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hewhore

macrumors member
Original poster
Jun 26, 2014
57
5
Germany
I just got a 2TB external SSD, primarily to download, and run, my Photos library on. I am now also considering installing macOS on it, as I have discovered a few applications whose installers take up considerably more space than is currently available on my M1 Mac mini's HD.
The last time I partitioned a drive was several years ago, to have the option to boot from different (Intel) Mac OS versions, so my memory is kind of hazy on what the criteria are for partitioning. My question is: Would it be advisable to create a partition to install Ventura or Sonoma on, seeing as I will want to have other file types hanging around on the new drive?
I already formatted the drive as Mac OS Extended (Journaled), but it seems that if it was formatted as APFS then partitioning is not relevant anyway?
 
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Ben J.

macrumors 6502a
Aug 29, 2019
571
281
Oslo
A few thoughts:

Installing macOS and booting the mac from an external drive is generally advised against. A few reasons, but the most obvious one is the possibility of the cable coming loose or failing in some way. The mac would immediately stop working, you'd lose any unsaved work and most likely there would be some corruption of data, OS or other.

There is no reason to use HFS+ (Mac OS Extended Journaled) on modern macs. And APFS has many advantages; the biggest one being that it uses "volumes". You typically don't create partitions anymore, you create volumes on APFS. Greatest thing about them is that you don't have to set a size on a volume. So you can create as many as you want, and they all share the free space on the disk, and they grow as needed.

You can still create partitions, and they must have their sizes set. One typical scenario; I have an external disk that I have one APFS partition on, and one with EXFAT format so that I can use it on Windows PCs.

Many people choose to save money by getting a small internal drive and bying the cheaper external storage from other than Apple. I've run macs the last few years with internals as small as 256 and 128GB and it's perfectly doable. Basically, you have macOS, user folder, and applications on the internal, and move big folders like video, photos etc to the external. You might then use symlinks (aliases) where those folders used to reside. Often, apps simply ask you to locate the folder when they can't find it where it used to be.

Be aware that your user folder is somewhat 'special', as it is in a way part of the system; macOS expects a user folder to contain certain folders, like Documents, Photos, and so on; the little graphic on the folder icon is an indication of this. So, if macOS suddenly doesn't find one of those folders, it might create a new one, and things can get messy, fast. So if you want to slim down some of these folders, you can move their content to an external drive, and replace them with aliases, that's fine.

Just make sure you get a proper Thunderbolt external drive for best performance. If the drive you have now is USB-C or USB 3, it might be only 10-30% the speed of Thunderbolt. You could consider keeping it, and using it for backup, and getting a Thunderbolt drive too.

I use Lightroom (not Photos) and I have my images on an external TB drive, so I'll leave it to the experts to say how best to move your photos from the user folder.
 
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hewhore

macrumors member
Original poster
Jun 26, 2014
57
5
Germany
I'm not planning on running macOS on the external drive as my daily driver, it's really only to install some large apps, a couple of games etc., I'm not going to be doing any video editing or similar high bandwidth workflows, so I'm not bothered about the lack of Thunderbolt. So from your answer, it seems that with the external SSD formatted as APFS, running a second iteration of macOS and (for example) my Photos library on the same drive will not be an issue.
 

rin67630

macrumors regular
Apr 24, 2022
229
125
A few thoughts:

Installing macOS and booting the mac from an external drive is generally advised against.
"generally advised against"? Who from? Just at the opposite !

I will always warmly recommend that everybody blessed with an Intel Mac has at least one bootable backup macOS partition. At best one "vanilla", without much changes to the standard.

And having another partition with the installer of the used macOS can later be a life saver.
A USB stick with the installer can do too, but is ways slower.
Don't rely on the internet recovery beside the fact that it is damn slow, experience tells that Apple cuts the wire without warning, and then?

And -last but not least- those, who have bought iMacs with only a HDD inside will largely benefit from running macOS over a USB3 external SSD.
 

rin67630

macrumors regular
Apr 24, 2022
229
125
So the question remains, should I partition or not?
If your SSD is currently formatted hfs+ and you want to run macOS beyond Mojave you MUST re-partition at least a portion of it as APFS. That is not hard to do, just might take a while if your HDD has data.
 

winxmac

macrumors 6502a
Sep 1, 2021
981
1,197
If your SSD is currently formatted hfs+ and you want to run macOS beyond Mojave you MUST re-partition at least a portion of it as APFS. That is not hard to do, just might take a while if your HDD has data.
No need to... Mojave and newer will automatically convert HFS+ to APFS during install... I think High Sierra also performs automatic file system conversion but not entirely sure...

I have partitioned the internal drive of my MacBook Pro 2015 when I dual booted Catalina and Monterey even though both uses APFS... Now, I am dual booting Catalina and Windows 10...
 

rin67630

macrumors regular
Apr 24, 2022
229
125
No need to... Mojave and newer will automatically convert HFS+ to APFS during install... I think High Sierra also performs automatic file system conversion but not entirely sure...
But do you really want to have your whole external SSD converted to APFS?
HFS+ is still one of the most compatible file system for user data.
 

winxmac

macrumors 6502a
Sep 1, 2021
981
1,197
But do you really want to have your whole external SSD converted to APFS?
HFS+ is still one of the most compatible file system for user data.
It depends on how I will use the disk... If I were to perform multi-boot and use it as a data disk at the same time, the file system will depend on what macOS version I am going to use...

