Jordan Russell wrote:

On 6/16/2010 11:52 AM, Bill Davidsen wrote:
  

quoted

Alternatively, you can try setting your io scheduler to 
deadline,
    

Wow - huge difference! No "hung task" warnings, no processes stuck in
"D" state; the system remains completely responsive throughout the
entire check.

I don't see why, though, processes are blocking for 2+ minutes on the
simplest of I/O operations when the default CFQ scheduler is used. Isn't
CFQ supposed to distribute I/O bandwidth in a "completely fair" manner?
Do md checks bypass the fairness algorithm?

  

The CFQ has its own idea of what is "fair" and works poorly (even 
abysmally as you saw) for some load cases.

-- 
Bill Davidsen [off-list ref]
  "We can't solve today's problems by using the same thinking we
   used in creating them." - Einstein