HP XP P9500 Storage - Manual (Page 17)

Description Option mode
Do not set this mode if the local storage system is connected to XP12000 Disk Array, XP10000 Disk
Array, or earlier models, or to XP24000/XP20000 Disk Array with microcode earlier than
60-02-XX-XX/XX; otherwise Continuous Access Synchronous pairs may suspend.
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 primary and secondary
system. Continuous Access Synchronous 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 17)
•
Fence Level options for I/O to the P-VOL after suspension (page 21)
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 Continuous Access Synchronous on the primary and
secondary system.
•
If you are setting up Continuous Access Synchronous for disaster recovery, make sure that
secondary 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 site so that the system
administrator can monitor conditions.
Determining Round Trip Time
When you set up the Continuous Access Synchronous association between primary and secondary
system, you specify a time limit in milliseconds for data to travel from the P-VOL to the S-VOL.Round
Trip Time is used by the systems to control the initial copy pace when update copying is in progress.
(To review the Round Trip Time step, see
Configuring storage systems, defining logical paths
(page 48) .)
This section provides instructions for determining your system’s Round Trip Time.
System performance considerations 17