HP XP P9500 Storage - Manual (Page 20)

3 Planning volumes and systems
This chapter provides information and instructions for planning Continuous Access Journal volumes,
P9500 systems, and other important requirements and restrictions.
Plan and design workflow
Planning the Continuous Access Journal system is tied to your organization’s business requirements
and production system workload. This means defining business requirements for disaster downtime
and measuring the amount of changed data your system produces over time. With this information,
you can calculate the size that journal volumes must be and the amount of bandwidth required to
transfer update data over the data path network.
The plan and design workflow consists of the following:
•
Assess your organization’s business requirements to determine recovery requirements.
•
Measure your host application’s write-workload in MB per second and write-input/output per
second (IOPS) to begin matching actual data loads with the future Continuous Access Journal
system.
•
Use collected data along with your organization’s recovery point objective (RPO) to size
Continuous Access Journal journal volumes. Journal volumes must have enough capacity to
hold accumulating data over extended periods.
The sizing of journal volumes can be influenced by the amount of bandwidth you settle on.
Both efforts are interrelated. You may actually adjust journal volume size in conjunction with
bandwidth to fit the organization’s needs.
•
Use IOPS to determine data transfer speed into and out of the journal volumes. Data transfer
speed is determined by the number of Fibre Channel ports you assign to Continuous Access
Journal, and by RAID group configuration. You need to know port transfer capacity and the
number of ports that your workload data will require.
•
Use collected workload data to size bandwidth for the fibre channel data path. As mentioned,
bandwidth and journal volume sizing, along with data transfer speed, are interrelated.
Bandwidth may be adjusted in conjunction with the journal volume capacity and data transfer
speed you plan to implement.
•
Design the data path network configuration. This involves understanding supported
configurations, the need for fibre channel switches, the number of ports your data transfer
requirements call for.
•
Plan data volumes (primary and secondary volumes). This involves understanding the sizing
of P-VOL and S-VOL, RAID group considerations, and so on.
•
Understand operating system requirements for data and journal volumes.
•
Adjust cache memory capacity for Continuous Access Journal.
Some tasks will be handled by HP personnel. The planning information you need to address is
provided in the following sections.
Assessing business requirements for data recovery
In a Continuous Access Journal system, when the data path continues to transfer changed data to
the remote site, journals remain fairly empty. However, if a path failure or a prolonged spike in
write-data that is greater than bandwidth occurs, data is stored in the journal. Changed data that
is no longer moving to the remote system builds up in the master journal.
20 Planning volumes and systems