Boot OS X from external SSD

varian55zx

macrumors 6502a
Original poster
May 10, 2012
748
260
San Francisco
I have an older iMac that I would like to now put OS X on an external SSD and boot from it, along with all the apps on the computer, but (edit: ) accessing everything else on the internal HD of the Mac by changing the system's home folder to that of the one on the internal, thus, in my mind, getting the 'best of both worlds'.

Strangely, I must be the first person online to ask this question.

Is this feasible to do? Would I experience all the benefits of the SSD with only having the apps and OS on it while keeping all other files on the internal?

Should I buy a thunderbolt or USB 3 enclosure? Apparently this is another subject that just nobody knows about, because I see many people saying you can't external boot from USB 3, however, as I understand it, you can. But which is better for this?

Scary so many people think you can't.

Is this a feasible plan? Is there a particular SSD that is best suited for this?

Also, what exactly is TRIM and why would I care?

Thanks a lot for any help.
 
Last edited:

keysofanxiety

macrumors G3
Nov 23, 2011
9,534
25,264
I have an older iMac that I would like to now put OS X on an external SSD and boot from it, along with all the apps on the computer, while keeping everything else on the internal HD of the Mac.

Strangely, I must be the first person online to ask this question.

Is this feasible to do? Would I experience all the benefits of the SSD with only having the apps and OS on it while keeping all other files on the internal?

Should i buy a thunderbolt or USB 3 enclosure? Apparently this is another subject that just nobody knows about, because I see many people saying you can't external boot from USB 3, however, as I understand it, you can. But which is better for this?

Scary so many people think you can't.

Is this a feasible plan? Is there a particular SSD that is best suited for this?

Also, what exactly is TRIM and why would I care?

Thanks a lot for any help.
USB SATA 3 dock, save some cash. I'd recommend any Crucial or Samsung SSD, but that's just personal preference as in my experience they don't have any problems.

Hold CMD+R to boot into Recovery partition with the SSD plugged in via USB. Go into Disk Utility in OS X Utilities. Format SSD through Disk Utility. Click Reinstall OS X. Set to install directly onto the SSD. Sorted.

Then hold Alt on startup and select the SSD. Hold Ctrl and press Enter so it boots into SSD by default.

Open Migration Assistant in OS X, transfer all apps/data that way.

EDIT: if you have an older iMac it's not likely to have USB 3. As such the performance benefits of an external SSD will be negligible. Therefore I'd recommend fitting the SSD inside rather than running externally. You can still install the OS by booting into the recovery partition externally on the old HDD, or you can run through the above instructions then swap out the HDD with the SSD.

Also depending on the model it may be a 3.5" HDD rather than 2.5" as the SSDs are, so you might need to get an enclosure for it to fit.
 
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varian55zx

macrumors 6502a
Original poster
May 10, 2012
748
260
San Francisco
Thanks, that was a very informative response.

My only other question is, my intention was to set the home folder of the SSD to the one on the internal, through Users & Groups in System Preferences, thus having access to everything on the internal as if I was booting from it itself.

However, I wanted to try and get the apps to boot off the SSD, to get the benefit of the SSD speed, thus my reference to having only the apps and OS on there. Is that a realistic thing to do?

Also, not to worry. It is an older Mac but it has USB 3 and thunderbolt capability. I would be willing to spend more for the thunderbolt, should the difference be very apparent. If the difference is negligible, then I wouldn't see the necessity to pay.
 

Fishrrman

macrumors Core
Feb 20, 2009
19,950
6,985
It's trivially easy to boot and run a Mac from an "external booter".
I've been doing it for years.
Almost nothing to it (I said, "almost").

Fastest, easiest, cheapest way is to get something like this:
http://www.amazon.com/exec/obidos/ASIN/B00ZTRY532?tag=delt-20

Just plug it in, use a cloning app like CarbonCopyCloner or SuperDuper to "clone over" your OS, apps, and accounts.
You'll be back to booting and running in about 10 minutes.

Or, buy a "bare" 2.5" SSD of your choice, and a USB3 enclosure such as this:
http://www.amazon.com/MiniPro-Exter...8-1&keywords=oyen+digital+2.5"+usb3+enclosure

Put the drive into the enclosure, connect it, initialize it, clone to it, ready to go.

Be aware that you can't use TRIM when connecting via USB.
Some will claim that it will slow down the drive as time goes by, but I've been booting and running my Mac Mini via an SSD in a USB3 enclosure for three years now, without any perceptible speed differences at all.
It just works.
 

varian55zx

macrumors 6502a
Original poster
May 10, 2012
748
260
San Francisco
It's trivially easy to boot and run a Mac from an "external booter".
I've been doing it for years.
Almost nothing to it (I said, "almost").

