Scheduling Backups

• Plan full and partial backups to efficiently duplicate the most recent system information.

• Schedule a regular time for performing backups.

Full and Partial Backups

There are two ways to perform a system backup. A full backup copies all files stored in your system whether or not any of the information in them has changed since the last backup. A partial, or incremental, backup copies only the files that have changed since the last full backup. This can be done with the DATE parameter of the STORE command. A well-planned backup schedule combines both methods. It usually calls for a full backup once a week and a partial backup each remaining workday. If you follow such a schedule, you would lose no more than 24 hours worth of information should the system experience problems.

Your requirements for recovery time should also be considered. Although it takes less time to make partial backups of your data between full backups, it also takes longer to restore them, should you need to. When restoring from partial backups, the last complete full backup must be restored first. Then, each subsequent partial backup must be restored. This is in contrast to spending more time each night on a full backup, but only needing to restore files once. You should examine your recovery time needs and expectations before deciding on a backup strategy.

Figure 2-1 “Sample Backup” shows a sample backup schedule that combines both full and partial system backups.

Figure 2-1 Sample Backup

Selecting a Time for Backups

It is best to perform backups at a time when people are not normally using the system. Often, system administrators choose to perform backups at the close of the workday or later in the evening. It is also a good idea to schedule the backup for the same time every day so users know when to expect it and can plan ahead.

Be sure to schedule enough time for each backup. Full backups take more time and more media than partial backups. Performing a partial backup a day or so after a full backup takes less time and less backup media than a partial backup performed almost a week later.

As the week progresses, users will have modified or added more files since the last full backup, and more new information must be duplicated. If you perform a full backup on Friday, the first partial backup on Monday may take only one tape, for example, and not much time. By Thursday, however, the day before the next scheduled full backup, a partial backup requires several tapes, for example, and considerably more time, but still less than a full backup.

The TurboSTORE/iX 7x24 True-Online Backup ONLINE option allows you to back up critical data and applications that need to be available at all times. Using just the ONLINE option allows users to access files after a short period of inaccessibility at the beginning of the backup. However, using the new ONLINE=START or ONLINE=END options, users can continue to access files, uninterrupted, throughout the backup.

Refer to Chapter 6, "STORE and TurboSTORE Command Options," for information on using the ONLINE option only, or Chapter 7, "TurboSTORE/iX 7x24 True-Online Backup," for information on using the new ONLINE=START and ONLINE=END options.