Greg Dodd diagnoses a problem:
I hit an error recently on a server that caused backups to fail. The database was backing up to a UNC path. Looking in the SQL Log file and Event Viewer, I found the following error:
The operating system returned the error ‘121(The semaphore timeout period has expired.)’ while attempting ‘DiskChangeFileSize’ on ‘\\uncpath\folder\databasename.bak’.
Read on to see what caused this error.