What is spinning my disks?

Ok AmberV and you other mac gurus, 'splain this one to me.

I have my array plugged into the MBP. Everything works wonderfully. The wife and kids leave and I am left in a warm, bright place with no noise. Just the glow of the LCD and the smell of 8 hour old coffee. Heaven. All the sudden my array (which is idle) spins up. There is no backup running, no svn, nothing. I go into spotlight and find that the drive is excluded from indexing. Then I hear the drive spin down.

I happen to have a meeting at 10. As I am dialing into the call the drive spins up. Too busy on the call to look into it I decide to wait until I am done. At 10:30 I hear is spin up again. I check systems logs and NOTHING is happening at that time. Cron shows nothing, same for at. Thinking the sky may fall and I need to rip a drive out, a sudden flash of lucidity and I say “hey, what about the smaller drive? does it do this too?” IT DOES!!

So both drives are removed from spotlight, there is not indexer running (that I installed), no cron, no at, no recorded activity that is every 30 minutes. Any ideas?

The Mrs indicates that this is normal as I often leave the house with the arrays plugged in. Apparently it drives her nuts as the LaCie is pretty noisy. The only explanation for me not noticing is that there is normally a bit of noise.

Any ideas?

I don’t know off the top of my head, but have you tried disabling the Spotlight daemons for a bit and see if it stops? It might be that even though the drives are not listed as indexed, when the process wakes up it wakes up the devices to get volume and partition identities from them.


I have two La Cie external drives, and they are so noisy that I only turn them on when making nightly backups. Earlier models used to spin down when not in use; these just roar along all the time, even when I put my iMac to sleep. When I asked LaCie about the problem, they blamed it on Apple, of course.

The other and grimmer possibility is that your drives are beginning to fail. I hope not.

If your work routines will allow, I recommend dismounting and then manual shut down. When you turn them on again, they should auto-mount.


hmm… If my memory serves me right, the .plist file that stops Spotlight from indexing a drive is stored on the drive. Can you temporally kill the spotlight process to make sure that this isn’t the cause of your problem?

launchtl remove com.apple.Spotlight

Spotlight is dead. Let’s see how it goes. 15 minutes should answer the question.

Drive didn’t spin down until 3:01, then spun up at 3:02.



Why don’t you try starting up in safe boot mode to disable everything but essentials and see what happens?

Press the power button. Immediately after you hear the startup tone, hold the Shift key. The Shift key should be held as soon as possible after the startup tone but not before. Release the Shift key when you see the gray Apple icon and the progress indicator (looks like a spinning gear).

It takes longer to startup this way, by the way, and also conveniently clears caches and other things (according to Enterprise support).


The sound of my hand making rapid forceful contact with my forehead may be audible where ever you are located. If you put your head out a window now and listen closely you might hear it.

Once I get to a point I can shutdown (about an hour from now) I will give this a shot.


It didn’t spin down for 35 minutes. Then it stayed down. Must be something I have running that I am not recognizing.

I think you may find it’s nothing serious at all, probably just mdworker which deals with meta data etc. It doesn’t appear to have a set time when it goes to work, though usually after you have been altering or working with documents.

Sounds to me, like Hillbilly`s been at the shine again!!

Well a few things.

(1) VM is using the disk as a source and is paging.

(2) the more obvious is the hardware is actually “sensed” every so often. The actual hardware sends a signal to see if a “response” is given for any new changes in state or to check if the hardware is still connected and operating. This “pulse” that is sent to a drive or device can at times “wake up” the hardware from a dormant state. It does not wake up fully in most cases but kinda “nudges” the hardware enough to elicit a response so the system knows the system is still active.

Many new hardware devices have the internal ability to “spin down” when not being accessed. Like an energy saver BUT when the system has to do its check to see if the hardware is still there and not turned off the pulse it sends may wake this device up just enough for the device to reply "Hi Im still here and working. I am not disconnected gut rather in just a suspended animation or spun down mode.

Ok why is this a “new” symptom and varies from machine? Simple. Different hardware makers have different methods of spin down or “wake up” responses but on average most of the more modern hardware contains all the new energy saving features that save energy and prolong life. On a hardware level they can spin down or going into a semi “hybernate” mode until accessed. When accessed they “spin up” to full operational level. But when the system does its hardware checks to make sure these devices are not disconnected they “pulse” the hardware to see if a response is forthcoming. If the system hardware gets a response it knows that even though the device appears to no longer be there “sleeping” it is actually there and still connected. Very common for USB or FIrewire because how would the system know if you disconnected a device if you just “unplugged” the connection? Simple. When it pulses the devices every so often if no response is given then there is no device. Because the newer hardware has such energy savings features the pulses wake up the device and when all is quiet you realize that even though nothing on the operating system is running a process that would cause this random devices spin up (even internal devices) at random times it seems. Usually after you have not accessed the said device for a little time (giving the device enough idle time to go “sleep”.

Its all on a hardware level instead of software hence the OS has no clue of the process. It only has data of the result (Pulse reponse = hardware still there and active).