HP StorageWorks XP Remote Web Console Software - Manual (Page 67)

Planning of Journal Volumes
Why Planning is Necessary
Data transfer speed for journal groups is affected by specifications of journal volumes that the journal
groups use. Therefore, you need to think about specifications of journal volumes to be used by journal
volumes, in order to achieve the data transfer speed that you want.
What to Consider for Planning
This section explains what you need to consider when deciding on journal volume specifications.
The following factors affect the speed for writing to and reading from journal volumes, particularly
when a temporary communication path failure occurs between the primary storage system and the
secondary storage system, or when the amount of data transferred from hosts to the primary storage
system is increasing:
• RAID configuration of the RAID groups that will contain journal volumes
• Types of physical volumes in the RAID groups that will contain journal volumes
• Frequency of access to non-journal volumes in the RAID groups that will contain journal volumes
• Data transfer speed required for the non-journal volumes mentioned above
• Disk usage rate for RAID groups
The following factor affects the time during which data transfer with hosts can continue without being
influenced by a temporary communication path failure between the primary storage system and the
secondary storage system, or without being influenced by an increase in the data to be transferred from
hosts to the primary storage system.
• Capacity of journal volumes
How to do Planning
Data Transfer Speeds for Journal Volumes
Figure 13 on page 68 illustrates how the data transfer speed (i.e., the amount of data to be transferred
per unit of time) will change as time elapses, citing different types of data transfer speed with URz.
Data transfer speed between hosts and the primary storage system goes through two phases; in one
phase the data transfer speed remains almost unchanged, and in another phase the data transfer
speed increases temporarily.
Hitachi Universal Replicator for z/OS user guide for XP12000/XP10000 Disk Arrays and SVS 200 67