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Disks Ejecting While In Use

Has your Mac OS warned you that a volume was not ejected properly even when you know it’s still attached?

Have you been warned by the SoftRAID Monitor that there is a problem with your Mac?

If so, you may have encountered a problem which affects disks attached via the Thunderbolt bus.
This problem causes older Mac OS X versions (prior to 10.12.2) to think a disk is no longer attached even when it is still plugged in.

Upgrade to macOS 10.12.2 or later
We now know that a problem in the macOS system software is the cause of disks ejecting while in use. This problem is fixed from macOS 10.12.2 onwards.
We strongly recommend that you upgrade to macOS 10.12.2 or any later macOS version if you have encountered this problem. If you are unable to upgrade, you can use the instructions which prevent the problem in most, but not all, configurations.

After upgrading to macOS 10.12.2 or later, you can re-enable sleep on your Mac. You can also enable the “Put hard disks to sleep when possible” setting in the Energy Saver panel of System Preferences.

Important Note: If you have upgraded to macOS 10.12.2 or later and your disks are still being ejected while in use, we want to hear from you. Please collect a SoftRAID Tech Support Report and send it to our support engineers ( so we can determine if it is a new problem.

We have been working with Apple engineers for over 2 years, investigating and fixing bugs in Thunderbolt, and will continue to do so in the years ahead. It is due to this close relationship that the original problem with disks ejecting while in use was fixed in macOS 10.12.2.

How to prevent this problem in older versions of Mac OS
Turn off sleep in System Preferences:

1. Go to the Energy Saver panel of System Preferences.
2. Uncheck “Put hard disks to sleep…” (see image below)
3. Ensure that ‘Prevent computer from sleeping…’ is checked (see image below)

We’ve discovered that, for the majority of users, this solution prevents the ‘disk ejecting while in use’ problem.

What is actually happening on my Mac when the disks ‘disappear’?
We don’t have access to the drivers which control the Thunderbolt interface on the Mac. However, every time the SoftRAID.log file shows disks disappearing, the Mac system log shows entries from a second or two before this which indicate the PCI configuration is changing.

Is this a problem with a faulty Thunderbolt enclosure, bad cable, or unreliable disks?
We have had customers replace their ThunderBay enclosure, use different brand Thunderbolt cables, change disks and change power supplies. None of these actions have prevented this problem from occurring.

Does this problem only happen with OWC ThunderBay enclosures?
No—our customers have encountered this problem with the following enclosures: LaCie 5Big, OWC ThunderBay IV, ThunderBay 4, and ThunderBay minis. If you have experienced this problem with a different enclosure, please via the instructions at the bottom of this page.

Is this problem caused by SoftRAID?
No. Customers have been able to reproduce this issue after uninstalling both SoftRAID and the SoftRAID driver. After uninstalling SoftRAID, they created 4 separate volumes with Disk Utility (one on each of the disks in their Thunderbolt enclosure). They then saw that these volumes were also ejected while in use, thereby confirming SoftRAID does not cause the problem.

How many people are affected by this problem?
Our current estimate is approximately 1 in 1,000 users experience this problem, at a frequency between once every 6 hours to once a year.

Solutions we have tried
We have asked customers to replace their Thunderbolt enclosure[s], purchase new Apple thunderbolt cables, purchase new drives from a different vendor and reinstall their copy of Mac OS X. We have also had them clean the connectors on the Thunderbolt ports & cables with alcohol and cleanroom-grade cotton swabs. None of these actions have fixed this problem.

How can I fix this problem?
The current fix is to ensure you are using macOS 10.12.2 or later, since Apple has fixed the bug in 10.12.2. Or replace your Mac—using a different Mac (it can even be the exact model and configuration), stops the problem happening. If you can’t upgrade, and using another Mac is not possible, see next item for a workaround.

How can I work around this problem?
If you don’t have the luxury of using a different computer, you can work around this problem by disabling sleep in the Energy Saver panel of System Preferences. This fix works more than 95% of the time.

Are you still investigating this issue?
Yes, we are actively investigating this issue, and will continue until we have a better understanding of both the root cause and how it can reliably be prevented from happening to all of our customers.

Need more help?
If you have additional questions, you can email them to our support engineers ( Please make sure you send a Tech Support Report with your question so we can investigate your configuration.