USB exFAT Disk Access without cease (spotlight disabled)?

Is there any new features in Sierra that might scan the drive for any reason other than Spotlight?

Apple has upped the security game with Sierra. As you can imagine, this has "broken" a number of things and we see posts here with a common theme around upgrading to Sierra broke ...

One possible one is that with the release of Sierra, Apple enabled System Integrity Protection (SIP) by default. It was available with El Capitan, but unlike Sierra, it was NOT enabled by default.

Ref: About System Integrity Protection on your Mac - Apple Support

Take a look at that disk with mdutil…

https://developer.apple.com/legacy/library/documentation/Darwin/Reference/ManPag es/man1/mdutil.1.html

mdutil -s "/Volumes/[Disk-Name]"

/Volumes/[Disk-Name]:

Indexing and searching disabled.

Is that listed as disabled or enabled for indexing?

There are also command line options to disable & turn indexing off for a volume. Terminal may give you more feedback than the UI…

# turn indexing off…

mdutil -i off "/Volumes/[Disk-Name]"

# disable indexing…

mdutil -d "/Volumes/[Disk-Name]"

Also do you have permission to edit items at the base of the drive? Are you an admin when you disable the indexing in the UI?

You will need sudo for the above operations according to the last line of the short help

mdutil

…

NOTE: Run as owner for network homes, otherwise run as root.

I don't think Time Machine is related to Spotlight indexing because TM uses file system events to track changed files (fsevents). Exclude that disk if you use TM & reboot to see if the constant usage & indexing stops.

It is unclear to me why it would continue to get indexed. Did you try the option to erase & rebuild the index…

mdiutil -E "/Volumes/[Disk-name]"

I would do that in an attempt to purge any existing index & then disable it. At this stage it probably won't make any difference.

I would reboot into safe mode & see if it behaves the same there…

https://support.apple.com/en-us/HT201262

NOTE: many features will not work in safe mode just test as much as possible.

Reboot to go back to a regular OS.

Then I would consider making another exFAT volume on a USB thumb drive or other external disk to see if that behaves the same.

After that I would make a new Sierra install on another disk to check if a default Sierra is also indexing that disk.

You can also examine the logs in Console but I'm afraid I don't know what to look for specifically so that is best left until someone can direct you better. I'd poke around in the logs and connect the disk if you get really bored…

Typically, the external drive's firmware controls when the drive spins-down, not the computer's operating system.

I am aware of at least two issues using ExFAT-formatted drives with OS X since Yosemite:

1. Not properly un-mounting the drive can cause data corruption. This is actually true for both OS X and Windows devices.
2. Apple has gone through a number of SMB implementation with each release of OS X, and now, with macOS Sierra. These SMB versions do not necessarily correlate with the Windows counterparts and have been known to cause trouble. Regardless, this is more of an issue with network-shared drives as opposed to drives directly connected by USB.

Together these may be the culprit behind why are having some issues with doing so.

Per chance are you running any anti-virus apps on your Mac? An example would be Bitdefender that periodically scans both internal and external drives. Although, when completed, the drive access activity typically ends.

Maybe reviewing Activity Monitor may provide some clues on what may be running that could be accessing the drive?

This can be difficult to track down, but I'd start with Activity Monitor and select the Disk tab.

Choose the View menu > Active Processes. That should result in a manageably small enough list of potential culprits.

Reboot to be sure that nothing has stuck.

You can try this if you are familiar with using Terminal, enter this next line, change the name (keep inside quotes) & hit return…

lsof | grep "/Volumes/[NAME-OF-DISK]"

Replace [NAME-OF-DISK] with the relevant name of the external disk. That will list open files on that disk - see if it changes over time (if Spotlight is indexing it for example).

It will NOT list system processes that you are not privileged enough to see, you need to be logged in as an admin (your first user account is normally the admin) and add sudo to the start, e.g.

sudo lsof | grep "/Volumes/[NAME-OF-DISK]"

It will request your admin password & that will not be shown - enter it blind & then hit return to run again.

Post a few relevant lines if you need help with it.

Being naturally curious, I found that the mds_stores process was still running on one of my external USB drives even though I added this particular drive to the Spotlight Privacy tab. In this case the drive was one of my Time Machine backup destinations. I was still a bit surprised that Spotlight was still communicating with it although it doesn't appear that it was actually indexing it. There are at least three processes used by Spotlight: mds, mdsworker, & mds_stores. Only the last one was active on this drive.

Not sure if this has any direct relationship to your issue with a ExFAT drive, but it might.

Yes, the Spotlight indexing process is used by Time Machine, probably to maintain it's directory. Time Machine backups should be automatically excluded from being included from the Spotlight "Search" function, but you will still see the process being used periodically on that volume.