Yes, for a partition that will be accessed by multiple macOS versions, HFS+ is the recommended option [if you will use macOS Sierra or older and macOS High Sierra or newer]... Now, as to what file system to use should it be used as boot drive and data disk, I will partition it first and leave the file system selection to the macOS version I will use... Of course, macOS Sierra and older can only use HFS+ although macOS Sierra had beta support for APFS if I remember correctly...
 

Fishrrman

macrumors Penryn
Feb 20, 2009
28,138
12,296
BenJ wrote:
"Installing macOS and booting the mac from an external drive is generally advised against"

It depends on the Mac.
I've booted and run my 2012 Mini from an external SSD from the day I took it out of the box in 2013. It ran far better that way than from the internal platter-based HDD. It's STILL running (from an external SSD) over on "the back table" when needed.

Having said that, you're correct that the OP will probably do better by booting the Mini from the internal SSD. Primarily because the internal drive is faster than most (not "all", but most) external SSDs that could be connected.

OP:
What SIZE is your internal SSD?

If it's "on the small side" (256gb), you should set things up this way:
On the internal drive:
- OS
- applications
- accounts (basic)
...and not much more.

By "basic" accounts, I mean that you move your "large libraries" such as movies, music and photos to an EXTERNAL drive, and access them from there. Your apps should have no trouble doing this.

On the external drive:
- data files
- movies
- music
- photo libraries
- etc.

What you MIGHT do with the external drive.
If you want to partition it, do so.
Keep one partition exclusively for photos
Use the other partition as "general external storage" -- for just that, data that won't fit on the internal, installers, etc.

BUT REMEMBER:
If you start using an external drive for "primary external storage", this means you have now added an ADDITIONAL drive volume that may also need to be BACKED UP.
 

bzgnyc2

macrumors member
Dec 8, 2023
60
90
I just got a 2TB external SSD, primarily to download, and run, my Photos library on. I am now also considering installing macOS on it, as I have discovered a few applications whose installers take up considerably more space than is currently available on my M1 Mac mini's HD.
The last time I partitioned a drive was several years ago, to have the option to boot from different (Intel) Mac OS versions, so my memory is kind of hazy on what the criteria are for partitioning. My question is: Would it be advisable to create a partition to install Ventura or Sonoma on, seeing as I will want to have other file types hanging around on the new drive?
I already formatted the drive as Mac OS Extended (Journaled), but it seems that if it was formatted as APFS then partitioning is not relevant anyway?

I normally partition my system/internal disk for my computers as well as family whose computers I assist. Additionally I sometimes partition external disks depending on what it is for/how it will be used.

I've been partitioning my system disks since my PowerBook G4/MacOS X 10.1 days which itself is probably a holdover from UNIX system administration days. Some of the reasons no longer apply but I still have my reasons.

Then you're correct that if you format a drive APFS then you can create multiple volumes on it without creating multiple partitions and it has the advantage that those volumes can all share the free space, avoiding the need to manage partition sizes and try to grow and shrink partitions. However, the volumes in an APFS container must all be APFS so you still need partitions if you need multiple filesystem types (e.g. one APFS and one exFAT). Additionally, partitions force separation. I don't know what new versions of MacOS will do to my system volume and the data on it during upgrades but I assume it will leave other partitions alone.

In any case, for any recent version of MacOS, you'll be using APFS for the system and it is generally recommended to use APFS over HFS+ on all flash/SSD storage. Although unlikely relevant in your case, spinning hard drives should not use APFS and so stick with HFS+ for Mac usage. For external drives that you might or plan to use to share data with non-Mac systems, exFAT will give you the best compatibility. For example, if you ever had to print something from a USB stick at a Fedex/Kinkos, those printer/copiers won't see an HFS+ or APFS partition last time I used one.

For the internal disk, I typically have 2-4 partitions: two to handle different OS versions, if a laptop then one to keep my home directory separate from a particular OS version, one for Bootcamp/etc.

For external disks (e.g. SSD), it depends. For simplicity's sake for an SSD that you will only use with Macs and won't be running the OS, one large partition as APFS should be fine. Then my Mac mini, I point my home directory to a folder on that drive so that I am not dependent on a drive soldered into the hardware. Plus I deliberately purchased the smallest internal drive available so that I could buy extra storage at market prices rather than Apple prices and replace that storage with a large drive anytime I wanted.

If your OS + applications + personal data is exceeding your internal drive, you could move your OS to an external drive as noted elsewhere but it's not ideal for reasons mentioned elsewhere. Among others you don't eliminate the dependency on the internal drive for system operation and performance is likely lower (though everything is so fast these days it may not be noticeable). On the flip side we've seen the continued shift towards applications that must install to /Applications (plus only installing as an administrator even though that's rarely necessary) which means your system drive/partition has to be pretty big, which is the problem I'm guessing you're having.

