ACRONIS Backup & Recovery 10 Advanced Server User's Guide download pdf (Page 75)

Before sending the item to the vault, the agent queries the deduplication database to determine

whether the item's hash value is the same as that of an already stored item.

If so, the agent sends only the item's hash value; otherwise, it sends the item itself.

Some items, such as encrypted files or disk blocks of a non-standard size, cannot be deduplicated,

and the agent always transfers such items to the vault without calculating their hash values. For more

information about restrictions of file-level and disk-level deduplication, see Deduplication restrictions

(p. 77).

Deduplication at target

The storage node performs deduplication at target in a managed vault by running two tasks: the

indexing task and the compacting task.

Indexing task

After backup to a deduplicating vault is completed, the storage node runs the indexing task to

deduplicate data in the vault as follows:

1. It moves the items (disk blocks or files) from the archives to a special folder within the vault,

storing duplicate items there only once. This folder is called the deduplication data store. Items

that cannot be deduplicated remain in the archives.

2. In the archives, it replaces the moved items with the corresponding references to them.

As a result, the vault contains a number of unique, deduplicated items, with each item having one or

more references to it from the vault's archives.

The indexing task may take considerable time to complete. You can see this task's state in the Tasks

view on the management server.

Compacting task

After one or more backups or archives have been deleted from the vault—either manually or during

cleanup—the vault may contain items which are no longer referred to from any archive. Such items

are deleted by the compacting task, which is a scheduled task performed by the storage node.

By default, the compacting task runs every Sunday night at 03:00. You can re-schedule the task as

described in Operations with storage nodes (p. 329), under "Change the compacting task schedule".

You can also manually start or stop the task from the Tasks view.

2.13.6.3. When deduplication is most effective

The following are cases when deduplication produces the maximum effect:

• When backing up in the full backup mode similar data from different sources. Such is the case

when you back up operating systems and applications deployed from a single source over the

network.

• When performing incremental backups of similar data from different sources, provided that the

changes to the data are also similar. Such is the case when you deploy updates to these systems

and apply the incremental backup. Again, it is recommended that you first back up one machine

and then the others, all at once or one by one.

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ACRONIS Backup & Recovery 10 Advanced Server User's Guide Page 75