PowerPath: How does PowerPath "flaky path reporting" work
Summary: PowerPath 7.0 introduces a new feature, "flaky path reporting". this article is an attempt to explain how this feature really works and what can be expected.
Instructions
DELL EMC SW : PowerPath 7.0 (any platform)
PowerPath 7.0 introduces a new feature, "flaky path reporting". The "installation and administration guide" mention the following :
Flaky Path Reporting to PowerMax Overview
PowerPath already can identify paths with intermittent IO failures (also known as flaky paths) and mark them as autostandby io-per-failure (asb:iopf) automatically.
When paths are marked as autostandby, they are not used for IOs and hence performance issues can be avoided until the issues with those paths are fixed.
For devices from PowerMax running microcode 5978.444.444 and above, PowerPath also reports flaky path information to the array.
This process helps array administrators to identify potential problems on the array if multiple hosts report flaky paths from the same port.
The purpose of the feature :
This feature is an enhancement to the existing Flaky path Reporting functionality that has been in previous releases of PowerPath product for the last number of years.
The aim of this enhancement feature is to help Customer Service identify a problem before the customer is even aware of it via the array dial-home facility and ideally be able to report to the customer which HBA/FA pair the issue exists with.
Implementation :
- PowerPath determines a path is flaky and reports the path details to the array (and locally marks the path asb:iopf)
- The array stores the HBA WWN/FA port/Host Registration Index value/Timestamp in a table that can store two entries per physical port
- Every 24 hours, PowerPath re-tests the path to see whether the previously reported flaky path is still flaky
- If the array is notified within 25 hours that the flaky path is still flaky, the array dials home with the appropriate error details.
- On the array itself, the error is logged once every 9 hours per director.