Replace Fusion Drive in 27" iMac

peterpatter wrote:

Thanks so much for your information. As I've never, so far, had need for the USB3 ports, I had forgotten that they were there. How stupid can I be? To transfer files between my iMac and my MB Air (M1 chip), is a cable between the respective USB3 ports the best way of doing this?

If you are talking about Target Disk Mode or the equivalent, I do not believe that a USB cable would let you use the iMac as a Target Disk for the M1 MacBook Air.

Transfer files between two Mac computers using target disk mode - Apple Support

"Note: If either of the computers has macOS 11 or later installed, you must connect the two computers using a Thunderbolt cable."

You would need to use a Thunderbolt cable to connect the two Macs. The Thunderbolt cable would have USB-C plugs on either end, but would rated to carry Thunderbolt traffic (and would be more expensive because of that).

If you wanted to use the M1 MacBook Air as an "external drive" for the 2017 iMac, then you could use a USB cable that went from USB-A or USB-C (on the 2017 iMac end) to USB-C (on the M1 MacBook Air).

Transfer files between a Mac with Apple silicon and another Mac - Apple Support

I'm guessing it's easier to bypass this, and do the transfer with the aid of

• An external drive (plugged into one Mac at a time), or
• iCloud Drive (for small numbers of files) – put files into iCloud Drive and they will be available to either Mac

If you were setting up a new Mac for the first time, and wanted to transfer things from the old Mac, a common way to do that is to take a current backup (Time Machine, Carbon Copy Cloner, Super Duper!) from the old machine, attach it to the new one, and tell Migration Assistant to migrate from that backup. But it sounds like you already have both machines set up and so would not want to do a blanket migration.

peterpatter wrote:

Thanks so much for that useful information. Does it matter if the 27" iMac is on macOS Ventura 13.7.4 with an Intel Core i5 processor, while the 13" MBA is running with Ventura and an Apple M1 chip? If I upgraded the MBA to macOS Sequoia, would they still be compatible with each other for transferring files between them, using either a thunderbolt cable or iCloud?

If one Mac has an Intel chip, and the other has an Apple Silicon one, I would not expect a startup disk for one to work on the other – even if both startup disks contained the same version of Ventura. Presumably the installers are set up so that most of the installation of for the Intel Mac is Intel-only code, while most of the installation for the Apple Silicon Mac is ARM-only code.

That wouldn't keep you from migrating from the old Mac to the new one – whether you use a cable, or a current backup. Migration Assistant copies data and applications. It doesn't blindly copy over all the parts of the old OS.

The limitations on Target Disk Mode are still the same as before. Since you have at least one computer which is running Big Sur or later, you must use Thunderbolt if you want to use the Intel-based Mac as an external "disk"; but you can use either USB or Thunderbolt if you want to use the Apple-Silicon-based Mac as one.

Transfer files between two Mac computers using target disk mode - Apple Support

Transfer files between a Mac with Apple silicon and another Mac - Apple Support

Alternatives to that include using iCloud Drive. using network File Sharing, or simply copying files to an external drive and then transferring that drive from one Mac to the other.

Do you know how far I can upgrade my iMac OS, or is Ventura the limit for it? I've read somewhere that I probably can't go up beyond Ventura.

You said that your iMac was a 2017 model? If so, Ventura is as far as it can go.

macOS Ventura is compatible with these computers - Apple Support

macOS Sonoma is compatible with these computers - Apple Support

macOS Sequoia is compatible with these computers - Apple Support

peterpatter wrote:

Hi Servant of Cats,

Thanks for your valuable information. It seems my 2017 iMac can only go as far as Ventura, but my M1 MB Air can go to Sequoia. Should I upgrade it? Will there be any problems with transferring files, etc. between them?

There shouldn't be much of a problem with transferring individual files. However, whenever you upgrade macOS, there's a possibility that Apple will have decided to change the format of the Music / TV (iTunes) database or the Photos (iPhoto) database.

If that is the case, you can usually take the libraries forward a version or two (e.g., from Ventura to Sequoia), and the applications will automatically upgrade the library format as needed. But once the libraries are converted, it may be more difficult to take the library back.

I don't know that this has happened with Ventura vs. Sequoia, specifically; just that it happens sometimes.

I now have my 2TB OWC Envoy SSD, so will be setting it up on my 2017 iMac with Ventura, as the startup drive and transferring all my data to it. I trust that all will go go smoothly thanks to your valuable guidance. While I am at it, should I consider increasing my Memory from 8 GB to 16 GB?

You can upgrade RAM on your 27" iMac – and if running Activity Monitor while you are doing stuff that uses a lot of RAM shows that 8 GB is not enough, you could consider doing so. (If you were doing heavy Photoshop work – or running virtual machines – on that 27" iMac, you might consider putting in 32 GB.)

I would suggest buying RAM for the 27" iMac only from Other World Computing. Macs can be picky about RAM, and the other "go to" Mac RAM vendor (Crucial) seems to have gotten out of that particular business.

You cannot upgrade RAM on any Apple Silicon Mac. If your M1 MacBook Air has only 8 GB of RAM, there is no way to upgrade that short of replacing that Mac with another one that has more.

P.S.:

A couple of notes based on my experience upgrading from Ventura to Sonoma on a M1 Max Mac Studio.

I'm not sure if I mentioned this in this thread, but Sequoia has a couple of annoying default Settings that you may want to change. Both are in System Settings > Desktop & Dock.

• Under the Desktop & Stage Manager section, you may want to change Click wallpaper to reveal desktop from Always to Only in Stage Manager. This keeps your windows from flying away when you're just trying to click on an empty space on the Desktop in preparation for making another selection.
• Under the Windows section, you will almost certainly want to turn off Drag windows to menu bar to fill screen. If you work with windows that take up most of the space on the screen, this one tends to destroy your carefully planned windows arrangement when you are making small window positioning or resizing changes.

I thought I was going to need to do something special to give Music and TV permission to access optical discs. So I looked for the controls in Settings, but they weren't there. Then I ran the Music and TV applications, and the first time that I ran each (after the upgrade), it asked for permission (which I granted) and made the necessary settings change. So that wasn't a problem.

peterpatter wrote:

Hi Servant of Cats,

My 4TB Time Machine drive still has all the backups from my Macintosh HD on it, and is now continuing in the same manner by backing up to the new OWC Envoy SSD. To prevent the Time Machine drive from getting too full, is it easy to just delete old backups from the past? That is, into the Bin, using Finder?

I do not use Time Machine – I make other types of backups. However, I believe that Time Machine does not want you going behind its back using the Finder or Terminal. That might be akin to taking a screwdriver and using it to poke around in the inside of your car's automatic transmission – when what you should be doing if you would like to avoid an expensive repair job is to use the control for selecting Park, Reverse, Neutral, or Drive.

Back up your Mac with Time Machine - Apple Support

If the Time Machine backup disk for your Mac is full - Apple Support

The second article indicates that if your Time Machine backup disk starts getting full, Time Machine itself will get rid of older backups to make space for new ones.

I have not deleted anything from the Macintosh HD, which is now hibernating and out of action. I think you mentioned that I could use it as an "external" drive from now on. Is this correct?

Yes. As long as it's working, you could eject it and let the hard drive spin down, or you could reuse it for anything. Keeping a bootable system on it might be worthwhile to have something to recover from should your external SSD get corrupted or fail. If it's big enough, you could make periodic clone backups of your SSD onto it to supplement the Time Machine backup. But it's really just whatever you think would be most convenient.

The advise from @ Servant of Cats should be followed