Using the snapshot function by proxy volumes, another boot environment (alternative boot environment) can be created without influencing the current boot environment during system operation. System stop time at the time of backup and restoration work for system volumes (/, /usr, /var, swap area) can be reduced drastically by using the alternative boot environment. In addition, system and service stop time when modifying the system such as reconfiguring system volumes and applying patches can also be reduced.
In a SAN environment with ETERNUS Disk storage system, it is possible to create an alternative boot environment using the Advanced Copy function without imposing loads on the server.
Note
An alternative boot environment cannot be created in a ZFS boot environment.
An alternative boot environment can be created with the GDS Snapshot command following the procedure as below.
Creating snapshots of system volumes
Create snapshots of system volumes in the current boot environment using proxy volumes. Snapshots can be created during system operation.
Configuring an alternative boot environment
Make booting available through snapshot volumes (proxy volumes) instead of system volumes in the current boot environment. This configuration changes the /etc/vfstab files and the /etc/system files copied from the root volume (/) to the proxy volumes when snapshots were created. The current boot environment is not changed.
The environment can be switched to the alternative boot environment by simply specifying the name of a boot device name in the alternative boot environment and rebooting the system. The original boot environment can be restored by simply specifying the name of a boot device in the original boot environment and rebooting the system.
Using an alternative boot environment can reduce system and service stop time when performing maintenance work and reconfiguration work for the system as follows.
Backing up the system
An alternative boot environment can be assumed as a backup of the system. Since an alternative boot environment can be created during system operation, stopping the system is no longer necessary at the time of backup work.
Restoring when the system fails
When booting the system becomes unavailable due to a system disk failure or data crash, the system operation can be resumed by switching to an alternative boot environment. In addition, data on original system volumes can be restored from data in an alternative boot environment during system operation in the alternative boot environment, and the original boot environment can be switched back to by simply rebooting the system.
Reconfiguring the system
The disk configuration of system volumes can be changed by creating an alternative boot environment and switching to the alternative boot environment. In addition, expanding the capacity and applying patches for volumes used in the alternative boot environment are available during system operation. These operations can be performed during system operation, and have no effect on the current boot environment. If booting an alternative boot environment fails or the performance of an alternative boot environment is improper, the current boot environment can be switched back to by simply rebooting the system.
See
For examples of using an alternative boot environment, see "6.4 Backing Up and Restoring a System Disk through an Alternative Boot Environment" and "D.20 Volume Expansion Using Commands."
