2012 iMac with too many OS to boot from?

[Racineur]

Hi, my set up may look bizarre but it works for the most part. I have an old iMac 27 late 2012 i5 24Ram, 1 TB Fusion HD with the original Mac OS Mountain Lion still going with full of working apps of the time. I have external SSD connected with El Capitan, Sierra, High Sierra, Mojave and Catalina on each one with I ts own configuration. So I boot in the OS (in a way) I want but actually, Catalina is my main OS. Do you think I should forget about all those OS and install let’s say Catalina on the Fusion Drive, period. What would be the biggest benefits. I was once told a Fusion Drive is slow compared to a SSD be it external. I use my iMac with Safari, Mail and Photos mostly. I also have some photo apps.
Thanks for helping

 

[pmiles]

Why did you set up all those OSes in the first place?

If your system has a fusion drive, you can't run an OS that is based on APFS. That means, High Sierra is the last OS to support MacOS Extended as the system file system. It offers you the option to format in APFS if your hardware supports it. With Mojave and later, MacOS Extended is no longer an option for the system drive.

So you can take your system drive to High Sierra since it is a fusion drive. You can boot into later OSes on an external drive. As to which version of the OS to stick with externally, that is up to you. I don't understand why you have so many versions of the OS unless you have specific software that requires said OS.

You could always replace the internal system drive with a SSD drive which would allow you to run up to Catalina internally. Otherwise you would have to boot to an external drive.

Is there a reason you want to keep this setup? A new M1 iMac is probably a good fit for you sans the smaller display screen. What apps do you use to keep/edit your photos with?

 

[Fishrrman]

OP:
"I was once told a Fusion Drive is slow compared to a SSD be it external."

Download BlackMagic Speed Test (free).
Run it on the fusion drive and then on the SSD.
Post the results here.

The winner (between fusion v. SSD) is where your "main OS" should go.

I liked Mountain Lion (in its time) and stayed with it for a good while.
But eventually it was time to move on.

These days, Mojave is my "main OS" (on a 2018 Mini), but I have an SSD with Monterey as well (may soon get upgraded to the new OS).

What you might consider doing is just "setting the existing SSD aside" (with all the previous OS copies on it). Let it exist "as an archive", safely tucked away.

Get a NEW SSD, put Catalina onto it, and make that your "primary boot drive" (if you find it runs faster than the fusion drive).

 

[Juicy Box]

Regardless of what you end up doing, it might be a good idea to upgrade the OS, at least to High Sierra, on the internal drive to make sure you install the newer firmware. After that, then you can shuffle the various OS around to the drives you choose.

Also, regardless of the OS you choose to use, I would go with an external SSD versus using the internal Fusion Drive. The HDD of your Fusion Drive is getting really old. The SSD is probably also heading towards end of life as well.

The winner (between fusion v. SSD) is where your "main OS" should go.

I wouldn't say that this is a universal way of picking the best drive to use.

Newer iMac 1TB Fusion Drives with only 24GB or 32GB of an SSD portion can get impressive BMDST numbers, faster than an external USB3 Gen2 SSD. But, I would still recommend going with the pure SSD.

Also, BMDST only does sequential reads and writes, which for boot drives, I think random would be a better metric.

A good example is comparing an internal SATAIII HDD versus an external FW800 SSD. A newer HDD would destroy the FW800 SSD when it comes to sequential reads and writes, but at random, the FW800 SSD would be a lot faster. For use as a boot drive, the FW800 SSD would feel a lot more responsive, open apps faster, and boot faster than the HDD.

Not this applies to the OP and his Late 2012 iMac, but for anyone else that reads the thread looking for advice on their different Mac, it might be helpful to point out that straight BMDST numbers don't tell the whole story, especially for boot drives.

I like AmorphousDiskMark, as it tests both sequential and random.

 

[Mr_Brightside_@]

Why did you set up all those OSes in the first place?

If your system has a fusion drive, you can't run an OS that is based on APFS. That means, High Sierra is the last OS to support MacOS Extended as the system file system. It offers you the option to format in APFS if your hardware supports it. With Mojave and later, MacOS Extended is no longer an option for the system drive.

So you can take your system drive to High Sierra since it is a fusion drive. You can boot into later OSes on an external drive. As to which version of the OS to stick with externally, that is up to you. I don't understand why you have so many versions of the OS unless you have specific software that requires said OS.

You could always replace the internal system drive with a SSD drive which would allow you to run up to Catalina internally. Otherwise you would have to boot to an external drive.

Is there a reason you want to keep this setup? A new M1 iMac is probably a good fit for you sans the smaller display screen. What apps do you use to keep/edit your photos with?

How come I was able to install Sur on a FD iMac then?