I wanted to upgrade my SLES 11 SP4 Installation to SLES 12 SP4. During the Upgrade iam getting the following Error Message:

Internal error. Please report a bug report with logs.
Run save_y2logs to get complete logs.
Details: Filesystem snapshot could not be created
Caller: /usr/share/YaST2/lib/yast2/fs_snapshot.rb:201:in 'create'

What could be the issue?