What are these processes and how do I prevent them?

Question

For many years, many have complained of external drives that are in standby/sleep spinning up for no apparent reason.  From the user's point of view this is unnecesssary, but to make matters worse, the system usually stops everything else while waiting for the drives.
I have a Mac mini that I use as a home theater pc.  The media and backups are on a 5-bay enclosure (no RAID) attached by USB.  While watching a video, the unused drives will go into standby mode, which is good.  But then, with no user activity, they will spin up, freezing the video and everything else, which is not good.  As these are slow drives and spin up sequentially, this can take 10-20 seconds.  This may happen once or twice an hour, but sometimes more frequently.
In looking into the causes, I have turned off time Machine (after putting these drives into the Privacy section for good measure).  I also prevented Spotlight and fsevents logging with the following:
mdutil -i off /Volumes/<drive1> /Volumes/<drive2> . . .
cd /Volumes/<drive1 and then repeat for other drives>
     rm -rf .fseventsd .Spotlight-*
     mkdir .fseventsd
     touch .fseventsd/no_log .metadata_never_index
As far as I can tell this has worked to stop those processes from accessing the drives after they are mounted, but the problem persists.  To find out what else might be causing them to wake up:
sudo fs_usage -w | grep -e Volumes/<drive1> -e /Volumes/<drive2> . . .
and here is what I found last night (actually didn't use the -w last night, thus it is cut off):
18:35:36  fsgetpath   /Volumes/XBMC         0.000026   SSDragHelper
18:35:36  fsgetpath   /Volumes/Stuff        0.000006   SSDragHelper
18:35:36  fsgetpath   /Volumes/DatOptic_3   0.000005   SSDragHelper
18:35:36  fsgetpath   /Volumes/MacBackUp    0.000003   SSDragHelper
18:36:15  fsgetpath   /Volumes/XBMC         0.000026   System Prefe
18:36:15  fsgetpath   /Volumes/Stuff        0.000004   System Prefe
18:36:15  fsgetpath   /Volumes/DatOptic_3   0.000003   System Prefe
18:36:15  fsgetpath   /Volumes/MacBackUp    0.000003   System Prefe
18:55:36  fsgetpath   /Volumes/XBMC         0.000034   GoogleSoftwa
18:55:36  fsgetpath   /Volumes/Stuff        0.000004   GoogleSoftwa
18:55:36  fsgetpath   /Volumes/DatOptic_3   0.000003   GoogleSoftwa
18:55:36  fsgetpath   /Volumes/MacBackUp    0.000003   GoogleSoftwa
After looking into the Google process, I was surprised to find the tentacles that Google puts into your system, and ripped every bit of it out that I could.  But I have no idea about what's going on with SSDragHelper and System Prefe (presumable System Preferences).  This must be OS X itself?  What are these processes doing, and is there any way to prevent them from accessing these disks in this way?

Answer 1

Thanks for the reply Hen3ry.  Looks like you've done a lot of investigation.  For me, fs_usage entries accompanying spindown are not problems - I'm happy if the drives spin down.  My problem is the spinups.  But still, I don't think it is necessary to time the fs_usage entries with spinups.  If you grep for the drives you're concerned about, you will see any process that would potentially wake them up.
Because my understanding is limited, I also am more concerned with the process/application that is accessing the drives than with the functions or commands they are sending.  And the values that are returned by those functions are way beyond what I can deal with.
It's interesting that you've found a difference between your old and new drives.  Could you specify the enclosure and drives in each case?
The StorageStatus app looks interesting; thanks for the tip.
Here's a summary of what I've done so far, which I think is working.  I need a few more weeks to know for sure.
How to prevent unwanted drive spin-ups
If you are actively using the computer that the enclosure is attached to, nothing on God’s green earth will stop OS X from waking them up after some user action, even ones that seem to have nothing to do with the external drives.  But if you leave the computer alone while some application is running, like watching a movie or downloading a file, you have a fighting chance of coaxing OS X into leaving the uninvolved drives alone.
If the drives are shared with any other computers over a network, eject them on those computers
Otherwise, OS X (AppleFileServer) will poll them every 10 seconds.  This might not be bad if you want to just keep the drives spinning and the other computer stays awake.
Third-party apps
Make sure no apps are running that might access your drives.  Google runs some processes that do this (maybe I’m naïve, but I was so shocked I removed chrome and every other trace of Google from my Mac mini system). Another is iStat and any utility that monitors SMART status in the background.
Don’t let Spotlight index or search the drives
Spotlight is persistent, and it may be necessary to take a variety of steps to stop its various processes (mds, mdworker) from accessing the drives and waking them up.  In other words, kill it, drive a stake through its heart, then burn the body:
In System Preferences > Spotlight, add the drives to the Privacy pane.
Add a file called .metadata_never_index to the root of each drive (note the leading period).  The easiest way to do this is in Terminal
touch /Volumes/<drive1>/.metadata_never_index
Tell Spotlight AGAIN to keep away from the drive:
mdutil -i off /Volumes/<drive1> /Volumes/<drive2> . . .
Finally delete the Spotlight folder from the drive.
rm -rf /Volumes/<drive1>.Spotlight-*
Stop fseventsd from logging in the drive
This is easy, just putting a no_log file in its folder.  I have found that rarely it still writes some files in there, but it doesn’t seem to do so when it causes problems, so . . .
          rm –rf /Volumes/<drive1>/.fseventsd/*
     touch /Volumes/<drive1>/.fseventsd/no_log
Finder sidebar
Some people say that if the drives show in the Sidebar of Finder windows, the Finder will be checking them.  I’m not sure. But to be safe, in Finder Preferences > Sidebar, uncheck External Disks.
Just say no to Time Machine
On the home theater mac itself, regular backups shouldn’t be needed.  You should be able to just turn Time Machine off.  However, it is probably sufficient to simply open System Preferences > Time Machine > Options and add the drives to the list of locations to exclude from backup.
Second, local backups can be disabled with
sudo tmutil disablelocal
Look for other culprits
If the problem persists, use fs_usage, which generates a real-time log of filesystem activity. There is so much going on that you need to use grep to restrict the output to entries that involve your drives. The entries that accompany your drive spin-ups are the ones you really want.
sudo fs_usage -w | grep -e Volumes/<drive1> -e /Volumes/<drive2> . . .
Now leave the keyboard and mouse alone, as many things you might do will cause the drives to be accessed. You probably want to find what does it when you’re not actively interacting with the computer.  It’s not really necessary to wait for your drives to sleep and see what wakes them.  Any activity you see would probably wake the drives if they were asleep.  When you see some activity and want to stop and examine, type Control-C to stop the output.  On the far right of each entry is the process or application that accessed the disks.
I got pointers from http://system-log.tyr.org.uk/2012/01/31/how-to-stop-usb-drives-from-spinning-up- unnecessarily-on-os-x-lion/ and http://www.jackenhack.com/disk-that-refuses-to-sleep-in-mac-os-x-how-to-fix-it/