mcclnx mcc wrote: > 1. is this disk really "degrade" or not? Depends on your point of view, to me it would be. I remember two situations with "predictive" failure on HP Smart arrays a few years ago where the drives were practically dead but the controller kept using them dragging performance down something like 90%. The drives were detected as about to fail but there was no way to remove/disable the disk from the array remotely, so we had to send someone on site to yank the disk to force the array to rebuild. HP later said a firmware update should fix the issue, never got around to upgrading it before we migrated off those systems onto a real SAN. > 2. how O.S. can predicate disk going to failure? In this case it's not the OS, it's the controller that is keeping track of a bunch of internal counters on the disk and perhaps even scrubbing it every so often. If # of soft errors exceeds a threshold it triggers the predictive failure logic. > 3. do I need replace this disk now? Based on my past experience yes, and any enterprise storage array's support contract(for comparison) will trigger an immediate replacement if the array detects that condition. nate