EMC DL3D 1500 Administrator's Manual page 111

b. From the list box, select the end time for the backup window.
Note: If de-duplication does not complete before the next backup
window occurs, de-duplication of the previous day's backup data will
continue until finished. This can cause your backup window to extend.
De-duplication of the current backup will not occur until the backup
window expires.
5. Click Apply.
Adding an OST storage server
Figure 14
Configuring and Managing Disk Backup
Configuring and managing OST 111