What's the minimum size SSD recommended to run macOS Mojave on?

[ipedro]

I have an iMac (late 2012) with a Fusion Drive comprised of a 128GB SSD and a 1TB HDD.

The SSD portion was failing or at least the "fusion" relationship between them was. I managed to split the drives into their own individual selves and the SSD seems to be working just fine on its own even though it's marked with a S.M.A.R.T. error.

I installed Mojave on the HDD and it works but it's slow given that it's a spinning drive. I'm considering running the operating system on the 128GB SSD and using the 1TB for file storage.

Is 128GB enough to run macOS and apps comfortably, including virtual memory?

 

[crjackson2134]

Is 128GB enough to run macOS and apps comfortably, including virtual memory?

It can be done if you don't have a lot of Apps, but not what I'd call comfortably. That's a little tight for my taste, but you may be light on Apps compared to me. Give it a whirl and see what happens. It's certainly enough for just the OS files.

 

[saudor]

definitely possible if you tinker around (i.e. move your iOS backups using symlinks to another drive, moving itunes library elsewhere, etc)

 

[ipedro]

definitely possible if you tinker around (i.e. move your iOS backups using symlinks to another drive, moving itunes library elsewhere, etc)

I don’t ever plug my iOS devices into my Mac. Backups are on iCloud.

Actually, almost all of my files are on iCloud. I subscribe to the 2TB plan. I have folders for personal files and work files on there. The problem I foresee is that macOS tends to pull iCloud files down into local storage, even if they’re not in use. I wonder if it would be smart enough to keep a nice large buffer or if I could manually keep all my files on iCloud and only download them as needed.

Would it be viable to install apps on the HDD while macOS runs on the SSD? The main apps that I use are Lightroom, Photoshop, Illustrator and Final Cut Pro X. Together, they come up to under 10GB, though their temporary background files may be higher than that.

How much real storage does macOS Mojave need to run? My iMac has 24GB of RAM but some of the apps I use eat it up quickly and resort to virtual memory on disk.

 

[TETENAL]

You can get a new SSD installed into your iMac for not too much money. I don't think it's a good idea to run off a drive that's marked with a S.M.A.R.T. error.

 

[Steeley]

I've been using a 128GB drive for years, it's definitely feasible. I still have 51GB free.

I'm running the latest Mojave beta and have about 80 apps installed including the MS Office suite and the Affinity suite.

I use iCloud Drive (though still most things are on the local drive even with that), and I stream movies and music.

 

[saudor]

I don’t ever plug my iOS devices into my Mac. Backups are on iCloud.

Actually, almost all of my files are on iCloud. I subscribe to the 2TB plan. I have folders for personal files and work files on there. The problem I foresee is that macOS tends to pull iCloud files down into local storage, even if they’re not in use. I wonder if it would be smart enough to keep a nice large buffer or if I could manually keep all my files on iCloud and only download them as needed.

Would it be viable to install apps on the HDD while macOS runs on the SSD? The main apps that I use are Lightroom, Photoshop, Illustrator and Final Cut Pro X. Together, they come up to under 10GB, though their temporary background files may be higher than that.

How much real storage does macOS Mojave need to run? My iMac has 24GB of RAM but some of the apps I use eat it up quickly and resort to virtual memory on disk.

I have a clean install of macOS mojave and it's about 9gb. I do have the sleepimage disabled though (which is about the size of your RAM) I think you'll be fine though. When i was editing a 1gb photoshop file, photoshop gobbled up 30 gb of scratch disk space which is still under the 128gb

Not sure about how iCloud handles things these days. My friend used to use iCloud drive on their 16gb iPad a couples years back. That ipad was always 0 bytes free and had troubles downloading despite the entirety of the data being on the cloud.

The bigger issue is the failing SSD but as long as you know what you're getting into and keep backups, maybe you'll be ok .

 

[ipedro]

You can get a new SSD installed into your iMac for not too much money. I don't think it's a good idea to run off a drive that's marked with a S.M.A.R.T. error.

