HP XP P9000 Continuous Access Synchronous for Mainframe Systems User Guide

DescriptionOption mode
Allows you to select whether to output the F/M = FB message to the host of MCU when the suspension
or the release operation is performed from Business Continuity Manager to the S-VOL of a Cnt Ac-S
Z pair in Duplex status:
776
• Mode 776 ON: The F/M = FB message is not output.
• Mode 776 OFF: The F/M = FB message is output.
This mode must be set to both MCU and RCU.
Allows you to reduce RIO MIH time to 5 seconds. As a result, after a data path error, the total amount
of time that elapses is reduced before the operation is retried on an alternate path. (Both RIO MIH
time and the Abort Sequence timeout value are combined for this retry time.)
784
• Mode 784 ON: Reduces the RIO MIH time to 5 seconds.
Combined with the Abort Sequence timeout value, the total amount of time that elapses before
the operation is retried on another path is a maximum of 10 seconds.
• Mode 784 OFF: The RIO MIH time that you specified at RCU registration (default=15 seconds)
is used with the specified Abort Sequence timeout value.
System performance considerations
Remote synchronous copy operations affect I/O performance on the host and main and remote
system. Cnt Ac-S Z provides options for minimizing the impact on performance and for maximizing
the efficiency and speed of copy operations for the best level of backup data integrity. These
options are discussed in:
• “Determining Round Trip Time” (page 32)
• “Fence Level options for I/O to the P-VOL after suspension” (page 36)
You can also optimize copy operations and performance with the following. Check with your HP
service provider for more information.
• Analyze write-workload. Bottlenecks severely impact performance, but the workload data you
collect (MB/s and IOPS) help determine the following key elements that, when sized properly,
form a data path that operates free of bottlenecks under all workload levels:
◦ Amount of bandwidth.
◦ Number of data paths.
◦ Number of host-interface paths.
◦ Number of ports dedicated for Cnt Ac-S Z on the main and remote system.
• If you are setting up Cnt Ac-S Z for disaster recovery, make sure that remote systems are
attached to a host server. This enables both the reporting of sense information and the transfer
of host failover information. If the remote site is unattended by a host, you should attach the
storage systems to a host server at the main or primary site so that the system administrator
can monitor conditions.
The following table lists conditions that affect storage system performance and provides
recommendations for addressing them.
RecommendationDescriptionCondition
Spread write-intensive data across several
volumes to minimize queuing.
Write-intensive workloads, such as database
logging volumes, can have a significant impact
on storage system I/O response times.
Write-intensive
workloads
Spread workloads with large write block sizes
across several volumes.
Workloads with large write block sizes, such
as DB deferred writes, can impact performance.
Large block size
System performance considerations 31