macOS 27 does not support CoreStorage volumes | Hacker News Reader

macOS 27 does not support CoreStorage volumes

wadetregaskis.com

137 pointscolejohnson66112 comments

Well, heck.

I posted ~7 months ago about my decision to use HFS+ for backups, and had a couple skeptical replies. (https://news.ycombinator.com/item?id=47317123)

I guess I misjudged Apple's commitment to support HFS+ long-term.

It now seems like there's no real native way of doing encrypted backups to HDDs on macOS (APFS not really recommended for HDDs)... the options are either encrypted Time Machine to a network location, or a third-party tool.

Guess I'll figure out SuperDuper or Carbon Copy.

I don't think APFS was designed or tuned with HDDs in mind, but it will work just fine. Especially for backups where random read/write performance is not important.

I would not recommend using an APFS formatted HDD for Time Machine. It's painfully slow. With my Samsung T7 the hourly Time Machine backups are usually finished after a couple of minutes. Using my older HDD they can easily take 20 minutes to half an hour.

are you sure that is because of apfs? hdds are usually much slower, no?

It's definitely APFS. I've had the pleasure* of HFS+ and APFS on the same external HDD and APFS is horrible. Given it is optimised for solid-state drives[0], it's understandable there'd be some slack but it is absolute horse paste.

(If I could create an encrypted external HFS+ volume, I would but macOS hasn't allowed that for a while as far as my experience goes - it's non-encrypted HFS+ or encrypted APFS.)

[0] https://support.apple.com/en-gb/guide/security/seca6147599e/...

My point is that while the old HFS+ based Time Machine was performing ok on spinning disks, the new APFS based TM backups are excruciatingly slow and take ages to finish. I did actually compare both types on the same hard drive and even then the difference was very obvious.

While time machine used to be snappy on HDD it was build out of one of the weirdest little hacks hard links in folders. The new Time Machine might front a similar front end but under the hood its a different beast. You're having to mount snapshots as you move through time.

Can you use OpenZFS?

https://www.openzfsonosx.org/

MacOS is only Posix like, and does a lot of weird nonstandard things in the background regarding mounting drives/images.

There are restrictions on where things can run, what can run, and what is accessible to the process.

SSHFS is slow, but at least can mount windows/linux/android systems over VPN without issues. Look at what is needed to bring up SSHFS or NTFS support, and you should have a better idea of Apples walled garden policies.

Apple makes information appliances, and not general-purpose computers. Some may disagree, but they usually choose an exception use-case rather than the normal experience of users. =3

https://rclone.org/install/

I could, but I don't want to make my wife figure that out if I get hit by a bus.

I had to cmd+f "FUSE" all over the place first, thank goodness 0 matches

They are working on a userspace port, since newer versions of macOS don't/won't allow third-party kernel code ("kexts"). But it's based on Apple's newer FSKit API directly, not macFUSE or FUSE-T.

I just remember Google macfuse, osxfuse, then the new non-Google macfuse never working right for one reason or another. Don't think it was even a kernel vs userspace issue, it's just that the project kept changing ownership and getting broken by OS updates for other reasons, and it was confusing to find help because of the naming.

> encrypted Time Machine to a network location

this has a bonus feature where it will slowly corrupt itself over time and offer to start a completely new backup instead.

Sometimes it's pretty quick.

That would happen around once a year when I used the 2013 AirPort Time Capsule.

It seemed to stop killing itself when I moved to a ZFS backed samba share.

Funnily enough I also kept snapshots enabled because I was expecting TM to bork itself eventually, so I could always rollback to a working state but I don’t remember needing to use that.

Eh, mine was always on zfs first on FreeNAS then Ubuntu and it didn't seem to help.

The only thing that definitely made it worse was smb over openvpn. It'd corrupt itself every couple months instead of once or twice a year.

I also had a recurring corruption issue using a Windows Server file share.

Before MacOS 27, I was always able to remove the Time Machine destination, replace the corrupted sparse bundle with a fresh empty one, and reconfigure that as the new TM destination. I even made a script for this, so I didn’t have to figure out the terminal commands every time.

Unfortunately the script doesn’t work anymore; it throws ‘error 25’ on my MacOS 27.

What’s weirdest is that, before the corruption, TM backup and restore used to work fine on my MacOS 27. Seemingly the backup functionality works as normal, but setting the TM destination was broken.

