•Cluster nodes should be running the same HACMP maintenance levels. There might be incompatibilities between various maintenance levels of HACMP, so you must ensure that consistent levels are maintained across all cluster nodes. The cluster must be taken down to update the maintenance levels.
8.7Backup Strategies
HACMP software masks hardware failures in clustered RISC System/6000 environments by quickly switching over to backup machines or other redundant components. However, installing HACMP is not a substitute for having a formal backup and recovery procedure.
In general, a backup of user and system data is kept in case data is accidentally removed or in case of a disk failure. A formal backup process is really an insurance policy. You invest in the technology and time to back up systems so that, in the event of a problem, you can quickly rebuild the system.
Since system and application backups are preferably done during periods of no usage (for instance, in the middle of the night), many installations implement an automated backup procedure using the AIX cron facility. While this is a very good procedure, the HACMP cluster environment presents some special challenges. The problem is, you never know which machine has your application data online, so you need to ensure that exactly the node that has a resource online will initiate the backup of data.
It isn’t actually important which of the several backup commands you are using, what is important is the strategy. For the features and/or restrictions of backup commands like tar, cpio, dd or backup, refer to the AIX Commands Reference Version 4.3,
8.7.1 Split-Mirror Backups
No file system can be safely backed up while update activity is occurring. If you are going to have any assurance as to which updates are on the backup and which updates are not, you need to be able to demark exactly where the backup was made. Therefore, it may be difficult to do a good backup on systems that have applications or data that must be online continuously or offline for only a very short time. In some installations, the time required to do a full backup to an archival device, or even to another, might be longer than the availability requirements of the application will allow it to be offline. The mirroring capability of the AIX Logical Volume Manager (LVM) can be used to address this issue.
