Prevent External Drives from Sleeping

Maybe not a good solution, but I can add my successful experience, starting with some older LaCie enclosures with Seagate Disks. There were two problems, possibly related to each other:

1) Disks started to sleep (irrespective of poset parameters and system preferences) and I had to wait quite some time to access the discs afterwards. This seems to be your problem.

2) Disks were unexpectedly ejected from time to time (was described on LaCie website, too).

Now with a new Mac mini 2023 I was so frustrated that I finally bought two new USB-C enclosures (which made the access to the discs faster!) and formatted the discs with APFS. And both problems disappeared!

I did not realize any performance problems with APFS on these old discs (Seagate Barracuda 7200.14 AF with SATA 3.1, 6 Gb/s). And I think the fact that Time Machine decided to use APFS on an erased disc tells us that APFS is OK for HDD today.

I must admit that sometimes I thought that one of the discs still slept, but there was no delay to access the contents. No problems left at a reasonable cost and improved performance.

Terminal:

sudo pmset -a disksleep 0

Worked for me. The -a means ALL so covers everything. 0 means zero minutes so NEVER. I actually changed the 0 to 30 (minutes) for me as I do want drives to take a break if not being used.

My attached APFS drives were fine. The issue was with my 2 Sabrent 5 HDD drive enclosures connected via Thunderbolt/USB4. At times I have all ten drives mounted - and it was ridiculous with the constant barrage of spinning down, spinning up over and over.

Whoever posted the Terminal command - many thanks!!

Mac Studio 2023 M2 Max Sonoma 14.2.1

larry666 wrote:

Why would this work when system settings doesn't?

System Setting only loads once the Operating System is loaded.

pmset runs even before the Operating System loads

pmset -g shows disksleep is already at 0 …

I rarely use Terminal but, however, sudo pmset -a disksleep 0, which I think is correct to stop all disks from sleeping, seems to have worked …

Good and welcome

Am pleased the suggestion may have solved this issue or at least was helpful.

Use the Terminal command

man pmset

Excerpt from above command

SETTINGS

    disksleep - disk spindown timer; replaces 'spindown' argument

     (value in minutes, or 0 to disable)

larry666 wrote:

"This 3.5 Hard Drive Case will switch to sleep mode automatically without operation in 3mins".

Many drives' and enclosures' have a built-in sleep function. The setting in macOS, "Put hard drives to sleep when possible", does not prevent a drive from sleeping when disabled.

larry666 wrote:

But the external HDDs are going to sleep after System Settings has loaded …?

Seems I spoke too soon - HDDs went to sleep again.

I guess this is to do with the way Seagate is managing the drives?

Unless I and reading the tea leaves wrong - who or what is Managing the Seagate drive ?

macOS, for a very long time does Not Require Seagate ( Third Party Drive Management Software ) or any Third Party Software to Manage External Drive

Back to me last comment, any reason not to put the drives back to APFS when this doesn't happen?

Sorry do not use NAS configurations in any of my 3 different machines setups

Too iffy and complicated for my liking

Use TM Backup to dedicated drives and adjunct CCC also to dedicated drives

All directly connected to each of the 3 machines