Just as a quick side note. The Ubuntu server that this error relates to runs a webserver and a MySQL database with a big data load happening early in the morning and also drips through during the day. We have noticed that if the big data load happens when a backup is happening, the incremental backup can explode in size and it also blocks any new data loads until the backup has finished....as an example, a normal 6am backup is 20GB, if the dataload is still happening when this backup starts, it can block all data loads until the backup finishes and it can cause the backup size to go from 20GB to 50-100GB.