On 06/30/2014 03:52 PM, Andras Horvath wrote:
> Actually the drive has its own power so it is not USB powered. I 
> cannot tell if the drive spins down (did not get the idea to check 
> it), but the CPU is in 100% I/O wait all the time after this happens. 
> I was told the disk is a WD RED, but I'll check the power mode later 
> with hdparm.

The only time I've personally run into the 100% I/O wait issue with EL6 
was when I was trying to RAID a Seagate 1.5TB internal SATA drive with a 
WD GREEN 1.5TB SATA drive.  The system was basically unusable, with 
frequent and long forays into 100% iowait territory. Replacing the WD 
GREEN drive with another 1.5TB Seagate fixed that. It could be WD's 
TLER/non-TLER (Time-Limited Error Recovery) handling doing this.  More 
info on this at http://www.wdc.com/en/library/other/2579-001098.pdf and 
googling 'WD TLER' yields a lot of hits.

Another possibility is that the idle timer is set up on the disk; I 
would think that it would hit you sooner, though, if it was that issue.  
I ran into that sort of issue with an eSATA Seagate a long time ago, 
where throughput was good but after a while it would error out.  For 
some reason the standard Linux write caching and the timeout interacted 
badly.  There's more about the WD RED and GREEN drives and this idle 
timer at 
http://forums.freenas.org/index.php?threads/hacking-wd-greens-and-reds-with-wdidle3-exe.18171/ 
with some open source tool at http://idle3-tools.sourceforge.net/

> Thank You for the suggestions. Andras 
You're quite welcome.