SharePoint 2010 - Could not allocate space for object

The day was going along great when all of a sudden a lot of users were experiencing problems with our SharePoint site. I checked the SharePoint log file using the ULS viewer and with the correlation id from one of the errors I found this entry:

System.Data.SqlClient.SqlException: Could not allocate space for object 'dbo.AllUserData'.'AllUserData_ParentId' in database 'Insite_Content' because the 'PRIMARY' filegroup is full. Create disk space by deleting unneeded files, dropping objects in the filegroup, adding additional files to the filegroup, or setting autogrowth on for existing files in the filegroup. at System.Data.SqlClient.SqlConnection.OnError(SqlException exception, Boolean breakConnection) at System.Data.SqlClient.TdsParser.ThrowExceptionAndWarning(TdsParserStateObject stateObj) at System.Data.SqlClient.TdsParser.Run(RunBehavior runBehavior, SqlCommand cmdHandler, SqlDataReader dataStream, BulkCopySimpleResultSet bulkCopyHandler, TdsParserStateObject stateObj) at System.Data.SqlClient.SqlDataReader.HasMoreRows() at System.Data.SqlClient.SqlDataReader.ReadInternal(Boolean setTimeout) at System.Data.SqlClient.SqlDataReader.NextResult() at Microsoft.SharePoint.SPSqlClient.ExecuteQueryInternal(Boolean retryfordeadlock) at Microsoft.SharePoint.SPSqlClient.ExecuteQuery(Boolean retryfordeadlock)

Turns out our SQL server is configured to do a daily backup to the same drive as the SQL database files and the drive was full after three months of backups. Isn't that just brilliant! There was no room for the database to grow. I removed some of the old backup files to free up some space and things were back to normal. Just to make sure this problem didn't happen again before we found the time to make this right, I added a cleanup task onto the backup maitenance job so that backup files older then 4 weeks would be deleted.