I backup to TrueNAS which configures Samba/ZFS to take a snapshot before each backup. If TM decides to corrupt a backup, I can revert to a snapshot. I've only ever had to do this once in years of operation with several Macs backing up (each to their own share).

to go forward, you must backup

Ok I may be an idiot, but I just have a permanently attached external disk that does Time Machine, what am I missing out on? Why network location? Or are you backing up massive amounts of data? (for me it’s just 2TB)

Oh right — I could do a local HFS+ non-encrypted disk with encrypted Time Machine (I assume) — that just slipped my mind.

I switched to Borg on Linux server from local attached Time Machine disk after once I went to a long trip and forgot the disk at home.

It's mainly for multiple people in a household to back up to one location, especially if some have laptops that are often not on desks. Those Airport APs used to also let you attach disks for this. You could even do it over a VPN.

I so miss these Airport APs, I really don’t understand why the product line was cancelled, it was perfect.

Same, I still have one for random purposes. Still the easiest and most polished router/AP, has lots of features.

This is what I do. It's the happy path and works well.

It seems most of the problems with Time Machine happen when you try and run it over SMB. It's not that surprising when you realise what it is doing under that scenario. It creates a virtual disk on the remote and then formats it with APFS. You don't need much to go wrong to corrupt the backup in this scenario.

> I guess I misjudged Apple's commitment to support HFS+ long-term.

One thing I have learned with (current) Apple is to never trust their commitment to support something they're not using. And even be wary for stuff they are using. (in my mind, a core technical difference between Microsoft & Apple is that MS will bend over backwards for backwards compatibility, whereas Apple will drop it as soon as they can, and sometimes sooner still)

They replaced their use of HFS+ with APFS in 2017, so it's had a good run.

I have heard from ex-CoreOS (the Apple org) colleagues is that the organization is run intentionally lean, because the leadership believes that people do their best work under pressure. This leads, among other things, to aggressive YAGNI pruning.

sorry for the non-substantive nit. because we all know what you meant.

YAGNI is about not doing work in advance. it's very confusing to say YAGNI and pruning in the same breath. it's also confusing to call this aggressive since it's been 10 years.

i wouldn't call it dead code pruning either, since the code in question here was actually reachable and used. maybe, unmaintained code pruning?

Pruning of proposed features maybe?

Rosetta..

Is dead in next year's release (apart from a handful of exceptions).

ZFS

Wait, you can do encrypted backup to a network location but not to HFS+? What if the network location is just your own Mac?

This might be a blessing in disguise for you. The silent data rot of HFS+ is what pushed me to ZFS. I would never go back to HFS+.

>It now seems like there's no real native way of doing encrypted backups to HDDs on macOS

Be happy they let you backup to HDDs at all. :) They don't sell HDDs, so I'm half amazed they still work whatsoever.

Well I'm in your boat. Encrypted sparse bundle disk image on an HFS+ volume seems like it should work, if I'm not missing something. You only need CoreStorage for encrypted HFS+.

Yep, never trust Apple for something they don't rely on to live. For example, don't expect the ecosystem with the Homepod with screen can last for too long. The support will drop and only leave security response if nobody is purchasing.

With macOS 27, I don't know who Apple is trying to outdo?. 27 has been a total disaster for me and my setup at home.

Back when there was a little more rivalry between Microsoft and Apple, Apple would come up with these really cool things to showcase the operating system and make lives easier. Now, I don't know what it is they're trying to prove with this operating system. I also hate the fact that they skinned the whole operating system around a failed hardware product.

I always wait until the new year before I upgrade, I guess this is why I don't seem to have any major problems with it.

I think they're trying to be even shittier than Microslop.

FWIW, this is listed as deprecated in the Release Notes:

https://developer.apple.com/documentation/macos-release-note... (Search for CoreStorage; their fragment links are hilariously broken)

The premier 3rd Party technical blog Eclectic Light talked about it in June: https://eclecticlight.co/2026/06/17/what-to-do-with-your-enc...

I can't immediately find prior warnings that this was coming.

The following technical note from July 22nd says Encrypted HFS+ Volumes won't be supported in macOS *28*, so this seems a bit early... https://support.apple.com/en-us/125615

Also dropped support for FireWire drives, as I just found out the hard way.

> Also dropped support for FireWire drives, as I just found out the hard way.

Erm... it was dropped in macOS 26 back in 2025 ?

https://www.techspot.com/news/108394-usb-killer-dead-apple-d...

And even that was 13 or 14 years after Apple shipped their last computer with a Firewire port - long enough that those computers weren't even supported by macOS 26. Apple dropping support for a largely obsolete technology, which they hadn't used for well over a decade, should hardly come as a great shock.

I had one plugged into the FW800 port of my Cinema Display.

Only really used it as a scratch drive for junk but it was still handy.

