HP StorageWorks XP Remote Web Console Software - Manual (Page 70)

If you do not want to reverse the primary data volume and the secondary data volume, you will be able to
cope with a temporary increase in data transfers and a communication path failure between the primary
storage system and the secondary storage system, if the master journal volume satisfies conditions
mentioned earlier. Therefore, the data transfer speed and the volume capacity required for restore journal
volumes are smaller than those required for master journal volumes.
NOTE:
The data transfer speed for journal volumes must exceed the data transfer speed in "normal status."
Contributing Factors for Data Transfer Speed between Storage Systems
The speed of data transfer between the primary storage system and the secondary storage system
depends on the following factors:
• The bandwidth of data transfer paths
• The journal transfer speed of the DKC
The data transfer speed between the primary storage system and the secondary storage system must
exceed the data transfer speed in "normal status" mentioned in Figure 15 on page 70 below. If a
temporary increase in transferred data occurs and the data transfer speed between the primary storage
system and the secondary storage system is exceeded, the excess data will be stored temporarily in
journal volumes.
Data transfer
Data transfer speed
between hosts and
the MCU
Data transfer speed of journal volumes
Data transfer speed
between the MCU and the RCU
Time
speed
Normal status Temporary increase in
data to be transferred
Figure 15 Data Transfer Speed with URz (Data Transfer Speed between the Primary
Storage System and the Secondary Storage System)
Bandwidth for Data Transfer Paths
The bandwidth (i.e., the data transfer speed) of data transfer paths between the primary storage system
and the secondary storage system depends on the user’s environment. The bandwidth must exceed the
data transfer speed in "normal status" mentioned earlier.
DKC Journal Transfer Speed
The journal transfer speed of the DKC depends on the number of paths used for transferring journals. The
number of paths for transferring journals must be so enough that the journal transfer speed exceeds the
70 Preparing for Universal Replicator z/OS Operations