Intel 7xx Servers User Manual

NOTE: The information that follows is based on performance measurements and analysis done in the
Server Group Division laboratory.  Actual performance may vary significantly from these tests. 

6:55

10:19

4:31

Time(Minutes)

Active Partitions

Active Switchovers

Inactive Switchovers

When planning an iSeries availability solution consider the characteristics of IASPs, as well as their
advantages and disadvantages.  For example, consider these statements regarding switched disks or IASPs
when determining their value in an availability solution:

y

For a faster vary on, keep the user-ID(UID) and group-ID(GID) of user profiles that own objects
on the IASP the same between nodes of the cluster group.  Having different UID’s lengthens the
vary on time significantly.

y

The time to vary on an IASP during the switching process depends on the number of objects on
the IASP, and not the size of the objects.  If possible, keep the number of objects small.

y

The number of devices in a tower affects switchover time.  A larger number of devices in a
switchable resource increases switchover time because devices must be reset.

y

Keep the number of database objects in SYSBAS low on both systems.  Larger number of objects
in SYSBAS can slow the switchover.

A variety of scenarios exist in Cross-Site Mirroring that could be tested for performance.  The best
representative scenarios for the majority of our customers was measured.

With Geographic Mirroring we assessed the performance of the following components:

Synchronization: The geographic mirroring processing that copies data from the production copy to the
mirror copy. During synchronization the mirror copy contains unusable data. When synchronization is
completed, the mirror copy contains usable data.

Three resume priority options exist which may affect synchronization performance and time.  Resume
priority of low, medium, and high for geographic mirroring will affect the CPU utilization and the speed
at which data is transferred.  The default value is set at medium.  A system set at high will transfer data
faster and consume more CPU than a lower setting. Your choice will depend on how much time and CPU
you want to allocate for this synchronization function.

 
Switchable IASP’s using Geographic Mirroring:  Refer to the switchable IASP’s for a description of the
different switchover scenarios that can occur using switchable IASP’s with geographic mirroring.

IBM i 6.1 Performance Capabilities Reference - January/April/October 2008

©

 Copyright IBM Corp. 2008