Replication - Dell DR4000 Administrator's Manual

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By contrast, standard file compression tools identify short repeated substrings
inside individual files, with the intent of storage-based data deduplication
being to inspect large volumes of data and identify large amounts of data such
as entire files or large sections of files that are identical.
Once this has been done, this process allows for the system to store only one
copy of the specific data. This copy may be additionally compressed using
single-file compression techniques.
For example, there may be cases where an email system may contain 100 or
more emails where the same 1 megabyte (MB) file is sent as an attachment
and the following shows how this is handled:
• Without data deduplication, each time that email system is backed up, all
100 instances of the same attachment are saved, which requires 100 MB of
storage space.
• With data deduplication, only one instance of the attachment is actually
stored (all subsequent instances are referenced back to the one saved
copy), with the deduplication ratio being approximately 100 to 1).
NOTE:
The DR4000 system does not support deduplication of any encrypted data,
so, there will be no deduplication savings derived from ingesting encrypted data.
The DR4000 system cannot deduplicate data that has already been encrypted
because it considers that data to be unique, and as a result, cannot deduplicate it.
For the case where you self encrypting drives (SEDs) were used, when data is
read by the backup application it is decrypted by the SED or the encryption
layer (for example, as if you were opening an MS-Word document that was
saved on a SED). If you enable encryption in the backup software, you will
lose deduplication savings because each time the data is encrypted, the
DR4000 system considers it to be unique.

Replication

Replication is the process by which the same saved data is saved from
multiple storage devices, with the goal of maintaining consistency between
redundant resources in data storage environments.
Data replication improves fault-tolerance, which improves the reliability of
maintaining saved data, and permitting accessibility to the same stored data.
The DR4000 system uses an active form of replication that lets you configure
a primary-backup scheme in which the system processes data storage requests
from a specified source to a specified destination or replica.
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Understanding the DR4000 System