HP StorageWorks XP Remote Web Console Software - Manual (Page 102)

Planning the Data Transfer Speed before Reversing Data Volumes
When a failure occurs at a host, one of the failure recovery measures is to reverse the primary
data volume and the secondary data volume (that is, change the copy direction). To reverse the
primary data volume and the secondary data volume, usually you must ensure that the data transfer
speed is the same before and after you reverse these data volumes. Therefore, when you do
planning for master journal volumes and restore journal volumes, you need to apply the same
scheme to both master and restore journal volumes.
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 that the data transfer speed for journal volumes must exceed the data transfer speed in normal
status.
Contributing Factors for the 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 the 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 the normal status mentioned in the following figure. 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.
Figure 44 Data Transfer Speed with Universal Replicator for Mainframe (Data Transfer Speed
between the Primary Storage System and the Secondary Storage System)
Bandwidth for Data Transfer Paths
The bandwidth (that is, the data transfer speed) of the 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 the 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
102 Preparing for Universal Replicator for Mainframe Operations