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mmackinven

macrumors newbie
Original poster
Jun 28, 2011
10
4
Auckland
Hey, I have a 2017 iMac with 2tb fusion drive, and looking at using an external SSD to run the OSX/Apps etc off.

My 2013 MacBook Pro is being replaced by Insurance, and they're sending me the 512gb SSD from it – would this work fine in a USB-C enclosure and used with the iMac?

As for the 2tb fusion drive, can this be partitioned 50/50 then used as a backup and extra space drive?
Or should I just use it as spare space?

Will I notice much of a difference in speed? I have the 4.2Ghz model with 40GB ram.
 

Fishrrman

macrumors Penryn
Feb 20, 2009
28,596
12,713
Before you do anything else, get the 512gb SSD "in hand".
Then, see if you can find an external enclosure that will fit it.

It's not a standard 2.5" SSD -- it's an Apple custom designed SSD/blade drive.

If you can get an enclosure for it, then do some "speed testing" before you commit to it.
You may find that the internal SSD on the iMac is FASTER THAN the older (but larger) 512gb SSD.

If I wanted the full speed that the 128gb SSD of the iMac fusion drive could deliver, I'd do this:
1. Backup the fusion drive
2. Use terminal to "split" the fusion drive into standalone 128gb SSD and 2tb HDD
3. Install the OS onto the SSD
4. Install my apps and [basic] accounts onto the SSD
5. Let the large libraries of movies, music and pictures stay on the HDD.

The iMac's SSD will then run "at full speed, all the time".
Keep it "lean and clean" and it should be a fine performer for its service life.
NO WAY you're going to get equivalent speeds running from ANY externally-connected SSD...
 
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mmackinven

macrumors newbie
Original poster
Jun 28, 2011
10
4
Auckland
Before you do anything else, get the 512gb SSD "in hand".
Then, see if you can find an external enclosure that will fit it.

It's not a standard 2.5" SSD -- it's an Apple custom designed SSD/blade drive.

If you can get an enclosure for it, then do some "speed testing" before you commit to it.
You may find that the internal SSD on the iMac is FASTER THAN the older (but larger) 512gb SSD.

If I wanted the full speed that the 128gb SSD of the iMac fusion drive could deliver, I'd do this:
1. Backup the fusion drive
2. Use terminal to "split" the fusion drive into standalone 128gb SSD and 2tb HDD
3. Install the OS onto the SSD
4. Install my apps and [basic] accounts onto the SSD
5. Let the large libraries of movies, music and pictures stay on the HDD.

The iMac's SSD will then run "at full speed, all the time".
Keep it "lean and clean" and it should be a fine performer for its service life.
NO WAY you're going to get equivalent speeds running from ANY externally-connected SSD...

Thank you!

The write speed of the rMBP SSD is around 7-800MB/s, I can't seem to find the speed of the 128GB SSD of the Fusion drive anywhere :/

Splitting the Fusion drive, will that make a noticeable difference?

I use my iMac for high end Retouching, Photography and Design, and also a bit of 4K video/timelapse editing – would I benefit more with just adding the 512GB SSD as an external scratch disk instead maybe?
 

Fishrrman

macrumors Penryn
Feb 20, 2009
28,596
12,713
"I use my iMac for high end Retouching, Photography and Design, and also a bit of 4K video/timelapse editing – would I benefit more with just adding the 512GB SSD as an external scratch disk instead maybe?"

That would probably work quite well.
"Split" the internal fusion drive into 2 standalone drives.
Put the OS, apps, and basic account on the internal 128gb SSD -- it will run FAST.
Keep your work files on an external USB3 SSD, for speed.

BUT AGAIN -- the question remains:
Can you find an enclosure that will take an Apple-OEM drive?
 

awer25

macrumors 65816
Apr 30, 2011
1,100
327
Thank you!

The write speed of the rMBP SSD is around 7-800MB/s, I can't seem to find the speed of the 128GB SSD of the Fusion drive anywhere :/

Splitting the Fusion drive, will that make a noticeable difference?

I use my iMac for high end Retouching, Photography and Design, and also a bit of 4K video/timelapse editing – would I benefit more with just adding the 512GB SSD as an external scratch disk instead maybe?

