Optimizing Continuous Access Xp Operations And Disk Array Performance - HP xp12000 User Manual

Table 25 Remote copy I/O statistics (continued)
Statistic
Scheduling Attempt Count
Synchronization
Pair Synchronized (%)
Out of Synchronous Tracks
Cache
SideFile[%]
The usage monitor graph closes automatically in the following cases:
• Stopping the usage monitoring function by clicking Stop in the Operation drop-down list, and clicking
Apply.
• Clicking another tab.
• Exiting Command View XP or XP Remote Web Console.

Optimizing Continuous Access XP operations and disk array performance

Continuous Access XP operations result in increased utilization of the disk array's channel resources
because of additional write (remote copy) operations to secondary volumes. The Continuous Access XP
update copy mode (synchronous or asynchronous) determines exactly how the remote copy operations
impact disk array performance as follows:
• Synchronous copy mode has an additional effect on disk array performance: increased service and
disconnect time for write I/Os to Continuous Access XP P-VOLs due to the delay between channel-end
and device-end. The length of this delay increases as the distance between the P-VOL and S-VOL
increases, so the longest delay occurs when primary and secondary volumes are the maximum
distance apart.
• Asynchronous copy mode (Continuous Access XP Asynchronous) eliminates all delays associated with
Continuous Access XP Synchronous operations while providing protection for write-dependent
applications if a disaster occurs. Write I/Os for Continuous Access XP Async P-VOLs are processed the
same way as writes for simplex volumes, without any increase in service or disconnect time.
Asynchronous S-VOL updates are performed completely independent of all host I/O processes at
P-VOLs, and there are no restrictions on subsequent read and write operations to Continuous Access XP
Async P-VOLs. The only performance concerns for Continuous Access XP Asynchronous are:
• Ensuring adequate cache resources are available for sidefiles used to store recordsets at MCUs and
RCUs
• Ensuring sufficient Fibre Channel paths are defined for copy operations
In addition to Continuous Access XP update copy mode, several other factors can also affect disk array
performance. You can optimize Continuous Access XP operations and I/O performance of disk arrays by
analyzing workloads and addressing system-level conditions (for example, number of Fibre Channel paths)
that can affect disk array performance. You can also control the impact of Continuous Access XP
operations on disk array performance by selecting the appropriate RCU options for each MCU (see
"Registering RCUs (Add
page 71) and the appropriate update copy mode (synchronous or asynchronous) and pair options (see
"Creating Continuous Access XP volume pairs
pair. In addition, you can upgrade Continuous Access XP hardware components and adjust the
configuration of components to improve disk array performance under a wide range of operating
conditions.
Description
Number of job activations of consistency manager
Percent completion of initial copy operations. For example, number of
synchronized pairs/total number of pairs.
Number of tracks that have not yet been copied by initial copy or resync copy
operations. This applies only when suspended during initial copy or during
resync copy.
You can select only this option when you select Subsystem Total or CLPR in Select
LU on the Display Item pane.
RCU)" on page 66 and
(Paircreate)" on page 93) for each Continuous Access XP
Continuous Access XP user guide for the XP12000/XP10000
"Modifying RCU options (Change RCU Option)" on
87