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Having determined what to back up and what backup storage media fits the best, you are to decide how the files will be processed. The main things to think about here are the method of backup and compression options.
Normally, file backup software doesn't back up your PC as a whole, but allows forming tasks involving variable sets of folders and files. For each backup task, for convenience in operation, the program creates a so-called index file which contains information about all data used in it. This file is then used for comparing current and old data when doing differential or incremental backups. Let's take a look at examples of different methods.
Full data backup
Full backup assumes that each time you execute the task, the entire set of data is copied to the chosen place. This type of backup takes the most disk space, time and PC resources, and often does a lot of senseless work (because unchanged, already backed up data becomes multiplied several times). On the other hand, for some types of data, e.g. when you create a complete disk image backup, full backup is the only effective option.
Incremental data backup
Incremental backup processes only files that appeared or changed since the previous backup. Say, you created a task for backing up My Documents folder. If you do an incremental backup immediately after a full backup, no files will be copied. But as soon as some files get modified, or new files are created, an incremental backup will process all modifications (which are calculated through comparing data in the index file with the current situation on the drive).
Incremental backups may be of two types: when files are rewritten in the same folder where the full backup is and when files are put into separate folders (which leads to creation of multiple instances of the same files). In Handy Backup, the latter option is called backup with timestamps.
Differential data backup
Differential backup is very much like incremental backup, with the only difference that it doesn't update the index file with each task execution, and therefore each task execution processes all modifications since the last full backup. This approach requires more disk space, as each differential backup is of the same size or larger than the previous one, but enables faster restoration of data, as compared to incremental backup.
Data compression options
Since backups are not meant to be used as separate documents, it's wise to enable automatic compression, in order to save storage space and transferring time (may be important if you back up online or back up to FTP). Here you need to decide, if you want to compress the backup set as a whole, or compress each individual file. The first variant gives the best results in terms of saving space, while the second one requires less PC resources and allows you to perform backups and restoration faster.
After choosing a backup type, it is important to choose how often backups will be performed - to choose a backup schedule.
The "Backup Tactics" series discusses different aspects of data backup and disaster recovery by giving real world examples from both home and enterprise environments. Alexander Rassokhin is an IT-expert and technical writer of Novosoft which is a developer of its own backup utility for Windows.
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