Drive access lagging under Win7 unless running self-test

I just got a new Dell a few days ago with Win7.  The system has a WD5000AAKS-75V0A0 drive installed.  As I was using the system I noticed that it would “lag” or “hang” for a few seconds when I was typing or scrolling windows or doing whatever.  A bit of investigation led me to running Microsoft’s Resource Monitor where I could see that the Disk Response time on files would sometimes hit 1500 to 3000ms on a lightly loaded system. 

Further troubleshooting led me to run various tests and surface scans including the SMART long self test.  All the tests passed with flying colors.  What I noticed, however, is that while the drive is doing a self-test the lagging goes away.  It’s almost as if the drive is going to sleep under normal usage and taking a second or two to wake up.  But when doing a self test (or other surface scan) the access to files is MUCH faster, staying in the tens of milliseconds.  When the test is over the lagging returns.

It’s counter-intuitive in a way that loading the drive makes it perform better.

Dell has been no help in solving the problem thus far.

Is there something I can do to further diagnose the problem or some settings to disable the power management on this drive?  Having the system frequently pause for 1 to 3 seconds is driving me nutty!


I am having extreme lagging while transferring data from one drive onto this drive (WD15EADS).  I noticed the same issues you are reporting.  Response times on mine are varying from 1.5 to 21 seconds (YES, seconds, not milliseconds).  I witnessed a brief period of the 136GB transfer (38,250 files) where the response times dropped to subsecond responses.  If you find out anything more please let me know.  I am curious about the wdidle3 tool I’ve been reading about in various spots of the web.