Skype for business server fabric traces are enabled by default. You can find the fabric traces in following location; C:\ProgramData\Windows Fabric\Log\Traces. There is a possibility, some strange fabric issues can fill up your system drive space. Following article may help you to reduce the fabric traces to one day.
Take a backup of the 'ClusterManifest.Xml.Template' file from following location ;C:\Program Files\Skype for Business Server 2015\Server\Core.
Open the ClusterManifest.Xml.Template file in notepad and change the 'DataDeletionAgeInDay' parameter under local winFabEtlFile section to 1 and save the file.
Repeat the same steps on all FE servers in the skype for business pool. Restart the servers one by one, whichever FE server comes online first will generate the manifest from this file and will be distributed throughout the cluster. Please note, fabric update/CU update may overwrite the ClusterManifest.Xml.Template file. You need to modify the files once changes are completed. Now fabric traces will be overwritten on each day.