Fastest, easiest, cheapest way is to get something like this:
http://www.amazon.com/exec/obidos/ASIN/B00ZTRY532?tag=delt-20

Just plug it in, use a cloning app like CarbonCopyCloner or SuperDuper to "clone over" your OS, apps, and accounts.
You'll be back to booting and running in about 10 minutes.

Or, buy a "bare" 2.5" SSD of your choice, and a USB3 enclosure such as this:
http://www.amazon.com/MiniPro-External-Aluminum-Drive-Enclosure/dp/B003VKTJGW/ref=sr_1_1?ie=UTF8&qid=1455205484&sr=8-1&keywords=oyen+digital+2.5"+usb3+enclosure

Put the drive into the enclosure, connect it, initialize it, clone to it, ready to go.

Be aware that you can't use TRIM when connecting via USB.
Some will claim that it will slow down the drive as time goes by, but I've been booting and running my Mac Mini via an SSD in a USB3 enclosure for three years now, without any perceptible speed differences at all.
It just works.
Thanks a lot, that was very helpful.

My only question though is how can I boot from the external ssd, while keeping all other data on the internal? Is that achieved by changing the home folder in Users & Groups?
 

hfg

macrumors 68040
Dec 1, 2006
3,589
283
Cedar Rapids, IA. USA
Thanks a lot, that was very helpful.

My only question though is how can I boot from the external ssd, while keeping all other data on the internal? Is that achieved by changing the home folder in Users & Groups?
I believe that is the Apple recommended way to do what you want to do. I seem to recall that there was a support page on the Apple web site which discussed moving your home folder to another disk and detailed that method.
 
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varian55zx

macrumors 6502a
Original poster
May 10, 2012
748
260
San Francisco
I believe that is the Apple recommended way to do what you want to do. I seem to recall that there was a support page on the Apple web site which discussed moving your home folder to another disk and detailed that method.
I've seen a lot of threads on that too. I really have no interest in doing that though. I have >600gb of stuff on my internal, I won't be moving that to a tiny SSD.

I want to have merely OS X and all of my apps on the SSD, in my mind I will have the full benefits of SSD that way. Is there anything else I would need to move over?

Also, how would I go about running the apps from the SSD while using the home folder of my internal? Is that possible?

Thank you so much for any help.
 

warvanov

macrumors 6502a
Oct 13, 2011
504
7
I want to have merely OS X and all of my apps on the SSD, in my mind I will have the full benefits of SSD that way.
That's exactly what I did on my MacBook Pro the other day and it was a piece of cake to do. I added an SSD as a second internal drive. I installed OSX on the new drive and it gave me the option to import the system configuration, applications, and data. I imported the system config and apps, but not the data. Once I booted up I changed the users and groups preferences to my existing folder on the old drive. Now all my files are on the old 1TB HDD, and all my system and applications are on the new SSD, and everything is configured as I had it before down to the desktop background and dock. Easy peasy.
 
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varian55zx

macrumors 6502a
Original poster
May 10, 2012
748
260
San Francisco
That's exactly what I did on my MacBook Pro the other day and it was a piece of cake to do. I added an SSD as a second internal drive. I installed OSX on the new drive and it gave me the option to import the system configuration, applications, and data. I imported the system config and apps, but not the data. Once I booted up I changed the users and groups preferences to my existing folder on the old drive. Now all my files are on the old 1TB HDD, and all my system and applications are on the new SSD, and everything is configured as I had it before down to the desktop background and dock. Easy peasy.
Man, thank you so much.

This was EXACTLY what I was wondering, not only how to do it, but also if it was easy. Thank you so much, man! I'm totally sold on this idea. I'll be doing the exact same thing you did, but with an external drive.
 
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Ben777

macrumors member
Jun 24, 2013
70
4
Man, thank you so much.

This was EXACTLY what I was wondering, not only how to do it, but also if it was easy. Thank you so much, man! I'm totally sold on this idea. I'll be doing the exact same thing you did, but with an external drive.
Well, did it work? :) I am about to try to do the same...
 

nambuccaheadsau

macrumors 68000
Oct 19, 2007
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Nambucca Heads Australia
What you can do Ben is connect the external using a caddy, or case, and connect via USB3 and you most assuredly want to be using an SSD in the caddy to make the most bof speed advantages. Boot up and go into Disk Utility and check the drive is visible and format Mac OS Extended.

Using SuperDuper or CarbonCopyClone, clone the internal drive to the external and make sure the 'Make Bootable'. Go into System Preferences > Startup Disk and make sure the external is in the list of available disks. Select by highlighting and hit "Restart' and it should then boot from the external.

