Causes of a Path Migration

There are two possible causes for a path migration:

• Software command. Software commands the two QPs or two EECs to perform a path migration. Some of the circumstances that might cause software to trigger a path migration are:

  - Load-balancing. After examining the various performance counters (see “Performance Management” on page 1019) throughout the fabric, software might trigger a path migration to ease traffic congestion in the fabric.
  
  

  - Excessive soft failures. Software may determine (by examining various performance counters) that a specific link or a switch or router is experiencing frequent soft (i.e., correctable) errors that indicate a possible imminent hard failure.
  
  

• Repetitive hardware failure. A repetitive hardware failure causes the two QPs or two EECs to automatically migrate to the alternate path.