Old backup sets for Windows 8 or Windows Server 2012 backup clients are removed from Kaseya, as per the "save last x backup sets" configuration in the schedule, but the files are not deleted from the image location.
Windows 8 and Windows Server 2012 operating systems are not supported by Kaseya Backup 4.0. The OS shell commands used by Kaseya Backup for deleting the older backup sets are no longer supported on Windows 8 or Server 2012.
Please refer to the system requirements page in the online help for details of supported operating systems -http://help.kaseya.com/WebHelp/EN/BUDR/4000000/index.asp#8102.htm
This is addressed in the next release of Kaseya Backup (v5.0) which is scheduled for release at the end of January 2014 and includes support for the latest operating systems.
Kaseya Backup (KBU) v4.0