Personal Backup Version 5.2
	© 2012, J. Rathlev, IEAP, Kiel University

Alternating backup schedules

Basics

A professional backup normally uses alternating backups. To save time and disk space a full backup is not performed every day (or at any other interval). For example a full backup would only be run once a week with differential or incremental backups on other days. This means that only those files are saved that have changed since the last backup, the criterion being the state of the archive bit of each file. This bit will be set by the system automatically on writing the file. During a full backup, all archive bits of successfully backed-up files will be reset, hence it is possible to determine which files have been changed since the last backup. The differential and incremental methods differ in the following way:

Differential

All files with the archive bit set will be backed up. The archive bit will remain unchanged.

Incremental

All files with the archive bit set will be backed up. The archive bit will be reset.

This has the following effect when restoring files:

Alternating schedules using differential backups

First of all, the last differential backup is to be restored, followed by the last preceding full backup without overwriting any files.

Alternating schedules using incremental backups

First, all incremental backups are to be restored in reverse order without overwriting any files, followed by the last preceding full backup without overwriting any files.

Restoring is easier and faster with differential backups, but an incremental backup requires less disk space.

Alternating backups using the internal function of the program

For more details refer to Automatic backups.

Alternating backups using Windows Task Scheduler

Another way to start backups automatically is to use Windows Task Scheduler (more ..). This method has some advantages especially when implemented on a server (reduced usage of resources, runs with any user account). To create alternating backups with this function in a convenient way, I developed the utility program PbPlaner (see screenshot above). It is part of the distribution package of Personal Backup (see Windows start menu ⇒ All Programs ⇒ Personal Backup).

You can configure several alternating backups using this program. Their properties are displayed as a list. To edit a plan click on the appropriate line, make the required changes in the fields on the right and apply these by clicking the Replace button. Upon this, the selected plan will be reset to start.
To create a new plan, click New to clear all fields, make your desired settings and click Add to append the plan to the list.
To remove a plan from the list, select it and click Remove.

Settings:

Name: Save the plan to the list under this name.

Backup task: Click the button to select a backup task previously configured with Personal Backup, provided that it is not designated there as an automatic task. PbPlaner will then take over management of the alternating destination directories.

Number of cycles: Specify the number of cycles each consisting of one full and several differential or incremental backups.

Steps per cycle: Specify the number of backups within one cycle (including the full backup).
A cycle of 7 backups is a special case, in that the backups will be coupled to the days of the week.

Start on: When a cycle of 7 backups is selected, you can specify the day of the week on which the full backup is to be performed.

Full backup and ..: Select the differential or incremental backup mode for the additional backups within a cycle.

Create Windows scheduled task

Click this button (at the bottom left of the screenshot) to add the selected alternating schedule to Windows Task Scheduler (more ..). Click the adjacent Edit Windows scheduled task button to edit the settings of an existing scheduled task.

Important note

Changing an alternating schedule already designated as a scheduled task will directly affect the next backup.
Be careful when selecting the dates for your backups: they must match the settings for the alternating schedule. If you chose a cycle coupled to the days of the week (i.e. a cycle of 7 backups), the backup must start every day at a selectable time. All other modes allow any time interval to be chosen.

Step-by-step guide

The following guide will help the user understand how the program works.

Configure an alternating schedule

1. Click the New button: all settings will be reset to their initial values.
2. Insert a Name for the schedule under which it will be saved and displayed.
3. Enter a backup task previously configured with Personal Backup: clicking the button will open a dialog box for selecting the desired task.
4. Insert the number of full backups to be performed as Number of cycles: each cycle starts with a full backup followed by several differential or incremental backups. Each step is allotted its own subdirectory at the destination. After the last cycle, each subdirectory in turn will be overwritten.
5. The value n for Steps per cycle determines the number of backups within a cycle consisting of one full and n-1 differential or incremental backups.
6. If weekly cycles are selected (i.e. a cycle of 7 backups), the day for the full backup can be chosen. The cycle will then start (with its full backup) on the chosen day of the week as soon as this next occurs.
7. Finally, the new schedule must be added to the list using the Add button.

This completes the configuration of an alternating schedule. You can configure as many such schedules as you wish, but to implement these, each must be added as a Windows scheduled task.

Activate an alternating schedule

1. Select one of the preconfigured schedules by clicking on the list.
2. Click the Create Windows scheduled task button.
3. The wizard for configuring Windows scheduled tasks will open. All necessary Windows entries will be made by the program automatically.
4. If you wish, you can adjust the settings for Priority, Log and Subsequent action.
5. After clicking the Next button, the time schedule can be configured. Most required entries are self explanatory (details ...).
6. Another click on the Next button opens the dialog for specifying the name of the user whose credentials are to be used to start the backup. This must be an account with a valid password (details ...).
7. Clicking the Done button will activate the Windows scheduled task.

It is possible to edit the time schedule either by clicking the Edit Windows scheduled task button in PbPlaner or by using the Windows functions reached via All Programs ⇒ Accessories ⇒ System Tools ⇒ Task Scheduler or via Control Panel ⇒ Administrative Tools ⇒ Task Scheduler