Avoiding Issues Using the 2012 AIX Performance Update
Analyzing AIX performance and avoiding potential problems in the first place are essential for any systems administrator. Several steps should be part of your plans—the first of these is enrolling for Support Notifications. These can be tailored to fit the needs of your organization, and they ensure your notified as soon as IBM publishes fixes, allowing you to be proactive in avoiding problems. Sign up for storage and system notifications here.
IBM has published fixes for a few known performance issues in AIX and POWER7. This is one reason it’s important to stay as current as possible with maintenance. No one wants to take an outage over a problem that’s already been found and has a fix available. These issues involve: affinity and dispatch, asynchronous I/O (AIO) server deadlocks, Virtual Partition Manager (VPM) serialization crashes, and slow Oracle Automatic Storage Management (ASM) startup. Specific fixes for these are available to various technology levels (TLs) in both AIX V6.1 and V7.1.
Additionally, performance issues are known around some of the older firmware levels, especially those in the 720 release. I monitor the firmware history files for my servers to check for HIPER and performance fixes. I also try to update firmware, Hardware Management Console (HMC), virtual I/O (VIO) servers and AIX at least every six months to avoid problems that have been already resolved. It’s not a guarantee but it helps avoid most issues.
For example, in AL720_064 there’s a hypervisor dispatch bug—this is fixed in the concurrent update, AL720_101. The Power Firmware Code Matrix lists the latest firmware version for all servers and provides a link to the supported HMC and server firmware combinations.
Remember, when updating firmware, it’s critical to read the firmware description file, especially the sections titled “Minimum HMC Code Level” and “Important Information.” If the HMC isn’t at the minimum code level listed, then it should be updated prior to any upgrades to firmware.
You can also use the Fix Level Recommendation Tool (FLRT) to make recommendations for system levels. FLRT provides details on updates, including release and end-of-support dates. You can also click through to order the updates with it.
To avoid performance problems, I use a set of starter tunables whenever I set up a system. For AIX V6 and V7, I take the new defaults for the memory tunables (i.e. maxperm%, etc.) These are now restricted tunables that should only be changed if you have a problem management record (PMR) open and IBM tells you to do so. If this happens then you should record the PMR number, what the change was and why it was made.
I also recommend periodically validating that the recommendation is still valid. I work on many performance problems where a change was made because of a problem at a specific TL and subsequent OS updates mean that change is no longer valid and might actually be causing problems.
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