HP XP Continuous Access Software - Manual (Page 112)

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 communications path failure
between the primary storage system and the secondary storage system if the master journal volume
satisfies the conditions mentioned earlier. Therefore, the data transfer speed and the volume capacity
required for the restore journal volumes are smaller than those required for the master journal
volumes. Note that the data transfer speed for the journal volumes must exceed the data transfer
speed in normal status.
Factors That Determine Data Transfer Speed Between the Primary and
Secondary Storage System
The speed of the 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 normal status, mentioned in
Figure 52 (page 112) . 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 the journal volumes.
Figure 52 Data Transfer Speed with XP Continuous Access Journal (Data Transfer Speed Between
the Primary Storage System and the Secondary Storage System)
Bandwidth of 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 normal status mentioned earlier.
Journal Transfer Speed of the DKC
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 enough so that the journal transfer speed
exceeds the data transfer speed in the normal status mentioned earlier. The maximum number of
paths for each pair of the primary DKC and the secondary DKC is 8.
112 Preparing for XP Continuous Access Journal Operations