HP XP P9500 Storage - Manual (Page 33)

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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 CTG 127
will be changed to PSUE status.
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 33)
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Fibre Channel requirements (page 33)
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Supported data path configurations (page 34)
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Ports (page 36)
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 volume. You determine required bandwidth by measuring
write-workload. Workload data is collected using performance monitoring software. Consult your
HP account team for more information.
Fibre Channel requirements
The primary and secondary system must be connected using multimode or single-mode optical
fibre cables.
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For distances between .5 km to 1.5 km, one switch is required, but you can use a maximum
of two switches.
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For distances up to 1.5 km (4,920 feet), multimode shortwave Fibre Channel interface cables
are used.
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For distances from 1.5 km to 10 km, (4,920 feet to 6.2miles) single mode longwave optical
fibre cables are required.
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For distances from 10 km to 30 km (6.2 to 18.6 miles), single-mode longwave Fibre Channel
interface cables with up to two switches are required.
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For distances greater than 30 km, approved third-party channel extender products and
telecommunications lines are required. Continuous Access Synchronous operations typically
do not extend past 30 km.
Host failover software 33