Hitachi MP-96RD625-01 manual Mcu

Data transfer

speed

Data transfer speed of journal volumes

Data transfer speed

between the MCU and the RCU

Data transfer speed

between hosts and

the MCU

Time

Normal status	Temporary increase in
	data to be transferred

Figure 3-32 Data Transfer Speed with URz (Influence on Journal Volume Capacity)

The following factors determine the required journal volume capacity:

•the period of time during which data transfer can continue between hosts and the primary storage system when a temporary increase in transferred data occurs or when a communication path failure occurs between the primary and secondary storage system.

•the data transfer speed for the period of time that is mentioned above

To determine the journal volume capacity, use the following formula. In this formula, VH-Mis the data transfer speed between hosts and the primary storage system. VM-Ris the data transfer speed between the primary storage system and the secondary storage system. t is the length of time during which data transfer can continue.

Journal volume capacity > VH-M- VM-R⋅ t

If you want to calculate journal volume capacity that is required when a communication path failure occurs between the primary storage system and the secondary storage system, please assign 0 (zero) to VM-R.

The total capacity of journal volumes in each journal group must exceed the value illustrated above.

3-58 Chapter 3 Preparing for Universal Replicator z/OS Operations

Hitachi Universal Replicator for IBM /OS User’s Guide