The data transfer speed of a journal volume depends on the data transfer speed of the RAID group that the journal volume belongs. One RAID group can consist of one or more volumes, including journal volumes. Therefore, if frequent accesses are made to
Arranging Journal Volumes
The following indicates the data transfer speed of journal volumes mentioned earlier in section Computing Required Data Transfer Speeds for Journal Volumes.
If a host attempts to write data of "aa" kilobytes and the number of write I/Os per second is "bb", the data transfer speed required for journal volumes is calculated as follows:
Data transfer speed of journal volumes > aa ⋅ bb ⎟ 1,024 (MB/sec)
The data transfer speed of journal volumes must exceed the data transfer speed from hosts to the primary storage system. You must consider the data transfer speed (i.e., the speed for writing and reading) required for journal volumes, determine physical volume configuration and RAID configuration of RAID groups, and create journal volumes in the RAID groups.
Computing the Journal Volume Capacity
In Figure
If a temporary communication path failure occurs between the primary storage system and the secondary storage system, journal transfers between the primary storage system and the secondary storage system will stop temporarily. If hosts transfer data to the primary storage system while journal transfers between the primary storage system and the secondary storage system are stopped temporarily, all the data transferred from hosts to the primary storage system will be stored as journal data in journal volumes.
Chapter 3 Preparing for Universal Replicator z/OS Operations |
