Backing up your existing file systems before you upgrade to the Solaris OS is highly recommended. If you copy file systems to removable media, such as tape, you can safeguard against data loss, damage, or corruption.
For detailed instructions to back up your system, refer to Chapter 23, Backing Up and Restoring UFS File Systems (Overview), in System Administration Guide: Devices and File Systems.
To backup your system when non-global zones are installed, see Chapter 26, Solaris Zones Administration (Overview), in System Administration Guide: Solaris Containers-Resource Management and Solaris Zones.
In previous releases, the restart mechanism enabled you to continue an upgrade after a loss of power or other similar problem. Starting with the Solaris 10 10/08 release, the restart mechanism is unreliable. If you have a problem, your upgrade might not restart.