HP StorageWorks XP Remote Web Console Software - Manual (Page 22)

The base-journal data is stored in the entire data volume or the area for the difference. The journal
data for the entire data volume is created when the data volume pair is created. The difference
journal data is obtained when the pair status of the data volume changes from the Suspending
status to the Pair resync status. Merging the difference bitmaps that are recorded on both primary
and secondary data volumes enables you to obtain the journal data for only the difference. When
a data volume pair is suspended, the status of data that is updated from the host to the primary
and secondary data volumes is recorded to the difference bitmap.
The base-journal data of the primary storage system is stored in the secondary storage system
journal volume according to the read command from the secondary storage system. After that, the
base-journal data is restored from the journal volume to the secondary data volume. The initial
copy operation finishes when all base-journals are restored.
NOTE:
•
If you manipulate volumes (not journal groups) to create or resynchronize two or more data
volume pairs within the same journal group, the base journal of one of the pairs is stored in
the restore journal volume, and then the base journal of another pair is stored in the restore
journal volume. Therefore, the operation for restoring the latter base journal is delayed.
•
The journal obtain operation starts at the primary data volume and goes through the steps
that follow in this section.
•
You can specify None as the copy mode for initial copy operations. If the None mode is
specified, initial copy operations are not performed. Therefore, if you specify None, you are
responsible for ensuring that data in the primary data volume and secondary data volume
are identical.
•
You may create an XP Continuous Access Journal data volume pair by using XP Continuous
Access initial copy. The next steps must be done together to avoid errors:
1.
Set the appropriate system option (474) on both the primary and secondary storage
system.
2. Use the script written especially for this operation.
•
If you delete all XP Continuous Access Journal data volume pairs in a given journal group,
please wait a few minutes before creating any additional XP Continuous Access pairs.
•
When an RCU that is shared with multiple MCUs, performs the pair resume operation after
the system option mode 593 is set, if you resume 1025 or more pairs from multiple MCUs
(range: group) at the same time, the.pair resume operations may fail if system option mode
593 is not available.
Two secondary storage issues:
If you use the script without setting the system option on the secondary storage system, the following
operations occur:
1. The storage system recognizes the XP Continuous Access S-VOL as the XP Continuous Access
Journal S-VOL.
2. The SSB log (SSB=CBED) is generated in the secondary storage system.
Because of this, the command to create the pair is rejected.
A primary storage issue:
If you use the script without setting the system option on the primary storage system, normal operation
occurs. However, if there is an update I/O during the XP Continuous Access initial copy, the
processing speed of the operation is slow.
Update Copy Operation
When a host performs a write I/O operation to the primary data volume of a data volume pair,
an update copy operation is performed. During an update copy operation, the update data that
22 About XP Continuous Access Journal Operations