Weekend and Nightly Backups

There are three basic types of weekend and nightly backups:

1. Full backups – all primary storage data is written to a set of tapes. If a full backup is performed on 10TB of primary data, all 10TB will be written to a set of ten tapes every weekend. Full backups are typically run for all data on all servers during the weekend. In addition, certain applications like databases and email data stores might also be backed up nightly as a full backup. Since the full backup process consumes a tremendous amount of network bandwidth and client system processing and storage cycles, full backups are typically performed on the weekend to minimize the performance impact on users and applications.

2. Differential backups – all primary storage data that has changed since the last full backup are written to a set of tapes. If a full backup was completed on a Saturday night, a Wednesday night differential backup would protect all of the files that were created and changed on Sunday, Monday, Tuesday and Wednesday. If differential backups were run every night, the size of backups and the time to perform backups would become too great, so typically, differentials are run once or twice in the middle of the week. The advantage of running a differential backup is reduced time to restore files later in the week.

3. Incremental backups – all primary storage data that has changed since the last incremental backup are written to a set of tapes. With an incremental backup, since only changed files are backed up, the time and burden on server and network resources is kept to a minimum. The trade off of using a weekend full / daily incremental approach is that if system or data loss occurs mid-week, the full backup has to be restored first, and then each incremental backup has to be restored in successive order. If a failure occurred on Thursday, first the data from the last full weekend backup would be restored, followed by sequential restores from Monday, Tuesday and Wednesday night’s incremental backups, which can significantly extend the time it takes to restore data.

For each type of data in an organization, different backup policies may be in effect. Here are some examples:

Weekend and nightly backups are used to restore files that have been accidentally deleted or have become corrupted. Most organizations maintain between four weeks and 26 weeks of full backups and the last one to four weeks of incremental / differential backup data on site. This allows users to request the restoration of data from an earlier copy.

Historical data in the form of weekly and nightly backups may be required by financial staff when third party auditors request financial information as of a certain date. Lawyers, in response to legal inquiry or subpoena may be required to produce these files from historical backup tapes.

Weekend and nightly backups typically require a duplicate tape be created to keep a complete data set of all primary data off site in case of a site disaster such as pipes bursting, natural flooding, hurricanes, tornadoes, fires and other disasters.

A backup server is a standard server that has backup software loaded onto it. Backup servers are connected to a local disk subsystem and/or one or more tape drives within tape libraries.  Backup servers also communicate with servers, desktops and laptops to be backed up by having backup client (agent) software loaded onto each system. The backup agent moves all data with that server over the network to a backup server. Since the backup process consumes client machine processing and storage cycles, backups are typically performed at night to minimize the performance impact on users and applications.

Disk-based Storage for Weekend and Nightly Backups

Due to the complexity of managing tens to hundreds of tapes created by weekend and nightly backups, and the challenges of quick and reliable data restores from these tapes, most companies are moving to disk-based backup at their primary site while maintaining tape for offsite data protection. This combination provides faster, more reliable and more manageable local disk-based backups and restores of data while keeping the cost of storing data offsite on tapes at a minimum.