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macrumors 68000
Original poster
Mar 4, 2022
United States
As you may know, I use two machines primarily, an M1 MacBook Air and a 5,1 Mac Pro, both for different things. However, on the 5,1, I'm having a strange issue with my SanDisk Extreme 1 TB SSD specifically, where as soon as I wake the machine up from sleep, it throws a flood of "Disk Not Ejected Properly" errors. One time, I think I had 20 of them. What's so weird though is that it only happens with that specific drive, and only on this machine; this does NOT happen with my M1 MacBook Air. Also, I should add that the SanDisk is APFS-formatted with two volumes, has 330 GB of free storage (so plenty), and is hooked up to one of two USB type C ports on my USB 3.0 PCI-e card. Plugging it into the type A ports on the card does not fix the issue. And naturally, this has to happen with the drive I house ALL my active projects and sample libraries on, so I can't really wipe it...

Any ideas why this is happening? I've not tested it with any other macOS versions, so it could very well be an issue with this installation. But it also could be an issue with the drive (which I don't think it is) or with the USB 3.0 card.

EDIT: Also, it appears that the SanDisk is pretty warm when plugged into the card compared to plugged into my M1. Could either be because (not limited to these obviously):
  • For some reason it's wasting read/write cycles on the SSD for no reason, and filling up the cache (but that doesn't make any sense because the free space is still the same), or
  • The hot air coming out the back of the 5,1 from the CPU and GPU (probably what it is)
When plugged into the MBA, it runs nice and cool (except when copying large amounts of data obviously)
Last edited:


macrumors 68000
Jul 29, 2011
This is a common issue with add-on USB cards in the Mac Pro. When the Mac Pro sleeps it is cutting power to the PCIe slots (and thus your USB 3 card). When the card loses power, your SSD unmounts. The Mac is probably waking up periodically (check the "Wake for Network Access" setting in Energy saver preferences), causing the USB card to begin receiving power and thus reconnecting your SSD drive. Shortly thereafter the Mac goes back to sleep and the process starts all over again.

Possible solutions:
  • Disable sleep
  • Settle for connecting your SSD to one of the built-in USB 2.0 ports, which don't lose power during sleep
  • Use an app like Jettison to automatically eject your SSD prior to the onset of sleep mode
Edit: You should know that despite the annoyance of those messages, it is extremely unlikely that any harm is coming to your SSD or the data stored on it. A sleep event on any Mac triggers flushing of caches and finishing write and read operations, so it's a very "safe" time for any disk to be ejected. So if you can put up with dismissing the error messages then you can simply continue using the SSD just as you have been without much worry (that said, SSDs just like HDDs can fail at any time, so any important data should be backed up as a matter of course).

To avoid the multiple disconnection notifications, uncheck the "Wake for network access" in energy saver preferences.
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