If your OS + applications is comfortably less than your internal drive (I'm guessing at least 256GB?), I would move your entire home folder, etc to the external drive before trying to run the OS + applications from an external. Also if you have applications that don't have to be in /Applications, you can keep those in your home directory (~/Applications), too. I haven't run into any problems keeping my home folder on an external disk while maintaining a symbolic link from /Users/login -> /Volumes/externaldrive/login (in theory you can just tell the system to maintain your account in a non-standard location in Users & Groups but I didn't find this reliable under much older OS and applications and haven't tried again recently). Assuming a 256GB internal drive and 60GB for macOS (base + room for system updates + room for bloat), are your applications (not counting their data) more than 150 GB?
 

bzgnyc2

macrumors member
Dec 8, 2023
60
90
So the question remains, should I partition or not?

I'm still not certain why you want to put your OS on the external SSD. Depending it may do what you want but there may be simpler solutions.

If you want to create a separate OS environment (i.e. independent version, configuration, etc) then putting that on the external drive to occasionally boot may be the way to go. If that is the goal then I would probably partition the external drive with the OS separate from my user files so that macOS can do whatever it wants in its partition and shouldn't mess with my data partition during upgrades, etc.

However, if the goal isn't so much creating a separate OS environment as managing space, I would look to keep the OS and applications on the internal drive and keep all my data on the external drive as per other post. If no need for other filesystems, etc on the external drive, I would probably keep it as one APFS partition.
 

picpicmac

macrumors 6502a
Aug 10, 2023
906
1,177
A few reasons, but the most obvious one is the possibility of the cable coming loose or failing in some way.
In all my years of using an external boot drive, I have never had a cable become unattached randomly.

There is no reason to use HFS+ (Mac OS Extended Journaled) on modern macs.
Unless it is a portable drive that one will connect to an older Mac.
 
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picpicmac

macrumors 6502a
Aug 10, 2023
906
1,177
If you want to create a separate OS environment (i.e. independent version, configuration, etc) then putting that on the external drive to occasionally boot may be the way to go.
This is what I will do on my next Mac.

It is my opinion that it is best to have more than one version of the operating system from which one can boot.

I wish to keep my Macs for many years. As such they go through several OS iterations.

Even with the current architecture of having the internal SSD contain necessary information that once was held in the PRAM or some other memory, I will want to keep separate environments for each major OS change.

And external TB enclosures are fast enough to not notice the difference in speed.
 

rin67630

macrumors regular
Apr 24, 2022
229
125
It is my opinion that it is best to have more than one version of the operating system from which one can boot.
It's also highly advisable to have two backup versions of your current OS on an external drive.
-One full backup that you can use un case of problems with your main drive (a life saver)
-A "vanilla" version of macOS wher you made as less modifications as possible, to check software problems.
 

chabig

macrumors G4
Sep 6, 2002
11,129
8,811
It's also highly advisable to have two backup versions of your current OS on an external drive.
-One full backup that you can use un case of problems with your main drive (a life saver)
-A "vanilla" version of macOS wher you made as less modifications as possible, to check software problems.
I disagree on this point. It used to be true, not no longer. This is what macOS Recovery is for.

 

chabig

macrumors G4
Sep 6, 2002
11,129
8,811
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picpicmac

macrumors 6502a
Aug 10, 2023
906
1,177
Apple Silicon?
It's because current Macs do not have separate PRAMs or other memory holding the system info. The NAND chip that hosts the internal macOS SSD also stores all the necessary start-up data. So even if one has an external storage with a start-up installation of macOS, the internal NAND is needed initially before the rest of the boot sequence switches to reading the external macOS.
 
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rin67630

macrumors regular
Apr 24, 2022
229
125
It's because current Macs do not have separate PRAMs or other memory holding the system info. The NAND chip that hosts the internal macOS SSD also stores all the necessary start-up data. So even if one has an external storage with a start-up installation of macOS, the internal NAND is needed initially before the rest of the boot sequence switches to reading the external macOS.
That is exactly why i will never buy an Apple silicon Mac.
The nand chip are wearing. Once defective you can ditch your Mac.
 

picpicmac

macrumors 6502a
Aug 10, 2023
906
1,177
The nand chip are wearing.
Not as much as fear mongers are pushing.

Of course Apple is not intending on selling computers all of which will last 30 years.

Amortization of desktops is 5 years for business. A home user could shoot for 10 years of use.

It's unlikely that 20 years of use will occur with current generation of computing devices.

This is, intended or not, roughly equivalent to a lifetime of an automobile is normal USA use. 10 years is about it for a commuting car. Somewhere between 150k and 200k miles is about it for an auto before it's just too much trouble to keep running.
 
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rin67630

macrumors regular
Apr 24, 2022
229
125
Not as much as fear mongers are pushing.
Of course Apple is not intending on selling computers all of which will last 30 years.
Nobody has enough distance to evaluate it.
Basically it should be a no-go to include a notorious wearing element as non replaceable.
Would you buy a car where the brakes are not replaceable?
I want to decide myself how much effort I put into to keep it running and not be incapacitated by the vendor.
 
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