Can I have 2 Catalina systems on separate partitions in the same internal drive?


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I recently "upgraded" a Trash Can Mac Pro from Mojave to Catalina. After about a week (and after the Safari update, though I don't know it's related), the WidowServer crashes and then there's a kernel panic. I have thousands of apps and plugins going back to Yosemite, so I figure it's easier to do a fresh start than troubleshoot the crashes. It's long overdue anyway.

It's gonna take me a LONG time to install? Update, and authorize everything. I'd like to install a fresh copy of Catalina on a separate partition on the same drive so I can boot into a semi-functional system when I need to.

It used to be a very simple thing to do this, but I'm not as familiar with the new macOSes. I looked into doing the same thing with Big Sur, but that looked way more complex than beneficial. I can't think of any reason why two Catalina partitions would cause issues, but would really appreciate a more experienced perspective and any suggestions to make this go smoothly.

Thanks!
 
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It is not something that I have done, but I see no reason for it not to work. Just give the new partition a different nam,e so that you can differentiate them.
Another alternative is to do a clean install on an external drive.
 
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It is not something that I have done, but I see no reason for it not to work. Just give the new partition a different nam,e so that you can differentiate them.
Another alternative is to do a clean install on an external drive.
Thanks. That was my thinking. Unfortunately, I don't have an external SSD — only magnetic drives — and one's not in the budget. I don't think Catalina will like that! I'll post the results here once I try it since I wasn't able to find an answer anywhere. Hopefully it'll help someone.
 
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An external will definitely work. I have High Sierra, El Capitan, Mojave and Catalina on externals some SSD and some mechanical drives. They come in handy for troubleshooting.
 
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Using the Disk Partition software, you can easily create two GUID partitions; they will appear as separate devices.

*** BUT ***

Doing this will destroy all the data on your internal hard drive. Since you can get a 1TB external drive for around $60, you really should invest in one so that you have some kind of backup capability.

Also be aware that Catalina (and later) uses Apples "new and improved" Apple File System (APFS), which favors SSD drives over spinning platter drives. I run a Mac Mini mid-2014 which has a slower 5200rpm drive, and I actually got better performance by buying an external 4Tb G-Tech spinning platter drive (7200rpm with 64Mb cache: $140) and connecting it to the Mini using a USB3 port. So that's how I run, and I use Carbon Copy Cloner to keep the internal hard drive in sync with the external. Both are bootable; if the external hard drive fails, I can at least boot off the internal hard drive and tolerate lackluster performance until I replace the external drive.

I also have an older G-Tech drive with 2TB of space on it, and I have it divided up into 3 partitions: the original El Capitan that used to reside on the internal hard drive, a partition called "NewOS" where I can do test installs, and a partition for Time Machine. Both the El Cap and NewOS partitions are bootable. Once I decided to go with Catalina, I used CarbonCopy to clone the external hard drive to the internal drive (repartitioning and overwriting the original El Capitan install), because I can always boot off of the El Cap partition on the external hard drive if I ever need to go back for something.

Why keep the old one around? I had VMware Fusion installed and a Windows 7 virtual machine running under that. To install
Fusion on Catalina costs $199, which is more than twice what I originally paid for Fusion when I first installed it. Given the amount of use that I make of the Windows 7 virtual machine, I can't justify the cost when the alternative is to simply boot up El Cap when I need it, and then reboot into Catalina when I'm done.

I could have upgraded the internal hard drive, but the Mini's internals are very, very tightly fitted and you have to remove most of the "innards" to get at the hard disk. I concluded that with the kind of luck I have, this was a job better left to professionals with the right tools and the right experience, but the quote came in at $345 parts and labor for a 500Gb SSD drive, and as I noted earlier, I could buy a 4Tb G-Tech drive for less than that and get more space besides.

I'm a belt-and-suspenders man, and I have done my share of upgrades and migrations. I always do a clean install, and because of that, I always ensure I have a bootable backup version of my running system first before beginning a new installation.

A Mac Pro is a nice machine: good luck with your endeavors!
 
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