Why does the hard drive light blink once per second?

Question

I recently purchased a 1 TB Seagate ST31000528AS drive and I have Windows 7 RC (build 7100 installed on it). I've noticed that whenever the computer is idling, the hard drive light tends to blink at a rate of about once per second. What are the possible reasons for this?

As far as I can tell there should be no disk activity (all non-essential services are switched off and if there's some amount of swapping going on, then I would assume the drive activity would be a little more erratic that that.

At the same time I've installed drive activity monitoring software but it doesn't blink at the rate of 1 per second. So I'm inclined to believe that there's really no read-write activity taking place.

Bottom line..what's with the blinking lights?

Answer 1

While this doesn't pertain to your exact drive model, this Seagate knowledge base article implies that a slowly blinking light means the drive is in power save mode. This would make sense in your case, especially if you are seeing this during idle periods and no activity in the activity monitor.

Answer 2

There is a possibility that the problem is not your hard drive, but rather a SATA DVD / CD / Blu Ray drive. What is happening is that Windows continually pings the drive about once per second to see if there is any media in the drive so that it can start Autorun. You can test this by going into your device manager and disabling your CD drive. Disabling Autorun will also cause the light to stop blinking. For practicality sake, you'll probably just have to live with it.

Answer 3

This could also be due to Indexing pre-fetching and the like. If you would like to see exactly whats writing to the disk you can also use a program like Process Monitor.

http://technet.microsoft.com/en-us/sysinternals/bb896645.aspx

Didn't notice the non essential services switched off part. The process monitor may still help though.