Apple's Thunderbolt FireWire 800 adapter daisy-chained with their TB2-to-TB3 adapter should work on any modern system with Thunderbolt and FireWire support, as it just presents as a bog-standard PCI FireWire card.

So worst-case, you should be able to access your old drives on a modern Mac by booting from a FireWire-compatible OS (Asahi or older macOS) on an external drive.

You used to be able to chain three adapters:

Thunderbolt 3 to Thunderbolt 2 Thunderbolt 2 to FireWire 800 FireWire 800 to FireWire 400

to plug a modern Mac into an iMac G4 in Target Disk Mode

Now you need to add another layer: virtualizing old macOS on a modern Mac

But you can still use the original 2005 iMac G5 remote with a new Apple TV

Is it specifically supported, or does it only "work" inasmuch as the Apple TV can be programmed to respond to most IR remotes?

It works out of the box, you don't need to make the Apple TV learn it

It is actually shocking to no longer be able to access my data with literally no warning.

As in, not even a dialog saying "hey this drive isn't support anymore"... just... nothing.

What exactly is Apple gaining by dropping a (presumably) super stable driver??

Nice that you can dismiss this as "largely obsolete technology" tho.

I'd be annoyed. This stuff is usually not a big deal by itself but becomes death by a thousand cuts. Every OS update breaks something.

Ah yes 2025, the ancient times.

Yes, thanks for the correction. I skipped 26 but could no longer hold out :)

did you go from 25 to 27?

Also dropped support for FireWire drives, as I just found out the hard way.

Well, I guess I can finally throw out all those FireWire cables I have "just in case."

Fortunately, my FireWire drives also support other interfaces, though far more slowly.

It's kinda wild how long external HDDs, not even SSDs, were bottlenecking themselves on USB 2. I don't get why they didn't just use eSATA.

Stick them on eBay or at least Freecycle. They are getting hard to find now.

For 2 elderly HP Microservers I need eSATA caddies, and those I cannot find at all anywhere.

Ah. Mine died a few years ago and I just got rid of them, or else I'd have shared.

People are mentioning Firewire hard-drives in this discussion, but much more significant are the industries where other Firewire devices are still in use: such as high-end film-scanning, music production, video archiving, and medical imaging.

Notice that the common thread here is that Firewire was (and is) predominantly a tool for active CREATIVE functionality. Whereas Apple's current focus is passive CONSUMPTION functionality.

MacOs 27 is a disaster. All of the sudden, I have 35% of a computer left to do any kind of work.

Among other signs of awfulness, macOS 27 (and 26 before it) half the battery life of my M1 Air, forcing me to stay on Sequoia for a 2nd year.

What does that mean?

Maybe referring to the Apple Superintelligence being auto-added to macOS 27.

I'll wait for Apple Supremeintelligence in macOS 29

Apple software updates are always a downgrade. It's an opportunity to abuse customers that Apple just can't resist. If you're lucky all they do is break your muscle memory by moving buttons pointlessly.

Gave up on Apple after my MBP is effectively stuck in High Sierra and can't run anything modern, no thanks to the App Store removing older versions of software.

OCLP is a lifeline and works well. After I finally bit the bullet, my iMac is faster than it was before.

It's the iOSsification of macOS. Apparently, newer macBooks will now have touchscreen too ... once iPad OS and macOS are fully merged into OneMacOStoRuleThemAll, they'll finally lock down the bootloader on all Macs (why do you want to install anything else other an Apple OS?) and force all software install only through the App Store.

People have been complaining about this for years and it hasn't happened.

In part it already did.

Large margins, large round corners, now touchscreen.

That’s a long way from locking down the bootloader the go was talking about.

Can you imagine if people said this about political catastrophe?

"Yes, war with Iran has been threatened many times but we can rest assured it will never happen because nobody has done it before."

26 felt like more of a disaster than 27! I waited about 8 months to upgrade to 26, and upgraded to 27 right away.

tar|crypt then

I upgraded and this system is a dumpster fire. Lags, random crashes, performance issues, random CPU spikes...

The author has another recent post from Oct 30 wherein DNS stops working on their machine every week or two. Unsetting/resetting the servers fixes it. I can't imagine daily driving a workstation with flaky DNS.

https://wadetregaskis.com/dns-resolution-failures-in-macos-2...

This happens to me all the time.

For those of you who have never heard of this, it's macos's LVM. Why they didn't just refer to it as LVM is beyond me.

> Why they didn't just refer to it as LVM is beyond me.

Because it isn't LVM, and giving it the same name as another similar-but-distinct technology would just make matters more confusing.

