Acronis Backup & Recovery 10 Adv WS TIDLBPDES Manuale Utente
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TIDLBPDES
disk space (say, 1 GB); the files that are specific to each machine occupy the other 50% (another
1 GB).
1 GB).
In a deduplicating vault, the size of the first machine's backup in this case will be 2 GB, and that of the
second machine will be 1 GB. In a non-deduplicating vault, the backups would occupy 4 GB in total. As
a result, the deduplication ratio is 4:3, or about 1.33:1.
second machine will be 1 GB. In a non-deduplicating vault, the backups would occupy 4 GB in total. As
a result, the deduplication ratio is 4:3, or about 1.33:1.
Similarly, in case of three machines, the ratio becomes 1.5:1; for four machines, it is 1.6:1. It
approaches 2:1 as more such machines are backed up to the same vault. This means that you can
buy, say, a 10-TB storage device instead of a 20-TB one.
approaches 2:1 as more such machines are backed up to the same vault. This means that you can
buy, say, a 10-TB storage device instead of a 20-TB one.
The actual amount of capacity reduction is influenced by numerous factors such as the type of data
that is being backed up, the frequency of the backup, and the backups' retention period.
that is being backed up, the frequency of the backup, and the backups' retention period.
2.11.6.4. How deduplication works
Deduplication at source
When performing a backup to a deduplicating vault, Acronis Backup & Recovery 10 Agent reads items
being backed up—disk blocks for disk backup or files for file backup—and calculates a fingerprint of
each block. Such a fingerprint, often called a hash value, uniquely represents the item's content
within the vault.
being backed up—disk blocks for disk backup or files for file backup—and calculates a fingerprint of
each block. Such a fingerprint, often called a hash value, uniquely represents the item's content
within the vault.
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.
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. 68).
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. 68).
Deduplication at target
After a backup to a deduplicating vault is completed, the storage node deduplicates data in the vault
as follows:
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.
that cannot be deduplicated remain in the archives.
2. In the archives, it replaces the moved items with the correspondent 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.
more references to it from the vault's archives.
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.
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.
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