Windows Server doesn't automatically clean any of its web log files, and can grow to 100+ GB in size.
 While it is possible to use health monitor or other monitoring toools to keep an eye on disk space you do not want your backups or apps failing due to a log file being too large.

Advice in this thread here helps with defining a sheduled command that will keep a handle on the log files.
 
Setup the task scheduler using the following command:
 
at 12:00 /EVERY:Su Forfiles.exe -p C:\WINDOWS\system32\LogFiles\W3SVC1 -m *.log -d -30 -c \"Cmd.exe /C del @path\" 
 
Adjust the paths and the schedule to fit your needs.
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