HP StoreOnce Backup System Concepts and Configuration Guidelines (BB877-90913, November 2013)

11 Replication
When considering replication you are likely to be synchronizing data between different models
of HP StoreOnce Backup Systems. The examples in this section are not specific to a particular
model of HP StoreOnce Backup System.
Replication can take place between multi-node and single-node StoreOnce Backup Systems. The
GUI for both refers to both Replication Targets and Sources as appliances. It is important to
understand the different meaning of appliance within the multi-node and single-node environment.
• In a single-node StoreOnce Backup System, the appliance is the physical device or server that
contains the data to be replicated. All mapping is done using the physical IP addresses of the
target and source StoreOnce Backup Systems.
• In a multi-node StoreOnce Backup System, the appliance is the service set that contains the
data to be replicated. This means that each B6000 Backup System has at least two service
sets that can be selected as appliances. All mapping is done using the virtual IP addresses of
the target and source service sets.
Within this chapter the term appliance and service set are synonymous.
What is replication?
Replication is a standard term used to describe a way of synchronizing data between hardware
in two physical locations. It is the process of creating an exact match on the target appliance of
the specified data from the source appliance. It is important to understand that no history is held;
the target appliance always mirrors as soon as possible the current state of the data on the source
appliance, which means that it is ready for use if the source share, library or appliance is
unavailable. But it does not hold archive versions and is not an alternative to conventional backup
with multiple restore points. A Configuration Wizard is provided to take you through HP StoreOnce
Replication configuration steps.
StoreOnce replication is a concept that is used with VTL and NAS devices. The equivalent concept
for Catalyst store is called Catalyst Copy.
All three device types use a deduplication-enabled, low bandwidth transfer policy to replicate data
from a device on a “replication source” StoreOnce Backup system to an equivalent device on
another “replication target” StoreOnce Backup system. The fundamental difference is that the
backup application controls Catalyst store copy operations, whereas all VTL and NAS replication
is configured and managed on the StoreOnce Management GUI.
Replication provides a point-in-time “mirror” of the data on the source StoreOnce device at a target
StoreOnce Backup system on another site; this enables quick recovery from a disaster that has
resulted in the loss of both the original and backup versions of the data on the source site.
Replication does not however provide any ability to roll-back to previously backed-up versions of
data that have been lost from the source StoreOnce Backup system. For example, if a file is
accidentally deleted from a server and therefore not included in the next backup, and all previous
versions of backup on the source StoreOnce Backup system have also been deleted, those files
will also be deleted from a replication target device as the target is a mirror of exactly what is on
the source device. The only exception to this is if a Catalyst device type is used because the retention
periods of data on the Target can be different (greater in most cases) than the retention periods
at the source – giving an additional margin on data protection.
NOTE: For examples on using Catalyst Copy with specific backup applications see HP StoreOnce
Backup system Summary of Best Practices for VTL, NAS, StoreOnce Catalyst and Replication
implementations with sizing and application configuration examples.
What is replication? 77