Acronis Backup for Linux Server - User Guide - Manual (Page 24)

24 Copyright © Acronis International GmbH, 2002-2014
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you need the possibility to roll back to any one of multiple saved states
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the data changes tend to be small as compared to the total data size.
It is widely accepted that incremental backups are less reliable than full ones because if one backup
in the "chain" is corrupted, the next ones can no longer be used. However, storing multiple full
backups is not an option when you need multiple prior versions of your data, because reliability of an
oversized archive is even more questionable.
Example: Backing up a database transaction log.
Differential backup
A differential backup stores changes to the data against the latest full backup. You need access to
the corresponding full backup to recover the data from a differential backup. A differential backup is
most useful when:

you are interested in saving only the most recent data state

the data changes tend to be small as compared to the total data size.
The typical conclusion is: "differential backups take longer to do and are faster to restore, while
incremental ones are quicker to do and take longer to restore." In fact, there is no physical difference
between an incremental backup appended to a full backup and a differential backup appended to
the same full backup at the same point of time. The above mentioned difference implies creating a
differential backup after (or instead of) creating multiple incremental backups.
An incremental or differential backup created after disk defragmentation might be considerably larger than
usual because defragmentation changes file locations on the disk and the backup reflects these changes. It is
recommended that you re-create a full backup after disk defragmentation.
The following table summarizes the advantages and shortcomings of each backup type as they
appear based on common knowledge. In real life, these parameters depend on numerous factors
such as the amount, speed and pattern of data changes; the nature of the data, the physical
specifications of the devices, the backup/recovery options you set, to name a few. Practice is the
best guide to selecting the optimal backup scheme.
Parameter Full backup Differential backup Incremental backup
Storage space
Maximal Medium Minimal
Creation time
Maximal Medium Minimal
Recovery time
Minimal Medium Maximal
3.5 What does a disk or volume backup store?
A disk or volume backup stores a disk or a volume file system as a whole and includes all of the
information necessary for the operating system to boot. It is possible to recover disks or volumes as a
whole from such backups as well as individual folders or files.
Windows
A volume backup stores all files and folders of the selected volume independent of their
attributes (including hidden and system files), the boot record, the file allocation table (FAT) if it
exists, the root and the zero track of the hard disk with the master boot record (MBR).
A disk backup stores all volumes of the selected disk (including hidden volumes such as the
vendor's maintenance partitions) and the zero track with the master boot record.
The following items are not included in a disk or volume backup (as well as in a file-level backup):