HP XP P9500 Storage User Manual
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sequence information remain with the data as it moves to the master and restore journals and
then to the secondary volume.
•
With RAID Manager consistency groups, when a pair is split from the S-VOL side (P-VOL status
= PAIR), each storage system copies the latest data from the P-VOLs to the S-VOLs. P-VOL time
stamps might differ by storage system, depending on when they were updated.
•
Disaster recovery can be performed with multiple storage systems, including those with Cnt
Ac-J and Cnt Ac-J Z journals, using RAID Manager. See
“Switching host operations to the
for information
•
Time stamps issued by RAID Manager and the mainframe host are different. The time stamps
issued by the mainframe host become invalid when the Cnt Ac-J Z journal is included in a
RAID Manager consistency group.
•
Restoring data to the secondary system is performed when the time stamp of the copied journal
is updated. The recommended interval between time stamps is one second.
Consider the following before setting the interval:
◦
I/O response time slows when time stamps are updating among multiple storage systems.
If you shorten the interval, more time stamps are issued, resulting in an I/O response time
that is slower yet.
◦
If the interval is lengthened, the amount of time that journal data can accumulate increases,
which results in an increased amount of data to be copied.
◦
None of the above is true during the initial copy or resynchronization. During these
operations, lengthening the interval between time stamps does not result in more
accumulated journal data, because data restoring takes place regardless of time stamp.
•
The recommended method for executing RAID Manager commands is the in-band (host-based)
method. This prevents I/O response from deteriorating, which may occur with the out-of-band
(LAN-based) method.
•
Do not register a Cnt Ac-J Z journal in an EXCTG if it is included in a RAID Manager consistency
group. A journal is automatically released from the EXCTG when the RAID Manager pair
resynchronization operation is performed.
•
When Cnt Ac-J and Cnt Ac-J Z journals are in the same RAID Manager consistency group, an
error in one journal can cause suspension of all journals. See
for more information:
•
In a RAID Manager consistency group containing both Cnt Ac-J and Cnt Ac-J Z journals, data
consistency is maintained in a Cnt Ac-J system when its storage system’s microcode is changed
to a version previous to 70-03-0x. However, you cannot lower the microcode for the Cnt Ac-J
Z storage system.
•
It is not possible to register a journal to multiple RAID Manager consistency groups.
Multiple journals per RAID Manager consistency group
This section applies when you include Cnt Ac-J and Cnt Ac-J Z journals in a RAID Manager
consistency group. It does not apply to pairs consisting of only Cnt Ac-J Z volumes.
Normally, only one journal can be registered in a RAID Manager consistency group. With multiple
P9500 systems, however, up to four journals, including Cnt Ac-J Z and Cnt Ac-J journals, can be
registered in a RAID Manager consistency group. The following figures show different configurations
in which multiple journals are registered in a single RAID Manager consistency group.
Planning Cnt Ac-J Z in multiple P9500s using a consistency group
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