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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. 318), under "Change the compacting task schedule".
You can also manually start or stop the task from the
Tasks
view.
2.14.6.3
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.
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.
