Acronis True Image Home 2012 cannot split already existing backups. Backups can be split only when being created.
Large backups can be split into several files that together make up the original backup. A backup can also be split for burning to removable media.
The default setting - Automatic. With this setting, Acronis True Image Home 2012 will act as follows.
When backing up to a hard disk:
When backing up to a CD-R/RW, DVD-R/RW, DVD+R/RW, BD-R/RE:
Alternatively, you may select the desired file size from the drop-down list. The backup will then be split into multiple files of the specified size. That comes in handy when backing up to a hard disk with the view to burning the backup to CD-R/RW, DVD-R/RW, DVD+R/RW or BD-R/RE later on.
Creating images directly on CD-R/RW, DVD-R/RW, DVD+R/RW, BD-R/RE might take considerably more time than it would on a hard disk.