Intel AS/400 RISC Server, 170 Servers, 7xx Servers manual Switchover Tips, Geographic Mirroring

Switchover Measurements

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.

Switchable IASP’s using Hardware Resources

Time Required to Switch the IASP using Hardware Resources

	Inactive Switchovers	Active Switchovers	Active Partitions
Time(Minutes)	4:31	10:19	6:55

Switchover Tips

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:

yFor 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.

yThe 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.

yThe 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.

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

21.2 Geographic Mirroring

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	Chapter 21 High Availability Performance	328