What is split-volume backup?

Split-volume or online backup uses mirrored disks to perform file backup while allowing users to continue accessing those same files. A mirrored volume set is "split" into two identical sets of data. One of the sets is used for normal access and operation, while the other is used exclusively for backup. When the backup is complete, the backup volumes are overwritten with the contents of the user volumes (which may have undergone modifications). Normal disk mirroring resumes after this point. Refer to Figure 1-2 “Split-Volume Backup”.

The volume set is continuously available except during the time it takes to close the volume set, split it, and open it. Only mirrored volume sets may be backed up using this method.

Figure 1-2 Split-Volume Backup