allsorts
You seem to misunderstand.
The backup is done to a Windows workstation share.
The backup file is then burnt to a CD using the CD burner on the Windows workstation.
Restore of files larger than 2GB is not supported due to Apache limitations, so the only reliable way to restore the backup file is via a CD.
The CD is then inserted into the drive in the sme server.
When you first install the sme operating system software and the server reboots for the first time, you are presented with an option to allow you to restore from CD.
You then restore from the backup file on the CD.
All of the above has nothing to do with burning CD or DVD backups directly on the server as that is not currently supported.
The above method would not usually be used for doing regular routine daily backups.
For routine backups you could use the backup dar contrib or the e-smith backup with dar contrib (under test for inclusion into the base release), but neither of these burn directly to CD's. They save to a share on a workstation, which could be a removable (IDE, SATA or USB) hard drive, or to a USB drive mounted directly on the server.
I'm not aware of any current contrib for sme 7.2 or 7.3 that burns backups directly to CD's or DVD's although there have been suggestions and methods outlined for previous versions of sme server.