Dell PowerVault DR6000 - Manual (Page 16)

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 will 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). The unique
chunks of data that represent the attachment are deduplicated at the block chunking level.
NOTE: The DR Series system does not support deduplication of any encrypted data, so there will be no
deduplication savings derived from ingesting encrypted data. The DR Series system cannot deduplicate data
that has already been encrypted because it considers that data to be unique, and as a result, cannot
deduplicate it.
In cases where self encrypting drives (SEDs) are used, when data is read by the backup application, it is decrypted by
the SED or the encryption layer. This works in the same way as if you were opening an MS-Word document that was
saved on a SED. This means that any data stored on a SED can be read and deduplicated. If you enable encryption in the
backup software, you will lose deduplication savings because each time the data is encrypted, the DR Series system
considers it to be unique.
Replication: Replication is the process by which the same key data is saved from multiple storage devices, with the goal
of maintaining consistency between redundant resources in data storage environments. Data replication improves the
level of fault-tolerance, which improves the reliability of maintaining saved data, and permits accessibility to the same
stored data. The DR Series system uses an active form of replication that lets you configure a primary-backup scheme.
During replication, the system processes data storage requests from a specified source to a specified replica and an
optional cascaded replica (for an additional copy) that acts as a replica of the original source data. With this cascaded
replication, you can send your data to a replica, plus one additional cascaded replication if you choose.
NOTE: The DR Series system software includes version checking that limits replication only between other DR
Series systems that run the same system software release version. If versions are incompatible, the administrator
will be notified by an event.
Replicas/cascaded replicas are read-only and are updated with new or unique data during scheduled or manual
replications. The DR Series system acts as a form of storage replication where the backed up and deduplicated data is
replicated in real-time or via a scheduled window. In a replication relationship between two or three DR Series systems,
this means that a relationship exists between a number of systems, one acting as the source and the other as a replica,
with a third (optional) cascaded replica if you choose to keep two instances of the replicated data in your backup
workflow.
Replication is done at the container level and is one direction from Standby Continuous Replication (SCR) to the Replica
to the Optional Cascade Replica. However, since replication is done at the container level, you can set up various
containers to meet your specific replication requirements for your specific workflow. This form of replication supports
the CIFS, NFS, Rapid CIFS, and Rapid NFS protocols and is fully handled by the DR Series appliance.
Unlike NFS and CIFS containers, OST and RDS container replication is handled by the Data Management Application
(DMA) media servers.
The DR Series system supports the 64:1 replication of data (32:1 if on the DR4X00 and 8:1 for the DR2000v), whereby up to
64 source DR Series systems can write data to different individual containers on a single, target DR Series system. This
supports the use case where branch or regional offices can each write their own data to a separate, distinct container
on a main corporate DR Series system.
NOTE: Be aware that the storage capacity of the target DR Series system is directly affected by the number of
source systems writing to its containers, and by the amount being written by each of the source systems.
If the source and target systems (replica or cascaded replica) reside in different Active Directory (AD) domains, then the
data that resides on the target DR Series system may not be accessible. When AD is used for authentication for DR
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