User`s guide

• When performing incremental backups of data that does not change itself, but changes its

location. Such is the case when multiple pieces of data circulate over the network or within one

system. Each time a piece of data moves, it is included in the incremental backup which becomes

sizeable while it does not contain new data. Deduplication helps to solve the problem: each time

an item appears in a new place, a reference to the item is saved instead of the item itself.

Deduplication and incremental backups

In case of random changes to the data, de-duplication at incremental backup will not produce much

effect because:

• The deduplicated items that have not changed are not included in the incremental backup.

• The deduplicated items that have changed are not identical anymore and therefore will not be

deduplicated.

2.14.6.4. Deduplication best practices

Follow these recommendations when using deduplication:

• When creating a deduplicating vault, place the vault and its deduplication database on different

disks. This will make deduplication faster, because deduplication involves extensive simultaneous

use of both the vault and the database.

• Indexing of a backup requires that the vault have free space with a minimum size of 1.1

multiplied by the size of the archive the backup belongs to. If there is not enough free space in

the vault, the indexing task will fail and start again after 5–10 minutes, on the assumption that

some space has been freed up as a result of cleanup or of other indexing tasks. The more free

space there is in the vault, the faster your archives will reduce to the minimum possible size.

• When backing up multiple systems with similar content, back up one of the similar systems first,

so that Acronis Backup & Recovery 10 Storage Node indexes all the system's files as potential

deduplication items. This will lead to faster backup processes and less network traffic (because of

effective deduplication at source), regardless of whether the backups are performed

simultaneously or not.

Before starting the subsequent backups, make sure that the indexing task has finished

deduplication of the first backup and is now idle. You can view the state of the indexing task in

the list of tasks on Acronis Backup & Recovery 10 Management Server.

2.14.6.5. Deduplication ratio

The deduplication ratio shows the size of archives in a deduplicating vault in relation to the size they

would occupy in a non-deduplicating vault.

For example, suppose that you are backing up two files with identical content from two machines. If

the size of each file is one gigabyte, then the size of the backups in a non-deduplicating vault will be

approximately 2 GB, but this size will be just about 1 GB in a deduplicating vault. This gives a

deduplication ratio of 2:1, or 50%.

Conversely, if the two files had different content, the backup sizes in non-deduplicating and

duplicating vaults would be the same (2 GB), and the deduplication ratio would be 1:1, or 100%.