Backups are an essential part of a service supporting any organization. Unusually, an email server has little data that changes, apart from the various spools of email currently being processed. The content of these spools changes very quickly, and so the data is difficult to back up. As a result, a daily backup is superfluous, but the whole machine configuration should be backed up whenever it is modified to aid recovery after hardware failure. Hardware RAID or software RAID can be used to guard against disk failures.