Running 2015 iMac from external SSD? How to set up?

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Running 2015 iMac from external SSD? How to set up?

We have a 2015 21 inch iMac with a spinning disc hard drive that is so slow it's unbearable. I have an SSD that I'm not using and I'd like to run the computer from that drive via USB. I've seen this mentioned with the use of an adaptor cable, of which I have two.

The iMac has Ventura installed and what I'd like is to install Ventura on the external SSD and boot from that.

However, all the instructions I've found online seem confusing or don't open the dialogs they mention, etc.

Can someone provide accurate step by step instructions on how to set up the drive?

Specs: iMac--2015 or so 21", running Ventura. 8GB memory, 1TB HDD 5400 rpm. External SSD--500GB 3GB/sec, SATA II (it mounts with USB adaptor but there's nothing on it)

Thanks in advance!

Earlier Mac models

Posted on Dec 11, 2023 4:00 PM

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Answer 1

Dec 14, 2023 2:55 PM in response to SchenkerBob

<<. there are several different ways to install the OS (Ventura) and I can't figure out the best way to go. >>

If you have ANY version of macOS running, it is ALWAYS superior to use running MacOS to download the version you want. The Mac App Store will get it for you, BUT -- you must use the link in this article, as directed. a large binary will be placed, ready to run the installer, in the /Applications folder.

Then you find that "Install MacOS Ventura.."time and double-click on it, and it will first copy a lot of files and a MacOS Base System to the destination drive, then boot from that to complete the Install.

How to download and install macOS - Apple Support

when it tells you where it is going to install, you click (show all disks) and [provided your drive is erased and ready] the new drive will be shown as a destination. Select it and proceed.

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Answer 2

den.thed

Level 10

90,946 points

Dec 11, 2023 4:27 PM in response to SchenkerBob

Jack-19 has put together an awesome User Tip for just that.

see > Use an external SSD as your startup disk … - Apple Community

1) I recommend using a USB 3.0 2.5" SATA External Enclosure instead of using a USB drive adapter.

for example > https://www.amazon.com/Sabrent-Tool-free-Enclosure-Optimized-EC-UASP/dp/B00OJ3UJ2S?

2) Not sure what SATA ll SSD you have, but you'd get better performance from a SATA 6G SSD.

for example > https://www.amazon.com/Crucial-MX500-500GB-NAND-Internal/dp/B078211KBB?th=1

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Answer 3

SchenkerBob Author

Level 1

97 points

Dec 14, 2023 2:40 PM in response to den.thed

I'm still a bit unclear as to how to get this install to go onto the external SSD. And I think the iMac is actually a 2017, rather than my description of it as a 2015. Per the above suggestions, I have a 6G SSD in my main Mac and it is really great, but I have used the 3G ones in my computers and for this project It will be plenty fast, certainly vastly faster than the 5400 HD in the computer now, which runs really really sluggishly. I did call OWC, who supplied the 3G Mercury 500GB SSD I'm planning to use, and they said it should present no problems used to run the computer externally, with or without an enclosure, etc.

I've tried installing the OS on the SSD but I am missing something somewhere. I looked at a bunch of Apple Support pages but that only made me more confused, since there are several different ways to install the OS (Ventura) and I can't figure out the best way to go.

I would like to have the OS start up and run the computer from the external SSD. It's currently running and booting from the internal and it is really really slow.

Any further tips would be welcome.

Bob

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Answer 4

SchenkerBob Author

Level 1

97 points

Dec 14, 2023 3:08 PM in response to SchenkerBob

I got your message, but when I go to the link, there are five different links plus the help link. I've been here before and I don't understand which one to open.

Use Software Recovery

Use Mac OS Recovery

Use the App Store

Use a web browser

Use a bootable installer

If you need help

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Answer 5

Dec 14, 2023 3:13 PM in response to SchenkerBob

Because you have a working MacOS already installed, you want to use the full power of MacOS to do the job.

"Use the App Store"

... and it will show you a list. Click the version you want, and it may go to it in the App store, and you can "Get" it by pressing that button. Takes half an hour or more at typical broadband speeds to complete just the download, but your computer is usable while it is progressing.

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Answer 6

SchenkerBob Author

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97 points

Dec 14, 2023 3:14 PM in response to SchenkerBob

So I just tried that. What I get is the Ventura Utilities link. That has been what's confusing to me. I was reluctant to try it and dig myself a hole. But per your description I just did try it and it is downloading the OS. I will get back to you with what happens, once it finally does.

Thanks ever so much for your patience.

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Answer 7

Dec 14, 2023 4:33 PM in response to SchenkerBob

The reason you don't see the MacOS installer directly when you look for it in the App Store yourself is that they are "put away' so that users do not download them 'by mistake'.

You need to use the links in the article, and then they appear.

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Answer 8

SchenkerBob Author

Level 1

97 points

Dec 14, 2023 3:11 PM in response to SchenkerBob

OK, looking at this yet again, I think I understand that I need to use the "Use the App Store" link and then choose Ventura there. Am I getting warmer?

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Answer 9

SchenkerBob Author

Level 1

97 points

Dec 14, 2023 3:44 PM in response to SchenkerBob

YAAAAY!!! Got it! Thanks so much!

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Running 2015 iMac from external SSD? How to set up?

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