The log save locations move around depending on what stage of the OS build we are looking at. This is a breakdown of the log locations during a MDT install task sequence:
1. Before the Image is applied to the machine:
X:\MININT\SMSOSD\OSDLOGS
2. After the system drive has been formatted:
C:\MININT\SMSOSD\OSDLOGS
3. After Deployment:
%WINDIR%\TEMP\DeploymentLogs
The logs of most interest for troubleshooting a failed install will be:
BDD.LOG – This is an aggregated log of all the MDT Logs.
SMSTS.LOG – This log would be used to troubleshoot Task Sequence errors.
Also note that each MDT ZTI script creates its own log files during execution (example: ZTIGather.log, ZTIDiskpart.log, ZTIDrivers.log, etc)
VIDEO : https://keithga.wordpress.com/2014/10/24/video-mdt-2013-log-files-basics-bdd-log-and-smsts-log/