HP StorageWorks XP24000 Continuous Access Journal Software User and Reference Guide, v01 (T5278-96001, June 2007)
more mirrors in one journal group. The same Mirror ID is applied to the pair of data volumes. See
“Continuous Access Synchronous (3DC Cascading Configuration)” on page 58 for 3D C configurations.
•
Table 16 on page 46 shows specifications for the relationship between the data volumes, between
the
journal volumes, and between the d ata volume and journal volume i n the journal group.
Table16VolumeSpecifications in a Journal Group
Item
Support Specifications
Emulation type
Same or different emulation t ypes is available.
Note:
Only Open-V can be used for journal volumes.
Volume capacity
Same or different amount of capacity is available.
CLPR
Journal volumes and data volumes in the same journal group can belong to
different CLPRs. Journal volumes must belong to the same CLPR. Data volumes must
also belong to the same CLPR.
Note
: A primary journal group and the corresponding secondary journal group
need not belong to the same CLPR.
Note:
When Continuous Access Journal and TrueCopy for Mainframe coexist in the same storage system,
each journal group must contain either Continuous Access Journal pairs or TrueCopy for Mainframe
pairs (not both).
Accessing
Continuous Access Journal Primary Data Volumes and Secondar y
Data Volumes
To ensure m
aximum data integrity during normal Continuous Access Journal operations, the secondary
storage system rejects all write operations issued by a host to a Continuous Access Journal sec ondary data
volume. If you need a write operation to a Continuous Access Journal secondary data volume, you must
set the secondary da ta volume write option (see “Secondar y Data Volume Write Option” on page 29).
When you r
esume (Pairresync) the split pair, the secondary storage system will send the secondary data
volume t
rack bitmap to the primary storage system to ensure proper resynchronization of the pa ir.
Cacheand NonvolatileStorage (NVS)
Cache and nonvolatile storage (NVS) must be operable for both the primary storage system and
secondar y storage system of a Continuous Access Journal data volume pair. If not, the Continuous
Access Journal paircreate operation will fail. The remote storage system cache should be configured
to
adequately support the Continuous Access Journal remote copy workloads as well as any local
workload activity.
Host Failover Software
The Re
mote Web Console software product does not provide any host failover functions for disaster
recovery. Host failover software is a critical component of any disaster recovery effort. When a primary
storage system fails to maintain synchronization of a Continuous Access Journal pair, the primary storage
system generates sense information. It is very important that this information be transferred to the remote
site via the host failover software for effective disaster recovery.
Duplicate Volumes
Since the contents of the primary d ata volume and secondary data volume of a Continuous Access
Journal pair are identical, the secondary data volume can be considered a duplicate of the primary data
volume. Since the host operating system does not allow d uplicate volumes, the host system administrator
must take precautions to prevent system problems related to duplicate volumes. You must de fine the
Continuous Access Journal secondary d a ta volume so it does not auto-mount or come online on the same
host at the same time as the primary data volume (see
WARNING
below) .
46
Preparing for Continuous Access Journal Operations