As I understand it, Apple won't upgrade my iMac for me. They'll reinstall a new drive to original factory specs. If I take it to a third party repair, they charge an insane amount of money to open up an iMac for the same reasons why I wouldn't do it myself. It's a laborious time consuming process.

I really just want to extend the life of my iMac by a couple of years at best. I'm waiting to see what happens with the iPad Pro. I'm convinced that Apple will release an iMac-like desktop iPad on an articulating arm. I already use iOS for work, pushing it to its limit. I don't want to buy another iMac if developing iOS to be fully featured is where Apple is headed as is the logical conclusion.

 

[matreya]

An alternative solution is to get a Samsung T5 external SSD which would connect via USB3... You can get them in sizes ranging from 250GB to 2TB.

 

[crjackson2134]

An alternative solution is to get a Samsung T5 external SSD which would connect via USB3... You can get them in sizes ranging from 250GB to 2TB.

This is a really good solution IMHO. Since OP is looking to preserve use of his iMac temporarily, without a wasted investment in repairs, this would represent a not only a solution but an investment that can be moved to a new system when the time arrives.

 

[Fishrrman]

My advice:

Can you use Disk Utility to erase the 128gb SSD?
Once erased, can you run "repair disk" on it?
What result do you get?

IF "repair disk" gives you "a good report", REPEAT the repair disk function 5 times in a row.
Do you get the good report each and every time?

If that's the case, I'd put the OS onto the SSD and "run it from there".

CAUTION:
A 128gb SSD will easily "hold and run" the OS along with your apps.
You should put your account on it, too, but...

... if you have "large libraries" of movies, music and pics -- "leave them behind" on the HDD.
They don't require "disk speed" for access. They just have to "be there".
The idea is to keep the SSD "lean and clean", and it will run at its best -- MUCH FASTER than trying to boot and run the OS from the HDD.

IF your copy of Mojave is running ok (even if it's "slow"), you could use CarbonCopyCloner to "clone it over" to the SSD.
IF you have those "large libraries" I mentioned above, you can "de-select" them in CCC and they will "stay where they are" (not clogging up the SSD).
CCC will also clone the recovery partition -- yes, you want to do this, too.

CCC is FREE to download and use for 30 days.
The process will go so quickly, you'll come back here and tell us "I can't believe that was so easy!"

 

[Weaselboy]

Is 128GB enough to run macOS and apps comfortably, including virtual memory?

Depending on how much data you have, 128GB is easily enough.

My MBP is my only computer and with the OS and apps, plus about 1GB in documents, about 10GB of music and 10GB of photos, I am using a total of 63GB in storage.

 

[Tarek]

A lot of people I know actually have 128 GB SSD MacBooks and they're quite fine with it, and most of them use external storage for backups and large data, so you should be fine. I'd try @Fishrrman's method in order to fix the error if possible, though, just for the stability and longevity of the drive and iMac.

 

[ipedro]

I’ve actually run Disk Utility’s repair many times and it never finds any issues. However, in system profiler, it shows a “Failing” S.M.A.R.T. Status.

I wouldn’t mind running macOS from it. Worse thing that would happen if the SSD fails is the machine crashes. All my files are stored on iCloud.

Still, I’d like to know how S.M.A.R.T. works. I know I had file system problems when running APFS on the Fusion Drive on High Sierra. I wonder if it triggered an error that has stayed on the drive even though there’s no physical problems. I mean, how can an SSD fail before the spinning disk?

 

[TETENAL]

If I take it to a third party repair, they charge an insane amount of money to open up an iMac for the same reasons why I wouldn't do it myself.

I don't know the situation in Canada or the US, but I looked up the prices in Germany and upgrading the SSD for your Mac is €190 for 250GB and €240 for 500GB including work. I don't think that's an insane amount of money.
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I’ve actually run Disk Utility’s repair many times and it never finds any issues. However, in system profiler, it shows a “Failing” S.M.A.R.T. Status.

Disk Utility's repair checks the status of the file system (the actual bits of how the file system is written on disk and its logical consistency). S.M.A.R.T. checks several (hardware) parameters of the drive. It can predict drive failures even when the actual stored data is not corrupted yet.