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

Replication blackout windows
The replication process can be delayed from running using blackout windows that may be configured
using the StoreOnce GUI. Up to two separate windows per day, which are at different times for
each day of the week, may be configured.
The best practice is to set a blackout window throughout the backup window so that replication
does not interfere with backup operations. If tape copy operations are also scheduled, a blackout
window for replication should also cover this time.
Care must be taken, however, to ensure that enough time is left for replication to complete. If it is
not, some items will never be synchronized between source and target and the StoreOnce Backup
system will start to issue warnings about these items.
The replication blackout window settings can be found on the StoreOnce Management Interface
on the HP StoreOnce - Replication - Local Settings – Blackout Windows page.
Figure 44 Configuring replication blackout windows
Replication bandwidth limiting
In addition to replication blackout windows, the user can also define replication bandwidth limiting;
this ensures that StoreOnce replication does not swamp the WAN with traffic, if it runs during the
normal working day.
This enables blackout windows to be set to cover the backup window over the night time period
but also allow replication to run during the day without impacting normal business operation.
Bandwidth limiting is configured by defining the speed of the WAN link between the replication
source and target, then specifying a maximum percentage of that link that may be used.
Again, however, care must be taken to ensure that enough bandwidth is made available to
replication to ensure that at least the minimum (2 Mb/s per job) speed is available and more,
depending on the amount of data to be transferred, in the required time.
Replication bandwidth limiting is applied to all outbound (source) replication jobs from an appliance;
the bandwidth limit set is the maximum bandwidth that the StoreOnce Backup system can use for
replication across all replication jobs.
The replication bandwidth limiting settings can be found on the StoreOnce Management Interface
on the HP StoreOnce - Replication - Local Settings - Bandwidth Limiting page.
There are two ways in which replication bandwidth limits can be applied:
• General Bandwidth limit – this applies when no other limit windows are in place.
• Bandwidth limiting windows – these can apply different bandwidth limits for times of the day
A bandwidth limit calculator is supplied to assist with defining suitable limits.
Controlling Replication 87