External HDD – is Spotlight indexing really off?

At home my MBP’s usually hooked up to an external HDD for TM backups. I have added that disk to Spotlight’s Privacy list and it does show up there whenever I plug the disk in.

But lately I’ve noticed lots of HDD activity even when TM is not backing up. I see CPU load go up a bit too and the culprit is usually one or several (more commonly) instances of mdworker. That to me indicates Spotlight is still indexing (or attempting to) my external HDD which holds just my TM backups.

I’ve tried removing the HDD from Spotlight’s Privacy list and adding it again. No difference. I should note I have the exact same setup at work and there I don’t think I observe similar behavior.

Any idea how to check if the HDD is really not being indexed? And if it isn’t, what’s up with all the disk activity and mdworker load outside of regular hourly TM backups?

I believe if you show invisible files and folders and check the root level of that HDD there should not be a “.Spotlight-V100” folder if it’s not being indexed.

There sure was that folder at the root of the disk. A sudo rm -r took care of it. But now I wonder how to maintain that no new indexing happens considering that this index was created even though none should have been with the HDD on the ignore list…

I think this still works…

Assuming you will never boot from this drive, use the Terminal app and this command:

touch /Volumes/{NameOfDrive}/.metadata_never_index


I found this in the book “Take Control of Backing up your Mac (3.1)” by Joe Kissell. This seems to explain why the indexing was happening even with your Time Machine disk on the Privacy list.

“Spotlight always maintains an index of your Time Machine disk so you can search in your backups. You may be tempted to prevent Spotlight from indexing that disk by adding it to the Privacy list in System Preferences > Spotlight, but don’t bother. It doesn’t work; Spotlight keeps indexing your Time Machine disk even if it’s on the list. But this is nothing to worry about, because Spotlight searches don’t normally display matching items on your Time Machine disk except when you’re on the Time Machine screen.”

Excerpt From: Joe Kissell. “Take Control of Backing Up Your Mac (3.1).” iBooks.


That’s most interesting. Thanks, Dana. :slight_smile:

Sorry, I completely missed what you said about it being a TM drive.

Yes, it is perfectly normal for it to be indexing. There is no requirement for it to be added to your Privacy list and nothing you can do to prevent it.

Obviously, it would be of lesser impact if you left it connected all the time, both in terms of catching up on backups and if what you are observing is Spotlight related.