We are running backups using Symantec Backup Exec 11d. We have a 4TB iSCSI SAN drive. The backup media wizard is set to keep backups for two weeks. We currently have enough space to hold about a months worth of backups. The backup job has "Append to media, overwrite if no appendable media is available" selected. However, instead of overwriting old backups, backups seem to run until the drive is completely full and then stop mid-backup with the error "Low disk space." Why does this happen? Is there a way to fix this so that backups will overwrite old media correctly?