Also, on bootup you can immewdiately hold down the Option key and select the external from the list available
 

Ben777

macrumors member
Jun 24, 2013
70
4
What you can do Ben is connect the external using a caddy, or case, and connect via USB3 and you most assuredly want to be using an SSD in the caddy to make the most bof speed advantages. Boot up and go into Disk Utility and check the drive is visible and format Mac OS Extended.

Using SuperDuper or CarbonCopyClone, clone the internal drive to the external and make sure the 'Make Bootable'. Go into System Preferences > Startup Disk and make sure the external is in the list of available disks. Select by highlighting and hit "Restart' and it should then boot from the external.

Also, on bootup you can immewdiately hold down the Option key and select the external from the list available
Thanks a lot! So does this mean that I will be having OS installed on two locations - both iMac and external SSD? And I use SSD as my bootable disc, so that OS runs from SSD? Is this the case?

How about applications? They will be also moved to external SSD (or I move them manually, if I do installation from the scrach, right?). Should I just erase applications form my iMac? Or I leave them to be?

Thanks a lot!
 

TomM1

macrumors member
Sep 28, 2017
31
3
So after cloning the HD to an external SSD (to run the OS from the EX SSD) can the internal platter HD be used for a Time Machine backup?
If so does it need to be erased first?
Late 2015 iMac, Mohave.
 

TomM1

macrumors member
Sep 28, 2017
31
3
Ok here is another question. I have read many threads about APSF vs HFS. My understanding is not deep.
Having cloned my HD to an external SSD( Samsung SSD T5 USB3) the system profile lists the two like this:
Macintosh HD, File System: APFS
EX SSD, File System: Journaled HFS+
Is this correct and best configuration?
Thanks.
 
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nambuccaheadsau

macrumors 68000
Oct 19, 2007
1,842
434
Nambucca Heads Australia
It is nup to ytou.

I run two external SSDs. one via USB3 and one via TB and formatted both of them to APFS and no problems at all. To do this you nneed to select the external in DU, erase and format APFAS and then clone internal to external.

Why run two external SSDs? As the Irish say 'To be sure; to be sure".
 

Ben777

macrumors member
Jun 24, 2013
70
4
I figured out I cannot clone internal HDD to external SSD, as there is not enough space on SSD for all the data from HDD.

So, probably, I should do everything from scratch? Which means installing OS on external SSD from scratch? Should I move all applications also to external SSD for them to work faster?

Then, when I boot iMac from SSD drive, will it automatically use applications from SSD?

Thanks!
 

Fishrrman

macrumors Core
Feb 20, 2009
19,950
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Ben777 wrote:
"I figured out I cannot clone internal HDD to external SSD, as there is not enough space on SSD for all the data from HDD."

If you're using CarbonCopyCloner, you can still do a "partial clone" -- enough to get the OS, apps, and basic accounts over.

What you need to do is open CCC, set up the internal to be the source and the external to become the target.

Then, to the middle-left there is a popup menu, "Clone".
It offers the choice of "all files", or "some files".
Choose "some files".

Now you have to start UNCHECKING those folders/files you want to "leave behind".

Some CAREFUL THOUGHT is involved here.

I would open my users folder, pick my account, and "leave behind"
- pictures
- movies
- music

At least for now.
That's often where "the bulk of stuff" is stored.

Again, what you bring over and what you leave behind will be UP TO YOU after a careful examination of what's on your drive.

But doing it this way will result in the IMPORTANT STUFF being cloned over.
 
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Ben777

macrumors member
Jun 24, 2013
70
4
Dear Fishrrman, So I did clone the disc. The procedure was easy!

What's next? Start iMac with holding option key, then choose SSD? That's it? :)
 

Fishrrman

macrumors Core
Feb 20, 2009
19,950
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IF the clone is done, do this next:
a. disconnect the cloned backup
b. press power on button
c. IMMEDIATELY hold down the option key, and KEEP HOLDING IT DOWN until the startup manager appears.
d. You should see the SSD "available for choosing"
e. Select it with the pointer and hit return
f. Do you get "a good boot"? You should
g. NOT FINISHED YET -- open System Preferences then the startup disk pref pane
h. Click the lock. Enter your password. Click the icon for the SSD. Close system preferences.

NOW, final check:
1. Power down, all the way off
2. Press the power on button, and let the Mac restart by itself
3. Login and get to the finder
4. Check "About this Mac". It should show that you're booting up automatically from the SSD.
Does it?
 
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Ben777

macrumors member
Jun 24, 2013
70
4
Just to inform you. Everything works great! Thanks!

Apps run much faster. It will take some time to get used to using "Macintosh HD" as "data only" (Documents, Music, Videos, Photos, etc.) drive, but other than that all seems amazing so far.

[doublepost=1545775107][/doublepost]Would you just delete apps from "macintosh HD" or let them stay there un-used? :)
 
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