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Improve Power Systems Server Performance With Enhanced Tools

The IBM Power Systems announcements in October 2012 featured several performance tool enhancements. Three of those tools are designed to help tune your system:

  1. Virtual I/O Server (VIOS) Performance Advisor
  2. Active System Optimizer (ASO)
  3. Dynamic Platform Optimizer (DPO)

The VIOS Performance Advisor and ASO affect the specific LPARs where they’re run. The Dynamic Platform Optimizer runs at a system level and can improve the performance of all LPARs within a system.

VIOS Performance Advisor

The VIOS Performance Advisor collects VIOS system data for a specified period of time and then generates a health check report. The health check report provides status and recommended tuning changes, if needed, for the following system resources: CPUs, memory, fibre channel (FC) adapters and disk performance. The recommended changes aren’t automatically implemented, however, the output report does provide the appropriate commands to implement the recommendations.

VIOS CPU configuration (dedicated or shared), entitlements and consumption are listed in the report along with shared pool utilization. The performance advisor will look for insufficient CPU allocation for the VIOS as well as over-utilization of the shared processor pool. VIOS memory configuration and usage is analyzed to see if memory settings are causing performance issues. Parameters that are checked include: Memory size, paging, swap space and pinned memory. The VIOS performance advisor can detect and report on over-saturated FC adapters. FC adapter I/Os per second are reported along with adapter utilization and operating speed. The advisor also looks for overstressed VIOS disks based on latencies and drive saturation.

The VIOS Performance Advisor is run using the command-line interface on the VIOS server. Data is collected every 15 seconds during the user-specified run time of 15 to 60 minutes. Once assembled, the data files and an XML report file are saved to disk.

The advisor is included as a standard feature of VIOS beginning with version and is included with all three version of PowerVM (Express, Standard and Enterprise). This tool has also been referred to as the VIOS Health Advisor and was previously available on IBM developerWorks.

Active System Optimizer

ASO automatically tunes running, AIX LPARs. Formerly provided only with AIX 7.1 TL1, it’s now included with AIX 6.1 TL8 at no additional charge. ASO addresses these system elements:

  • Memory affinity
  • Workload placement
  • Dynamic page sizes
  • Memory pre-fetch controls
  • Simultaneous multithreading mode
  • CPU pipeline controls and branch prediction

Each of these items is automatically tuned while your AIX-based LPAR is running. Note that APO needs to be run on each LPAR you want to automatically tune. It runs under the AIX System Resource Controller subsystem. The parameter is aso. It runs in the background and makes changes as needed. Operation of ASO is supported on POWER7 and POWER7+ systems.

An optional, chargeable feature that works with APO is the AIX Dynamic System Organizer (DSO). Like APO, DSO makes changes only to the LPAR where it’s running. It provides two additional features:

  • Enabling the AIX partition to dynamically change the memory page size for best performance
  • Dynamically adjusting memory pre-fetch

Both of these are automatically updated as the system runs. DSO is particularly helpful for systems running large database workloads.

DSO works with AIX 6.1 TL8 and AIX 7.1 TL2. It’s bundled with AIX Enterprise Edition and is available for an additional charge for use with the standard edition. Its IBM product number is 5765-PWO.

Dynamic Platform Optimizer

The DPO tool helps improve the affinity between processor cores and memory for LPARs running on a server. When it’s used, each LPAR’s CPUs and memory are rearranged for optimal performance. DPO works with dedicated and virtualized partitions. It’s transparent to the applications running on the LPARs while they’re being optimized.

DPO is a hypervisor-based function initiated from the Hardware Management Console command line. The specific DPO command is optmem. It can be run against all of the LPARs on a system or a user-specified list of LPARs. As a preliminary check, running the lsmemopt command will show the current system configuration and a view of the optimized configuration. During DPO operation, the hypervisor will make use of installed capacity-on-demand memory to improve DPO processing and outcomes.

DPO works with POWER7 or POWER7+ servers, running system firmware version 7.6 or higher. The following servers are currently available with system firmware 7.6: POWER7+ models 770 and 780 (9117-MMD & 9179-MHD) as well as the revised POWER7 Model 795 (9119-FHB). IBM has issued a statement of direction indicating planned support for firmware 7.6 on POWER7-based Model 770 and 780 servers (9119-MMC and 9170-MHC). DPO is ordered as a no-charge feature code on the supported servers. AIX 6.1 TL8, AIX 7.1 TL2 or higher is required to run DPO.

When running DPO, LPAR performance will typically degrade by approximately 10 to 20 percent during the relocation process. DPO and an active Live Partition Mobility move cannot occur at the same time on an LPAR. Dynamic memory changes are not allowed during the relocation process, and DPO is not supported with LPARs using Active Memory Sharing.

Improve Server Performance

Using best practices and expert knowledge, IBM continues to enhance Power Systems performance-monitoring tools. Offering more than basic data collection, these tools provide recommended changes (VIOS Performance Advisor) and even automate system adjustments (ASO and DPO). Implementing them in your environment can enable you to keep your systems running at peak performance.

Charlie Cler supports customers in a solutions-architect role at Forsythe Technology Inc. He can be reached at

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