Need help partitioning hard drive

[DianeK]

I have an iMac 27" 2013 with 3TB hard drive. I am running Sierra because if I update beyond that I lose access to expensive, non-subscription Adobe software. I have just lost the capability to sync my newer iPad and iPhone via iTunes. This is the message that appears when I connect my devices:

I was advised to partition my hard drive and install Catalina, which is the final OS that can be put on this older omputer, in order to use Finder to sync my iPad and iPhone. However, when I researched on the Apple site, it says I need High Sierra in order to partition.

Does anyone here have advice on how I can accomplish the partitioning of my drive with Sierra, not High Sierra?

Thank you

 

[Nermal]

The update that iTunes is talking about is not a full OS upgrade. You should be able to remain on the same OS even if you install the iOS support update.

 

[DianeK]

The update that iTunes is talking about is not a full OS upgrade. You should be able to remain on the same OS even if you install the iOS support update.

Thank you Nermal. I am reluctant to hit install because I don’t really know what this is installing. If I knew it was just iTunes fine. But if it is an actual OS update I’m screwed. Clicking “Learn more” gives me no information about what the update is.

 

[DianeK]

And since Apple has stopped supporting iTunes I am doubly suspicious That this isn’t just an iTunes update. If you have more information than I have been able to gather I‘m all ears.

 

[DianeK]

Sorry, keep hitting post before I’m done. The pop up message appears on my iMac, not the mobile devices, which is why I fear the update is an OS update, not an iTunes update.

 

[Nermal]

It's neither an OS update nor an iTunes update. It's iOS support software, i.e. the thing that lets Mac apps (such as iTunes) "talk" with newer iOS versions. It will not change your OS or iTunes versions.

 

[DianeK]

Promise?!?

 

[Fishrrman]

OP:

I would advise you to NOT partition the drive, particularly if it's a fusion drive (which I think the 3tb drive is).

Instead, if you need to boot a newer version of the OS (while keeping the old version), get an EXTERNAL SSD, and install the newer OS onto the external SSD.

It's not hard to do this, anyone can do it. If I could do it, you can, too.

What you'll need:
a. A 2.5" SATA SSD. You can get a 256gb SSD **for cheap** (but don't buy "too cheap"):

Amazon.com: 2.5" 256gb SATA Ssd

Amazon.com: 2.5" 256gb SATA ssd

www.amazon.com

Sandisk or Crucial would probably do fine.

b. Then, get a 2.5" USB3 enclosure like this:

SABRENT 2.5 Inch SATA to USB 3.0 Tool Free Clear External Hard Drive Enclosure [Optimized for SSD, Supports UASP SATA III] (EC-OCUB)

SABRENT 2.5 Inch SATA to USB 3.0 Tool Free Clear External Hard Drive Enclosure [Optimized for SSD, Supports UASP SATA III] (EC-OCUB)

www.amazon.com

Put the drive into the enclosure -- it just snaps together.

Now that the drive is ready and waiting, we need to install the OS onto it.
So... boot to INTERNET recovery (NOT to the recovery partition) by doing this:
Command-OPTION-R
at boot

The internet utilities take a while to load, be patient as the globe spins.
When you get to the utilities, connect the external SSD.
It may throw up an error, because we haven't initialized it yet.
So... open disk utility.
VERY IMPORTANT STEP, DO NOT SKIP: go to the "view" menu and choose "show all devices".

Now, look at "the list on the left".
You can see the new drive, as-yet un-initialized.
Click on it to select it, then choose erase.
You want "APFS, GUID partition format".
When the drive is erased, quit disk utility.

Now, open the OS installer and start clicking through.
VERY VERY IMPORTANT:
When the installer asks WHERE you want to install, DO NOT blindly click the internal drive!
MAKE SURE you select the external SSD to proceed.

As the install proceeds, the Mac will reboot one or more times, and the screen will go dark for a minute or more with no other indication of activity. Be patient.

When done, you should see the initial setup screen "choose your language".
Start clicking through to setup the new OS.
You'll have to set up the desktop, install applications, etc.

All this sounds like "a little work", and it is.
But if you PRINT OUT this reply and follow it for reference, I predict you will have a high probability of success.

Good luck!

 

[DianeK]

Thank you Fishrrman.
My internal drive is not a fusion drive, just a regular spinning drive. I have a G-Tech external connected to the computer for my Time Machine backups. I had the external partitioned at time of purchase with the idea I would put a bootable clone on the non-Time Machine partition but never got around to doing that, so it is blank. It is formatted Mac OS Extended (Journaled). Would I need to format it to APFS, GUID or be able to use it as it is currently formatted?

 

[DianeK]

Just spent a long time with Apple Support.

To Nermal: they confirmed that the pop up to update is in fact a forced update of my OS and will overwrite my Sierra to a higher OS version - so NOT going there.

To Fishrrman: they confirmed that to use Catalina as my optional boot drive does require APFS GUID - I can't use Mac OS Extended. BUT because I use this external as my Time Machine backups they strongly recommended against using the extra partition for a bootable drive because when Time Machine kicks in things can go badly when I'm operating in the separate partition.

Solutions offered were:
1. Get a separate hard drive to put Catalina on and move everything non-Adobe related to it and it becomes my main operating hard drive, or
2. Get a new computer (could see that coming) and move my lovely iMac to the corner and only boot it up when I need to use my Adobe suite.

 

[Fishrrman]

OP:

I think you could use disk utility to re-initialize (erase) the unused partition to APFS, and then install Catalina onto that.

BUT consider...
Being a platter-based drive, it will run, but probably not very fast.
In fact, it might be quite SLOW. I predict you won't like it.

You'll do MUCH better by using a USB3 SSD for the external boot drive, as I mentioned above.

 

[DianeK]

OP:
You'll do MUCH better by using a USB3 SSD for the external boot drive, as I mentioned above.

I agree. Hubby is urging me to just get a new MacBook Pro and shove the iMac into the corner for occasional use. But my current mood is to not give Apple any more of my money when they do stuff like this to force people to buy more of their computers.