According to the Wikipedia article about CoreStorage, it seems like the primary/only use case was Fusion drives (hybrid SSD/HDD hardware).

The article says “It renders your expensive storage hardware completely useless.” but I’m really curious what that hardware could actually be. This seems like a pretty dead technology.

Sidebar, but as an end user, I remain annoyed that there isn't seemingly something that's a worthy successor to fusion drives.

Like I have an Unraid box with dual NVMe (RAID1) as the "cache" drive and a bunch of spinning disks as the "array", but it's also very manual, like torrents get downloaded first to cache and then a nightly job syncs them to the array. Feels like a real missed opportunity to not be able to have this kind of config transparently managed.

bcachefs with foreground_target/background_target/promote_target set appropriately does this automagically: https://bcachefs.org/Caching/

Ah nice, I appreciate the search term, and I see there are some projects out there leveraging this, for example: https://github.com/nasty-project/nasty

Overall I'm happy enough with Unraid for the moment, but I will definitely check in on bcachefs-based solutions when I'm next considering a rebuild/upgrade.

The successor is SSDs, and I think for what Apple was using fusion drives for they are worthy successors.

The 2.5” form factor also took up a ton of space in a laptop form factor.

With my NAS box (TrueNAS ZFS) I don’t bother with a cache. I struggle to justify the cost/benefit ratio. The sustained write speed of a 3.5” disk isn’t so bad for the most common NAS use cases.

If I could go back to 2024 I think I’d use a m.2 2280 array for my NAS just because my present tense brain would think it was cheap. I don’t even hoard that much content so 4-8TB would be fine.

Maybe one of these nifty things would be fun: https://www.bee-link.com/products/beelink-me-mini-n150

From a pure cost point of view, I think it still makes sense to me to split the load, like 500GB of NVMe covers your containers and apps and stuff, but then 10-20TB of spinning storage is fairly achievable with redundancy, whereas that would cost a fortune to do as all solid state.

The case I have is a Jonsbo N2, which works great for accommodating 5 3.5" drives with backplane, a mini-ITX mobo: https://www.amazon.ca/N2-Aluminum-Support-Integrated-Removab...

Windows storage spaces can do this as well. It's been pulled from the non server line for 11 years or something.

I've gotta agree. I'm not sure what expensive storage hardware would be both relevant today and unable to migrate off CoreStorage. For example, my most expensive storage is a NAS with an iSCSI target, and it couldn't care less what blocks I write to it. If I had a CoreStorage setup on it, I could migrate the data to a new target and then reuse that space for something else. The hardware wouldn't mind, or even know, that I'd changed what's on it.

You mentioned old, obsolete Fusion drives. I'm having a hard time thinking of anything else where that'd matter, so you're probably right about that. AFAIK you can reformat those to use something other than CoreStorage if you're actually stuck using those boat anchors.

I have one of those in an ageing late 2009 27" iMac running Linux. It is a Seagate ST2000DX001-1CM1, a 2TB "SSHD" which comes down to having 8 GB of NAND storage bolted on to a conventional 2TB drive. It doesn't need any special driver to do its thing so I wonder what that CoreStorage bit is supposed to be about.

Apple sold iMacs for many years that had a completely separate SSD and HDD, and CoreStorage was used to combine them into a single block device which was then partitioned and formatted as HFS+ or APFS.

You could also do this to your own SSD and HDD, though probably only a good idea with internal ones like in a Mac Pro

Did you install that SSHD as an aftermarket upgrade? I thought the Fusion Drive configurations shipped by Apple used normal hard drives and separate SSDs and were purely software-managed (and also used much more than 8GB of flash).

CoreStorage was also used for HFS+ formatted and encrypted external storage like Time Machine backups. If you have any of those in your archive you might not be able to read them in the future.

...like route 53? which is "dns configuration, but fancier"

AFAIK "Route 53" was a net new name for such a product?

Does it not manage logical volumes?

Yes it does. It's basically lvm for Mac. I wonder what they do now. Do they go back to old style fixed volumes?

It doesn't really do everything that a real LVM does though. This was used to support those annoyingly bad Fusion Drives. They dropped them around 2020 I think.

> It doesn't really do everything that a real LVM does though.

It manages logical volumes. Any quibbling is a matter of degree.

Why do people try to force macOS things that it does not like to do? macOS does not like not apple hardware, period.

For backups use a NAS. You can find from completely plug and play options to bring your own machine ones.

"Not Apple hardware" meaning an external disk? It's not like the NAS is Apple either. They don't sell NAS or external disks anymore.

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