HP A3550A - High Availability Disk Arrays Model 20 Storage Enclosure User Manual page 246

Note It is important to be aware of the distinction between the occurrence of a failure and the
reporting of that failure.
A disk array component failure is reported immediately to the disk array. The disk array,
in turn, notifies the system of this event when the next I/O is attempted to any disk array
component . It is important to recognize the following:
• The next I/O may or may not occur soon after the failure occurs.
• The component on which the I/O is being attempted at that time
may or may not be the failing component.
• In a multi-host configuration, the system attempting the next I/O
may or may not be the system that was using the disk array
before or during the failure.
Note Always check that the FAULT, REPLACE, or SERVICE LED on a suspected failing
module is lit before removing it.
5-74 High Availability Array Monitor (HARAYMON)