Operation Manual

237 Copyright © Acronis International GmbH, 2002-2015
Disk-level backup
Deduplication of disk blocks is not performed if the volume's allocation unit size—also known as
cluster size or block size—is not divisible by 4 KB.
Tip: The allocation unit size on most NTFS and ext3 volumes is 4 KB. This allows for block-level deduplication.
Other examples of allocation unit sizes allowing for block-level deduplication include 8 KB, 16 KB, and 64 KB.
File-level backup
Deduplication of a file is not performed if the file is encrypted and the In archives, store encrypted
files in decrypted state check box in the backup options is cleared (it is cleared by default).
Deduplication and NTFS data streams
In the NTFS file system, a file may have one or more additional sets of data associated with it—often
called alternate data streams.
When such file is backed up, so are all its alternate data streams. However, these streams are never
deduplicated—even when the file itself is.
7.5.7.6 How to migrate to Update 6 deduplication
What’s new in Update 6 deduplication
Starting with Update 6, Acronis Backup Storage Node has a new indexing algorithm for server-side
deduplication and a new format of the deduplication database. As a result, the following
improvements are achieved:
 Less RAM is required per terabyte of unique data: 3 GB instead of 16 GB.
 Performance degradation does not occur as the amount of stored unique data grows.
For example, the minimum of 8 GB RAM enables you to back up and recover (at a disk level) 2.6 TB of
unique data, without any performance degradation. For file-level backups, the limit is more than 12
TB. When the data reaches this size, the indexing activity fails. The error message contains a
recommendation to increase the RAM. However, the backups continue to run. If you add more RAM
to the storage node, the indexing will run again after the next backup.
New configuration parameters (p. 230) enable you to choose between the old and new indexing
algorithms and control the storage node memory allocation.
How to recreate a deduplication database
The new indexing algorithm requires the new deduplication database format. To apply this algorithm
to an old vault, you must recreate the vault’s deduplication database.
Exporting data to a newly created vault is not recommended because it requires additional time to
“assemble” the deduplicated data and additional space to temporarily store this data. Redirecting
backups from an old vault to a new vault results in a full backup of the data and a worse
deduplication ratio because the data is not deduplicated between the two vaults.
There are two methods of recreating the deduplication database:
 Re-attaching the managed vault
If the vault is encrypted, you must provide the encryption password when re-attaching the vault.
 Changing the deduplication database path