I see a lot problems with to small log disks. sizing exchange is a very imported thing!! Today there a lot of problems with Thiry-Party Devices. They can create a lot of log files if you run a oudated Exchange server. Transaction logs are truncated when backup software successfully backs up an Exchange server. The ‘Backup/Truncation Failure Tolerance' field in the Backup Configuration section, allows a value to be set that specifies how much capacity will be available for logs in the event of backup failures or issues with Thirth party devices. The default value is 3 days. change This!! This ensures that the server will continue to function and you have the ability to restore from transaction logs for x days, if the backup fails & and if some thirth party device give some trouble. Logs disk & backup should be monitored to ensure that they are successful.