Stop HDD's unmounting when display sleeps?

I’ve tried all sorts of googling on this and can’t find the right results so I’m hoping I can get some help here :slight_smile:

Situaiton - I have a M1 Pro MBP in clamshell mode connected to a OWC Thunderbolt 3 Hub and an Apple Studio Display.

I have an SSD attached to the Display for Time Machine and two HDD’s attached to the OWC Hub running as a JBOD under Mac OS. I also have another HDD connected to the Hub for general storage.

Whenever my Mac puts the Studio display to sleep all my drives unmount (cleanly), and remount when the display is woken up.

I run SyncThing on my MBP to keep some folders from my NAS synced to the JOBOD on the mac (so I can leverage Backblaze) so I want these drives to keep working while the display is off. I’d also like TimeMachine to run while the display is off.

I have the Mac power settings as shown below but I can’t stop these drives unmounting.

Any ideas on how to keep these drives connected and fucntional while the display is off?

1 Like

Hmmm… That seems a bit weird to me. I have a Mini with a bunch of external drives that don’t unmount when the display goes to sleep. Are you sure the machine itself isn’t going to sleep?

(The Mini is a home server. Its predecessors were older Mac laptops and I don’t recall this being a problem with them either, but I’d have to test to be sure.)

I can’t be sure it isn’t, but acording to my settings it shouldn’t be. If I set ‘Turn Display off on power adapter when inactive’ to a couple of minutes I can reliably reproduce the problem as soon as the display goes off, but the machine should not be sleeping at this point.

My ‘Sleep’ settings may be a little mixed up on my MBP, for example the ‘Sleep’ option in the main mac menu is greyed out and unelectable, and has been for a while.

I have a recently re-formatted M1 MBA on hand, so I will test with that and see if I get the same behaviour.

Since you have another computer maybe try pinging your MBP from the Air when the display is asleep. If it doesn’t answer then it’s also asleep.

1 Like

Perhaps run “pmset -g live” in a terminal window to see if there is anything wonky with power management settings.

Thanks, I’ve run it on the MBP and on the MBA and see the following:

MBP (the problem machine):


I can see a flag on ‘Sleep Disabled’ on the MBP and a different value for hibernate mode.

I also did some testing with drives connected to the MBA and all the system preferences set the same as they had been on the MBP - it works fine on this machine. When the display sleeps the drives stay connected.

When the MBP display sleeps (and I experience the drive disconnect issue) I can still ping the MBP from another device on my LAN.

1 Like

I and some others have recommended using Sam Rowland’s Sleep Aid app Sleep Aid - Diagnose and solve Mac sleeping issues for its remarkable visualization of what a Mac is doing sleep-wise. Same underlying settings as what you reveal with the pmset command but perhaps an easier way to view and set useful values and log the results.

I also use St. Clair Soft’s Jettison app to tell my MacBook Air to NOT unmount the drive and share that I use for Time Machine backups (on the Options tab).