Operation Manual

229 Copyright © Acronis International GmbH, 2002-2015
7.5.7 Deduplication
This section describes deduplication, a mechanism designed to eliminate data repetition by storing
identical data in archives only once.
Starting with v11.7, Acronis Backup uses a new deduplication algorithm. The information in this
section is effective for the case when v11.7 agents back up to deduplicating vaults created on v11.7
storage nodes. When a new agent backs up to an old vault or an old agent backs up to a new vault,
the old deduplication algorithm is used. To apply the new deduplication algorithm to old backups,
you need to import the backups into a newly created vault.
7.5.7.1 Overview
Deduplication is the process of minimizing storage space taken by the data by detecting data
repetition and storing the identical data only once.
Deduplication may also reduce network load: if, during a backup, a data is found to be a duplicate of
an already stored one, its content is not transferred over the network.
Acronis Backup will deduplicate backups saved to a managed vault if you enable deduplication during
the vault creation. A vault where deduplication is enabled is called a deduplicating vault.
The deduplication is performed on data blocks. The block size varies from 1 B to 256 KB for both
disk-level and file-level backups.
Acronis Backup performs deduplication in two steps:
Deduplication at source
Performed on a managed machine during backup. The agent uses the storage node to determine
what data can be deduplicated and does not transfer the data blocks whose duplicates are
already present in the vault.
Deduplication at target
Performed in the vault after a backup is completed. The storage node analyzes the vault's
contents and deduplicates data in the vault.
When creating a backup plan, you have the option to turn off deduplication at source for that plan.
This may lead to faster backups but a greater load on the network and storage node.
Deduplication database
Acronis Backup Storage Node maintains the deduplication database, which contains the hash values
of all data blocks stored in the vault—except for those that cannot be deduplicated, such as
encrypted files.
The deduplication database is stored in the storage node local folder. You can specify the database
path when creating the vault. To minimize access time to the database, store it on a directly attached
drive rather than on a mounted network volume. For more recommendations, see "Deduplication
best practices." (p. 232)
The size of the deduplication database is about 0.05 percent of the total size of unique data stored in
the vault. In other words, each terabyte of new (non-duplicate) data adds about 0.5 GB to the
database.