It's early days yet, but if you rely on vendors' software for your RAID enclosure, you probably need to find out what their macOS 27 plans are.

We've had macOS 27 for all of four days at this point, and there may already be a show-stopping problem for folks that hang on to RAID enclosures. We've found several that just don't work under macOS 27.

For example, I've got a Thunderbolt 3 LaCie 12Big enclosure that I've had for a while. It runs fine in Tahoe, on a Mac mini home server that I've had for years.

That LaCie 12Big doesn't work at all in macOS 27. I've tried fresh installs of the software, different cabling, updating a Mac in place that it worked on in macOS 26, nothing works.

All of my dumb enclosures work and mount fine. SoftRAID as it stands now from OWC works fine in macOS 27 to set up a new array on those dumb enclosures.

This has happened before, of course. Talk to Drobo and Pegasus enclosure owners about when Apple changed how it handled device drivers a few years ago. It's just worth mentioning that it's happening again.

To get in front of this, I'm not talking about RAID arrays with DIP switches, other physical ways to configure the drives, arrays set up with Disk Utility, or Network Attached Storage devices. This is about vendors that sell enclosures that need special software to run on macOS.

Who's at fault, and why is this happening?

I wish I had a good answer for you. Apple does like changing things, like how it's done something with the boot selector in macOS 27. So there's something there.

Also, macOS 27 also ships with no Intel code remaining, which could affect drivers compiled for Intel-only targets.. That may have something to do with it too.

Beta cycles are intended for developers to update their software to the new macOS. They exist for testing things like this.

But in our experience in the past, some things made by third party vendors get left behind.

Our advice as always stands. If you have mission critical hardware, this is not the time to try out the betas. And, if you've got enclosures that rely on older software, like my LaCie 12Big, it's time to contact the vendor to see what's going on.

And come up with a plan if there won't be support in macOS 27.