp/vd1_
When you use the dd command for making backups of the voting disk, the backup can be performed while the Cluster Ready Services (CRS) process is active; you do not need to stop the crsd.bin process before taking a backup of the voting disk.
4. Recovering Voting Disks
If a voting disk is damaged, and no longer usable by Oracle Clusterware, you can recover the voting disk if you have a backup file. Run the following command to recover a voting disk where backup_file_name is the name of the voting disk backup file and voting_disk_name is the name of the active voting disk:
$ dd if=backup_file_name of=voting_disk_name
Needless to say, Keep your voting disk-backups safe.
