HP XP Racks - Manual (Page 32)

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If all the data paths for Continuous Access Synchronous pairs are disconnected, but the paths
used for Cnt Ac-J pairs are connected, failure suspend does not occur and S-VOLs cannot be
changed to PSUE status.
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If you turn off the power of the primary system when S-VOLs are in PAIR status, all the data
paths for the primary system will be disconnected and all the S-VOLs registered in CG 127
will be changed to PSUE status.
Notes when you remove or resynchronize pairs by Business Continuity Manager
When you resynchronize the Continuous Access Synchronous Z pair in the Open/MF consistency
group which consists of one pair of the primary storage system and the secondary storage system
by Business Continuity Manager, all pairs in the consistency group are resynchronized. If the host
is accessing the S-VOL of the Continuous Access Synchronous pair, the Continuous Access
Synchronous pair is also resynchronized simultaneously. Resynchronize the pair after you reconfirm
the status of all Continuous Access Synchronous pairs and all Continuous Access Synchronous Z
pairs in the consistency group.
When you remove the Continuous Access Synchronous Z pair in the Open/MF consistency group
which consists of one pair of the primary storage system and the secondary storage system by
Business Continuity Manager, only the Continuous Access Synchronous Z pairs in the consistency
group are removed. If you want to remove the Continuous Access Synchronous pair simultaneously,
you should remove the pairs by RAID Manager.
Host failover software
Host failover software transfers information between host servers at the local and remote sites. It
is a critical component of a disaster recovery solution.
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When Continuous Access Synchronous is used as a disaster recovery tool, host failover is
required to ensure effective recovery operations.
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When Continuous Access Synchronous is used as a data migration tool, host failover is
recommended.
Continuous Access Synchronous does not provide host failover functions. Use the failover software
most suitable for your platform and requirements (for example, Microsoft Cluster Server).
Data path requirements and configurations
A data path must be designed to adequately manage all possible amounts of data that could be
generated by the host and sent to the P-VOL and S-VOL. This topic provides requirements and
planning considerations for the following key elements of the data path:
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“Bandwidth requirements” (page 32)
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“Fibre Channel requirements” (page 33)
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“Supported data path configurations” (page 33)
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“Ports” (page 35)
Bandwidth requirements
Sufficient bandwidth must be present to handle data transfer of all workload levels. The amount
of bandwidth required for your Continuous Access Synchronous system is based on the amount of
I/O sent from the host to the primary system. You determine required bandwidth by measuring
write-workload. Workload data is collected using performance monitoring software. Consult your
HP account team for more information.
32 Planning for Continuous Access Synchronous