On 07/01/2014 01:29 PM, Andras Horvath wrote:
> On Mon, 30 Jun 2014 16:23:45 -0400
> Lamar Owen <[log in to unmask]> wrote:
>
>> 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/
> A note:
>
> hdparm -I /dev/sda | grep -i pow
>             *    Power Management feature set
>                  Power-Up In Standby feature set
>             *    SET_FEATURES required to spinup after power up
>             *    Host-initiated interface power management
>                  Device-initiated interface power management
>
> I cannot access the power levels through the USB interface. I'll check the eSATA connection tomorrow.
>
> I restarted copying again, and in a minute the CPU hung again with 100% I/O wait. The "iotop" output shows absolutely nothing, as if there was no load on the disks at all. Interrupt and context switch is around 20-50, so almost nothing (dstat output). Disk operation is zero. Load is at 5.01. The rsync processes that I'm using for the copy cannot be killed or force killed.
>
> Any idea? Thanks.
>
>
> Andras

Circling back around to the "is it spinning" question, for externals in 
a workable enclosure, I've found the "Jurassic Park" test to be rather 
trustworthy.[1]

Does dmesg report anything interesting?

Pat


[1] https://www.youtube.com/watch?v=1koa2xAxCAw

-- 
Pat Riehecky

Scientific Linux developer
http://www.scientificlinux.org/