I have a 2017 iMac too (5K model) but with the 1TB Fusion and wanted to do the same, since I didn't realize that the 1TB Fusion is only a 24 or 32GB SSD. Short answer is just sell the SSD and use the iMac as is (or upgrade the internal SSD).

I tried a Samsung 2.5" 512GB SSD in a USB 3.1 Gen 2 enclosure with proper USB-C cable and while it was generally fine, there were hiccups, times when the system would freeze for a few seconds, etc. It wasn't really that good as the main drive. I then bought a 512GB SSD to install, but didn't realize the new 2017 iMacs (at least the 5K version) use a completely different NVMe SSD (SSPOLARIS). The previous generation SSDs from 2015-16 (SSUBX) do fit, but don't boot - trust me I tried.

These new NVMe drives in your iMac are extremely fast, and from what I understand are basically Samsung 960 Pro drives (~3500MB/s read, ~2100MB/s write). I ended up replacing the 1TB HDD with the Samsung 2.5" SSD, and created a Fusion drive out of the small Apple SSD and the Samsung 2.5" one.

Therefore, your 2TB Fusion has an extremely fast 128GB NVMe SSD, and I think you should try it first since 128GB is actually fine for most people. I don't even think there is an enclosure for your Apple SSD from the MacBook. In any case, you won't like booting from a USB drive, even USB 3.1 Gen 2. If you really want more SSD space, I'd ideally buy an Apple NVMe SSD from eBay (make sure the label says SSPOLARIS) and an install kit from iFixit and just upgrade what you have. If you want to save some money, you can also replace the HDD with a regular 2.5" SSD.

Feel free to reach out if you want more help.
 
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pier

macrumors 6502a
Feb 7, 2009
579
950
Hey, I have a 2017 iMac with 2tb fusion drive, and looking at using an external SSD to run the OSX/Apps etc off.

My 2013 MacBook Pro is being replaced by Insurance, and they're sending me the 512gb SSD from it – would this work fine in a USB-C enclosure and used with the iMac?

As for the 2tb fusion drive, can this be partitioned 50/50 then used as a backup and extra space drive?
Or should I just use it as spare space?

Will I notice much of a difference in speed? I have the 4.2Ghz model with 40GB ram.

Even at SATA SSD speeds (around 4-500MB/s) you should notice a speed increase over Fusion.

If you've been happy with Fusion, a simple USB 3 case should be more than enough. Whether the cable connector is USB-C or USB-A doesn't matter.

In theory you could use a Thunderbolt 3 case if you needed more speed, but haven't found one for the Apple SSDs.
 

mmackinven

macrumors newbie
Original poster
Jun 28, 2011
10
4
Auckland

I ended up buying one of these! However turns out the R/W speed of my MBPr 500GB SSD is around 280MB/s, a bit slower than the 7-800MB/s for the current fusion drive.

I have an option to purchase a 1TB SSD, M.2 (2280), NVMe, R/W(Max) 3,400MB/s/2,500MB/s for a good price, would this be a worthy upgrade?
 

awer25

macrumors 65816
Apr 30, 2011
1,100
327
I ended up buying one of these! However turns out the R/W speed of my MBPr 500GB SSD is around 280MB/s, a bit slower than the 7-800MB/s for the current fusion drive.

I have an option to purchase a 1TB SSD, M.2 (2280), NVMe, R/W(Max) 3,400MB/s/2,500MB/s for a good price, would this be a worthy upgrade?
Is it an Apple SSD? If not, it won’t work in the iMac. Or do you mean to upgrade the enclosure?
 

tubeexperience

macrumors 68040
Feb 17, 2016
3,192
3,897
Do you have an Early 2013 or Late 2013 MacBook Pro?

If you have a Late 2013, you can install the SSD from that into your iMac.
 

awer25

macrumors 65816
Apr 30, 2011
1,100
327
Do you have an Early 2013 or Late 2013 MacBook Pro?

If you have a Late 2013, you can install the SSD from that into your iMac.
OP said he had a 2017 iMac which only takes 2017 SSDs (NVMe SSPOLARIS drives). I thought the same as you but even though the earlier SSDs fit, they aren't recognized by the computer.
 

tubeexperience

macrumors 68040
Feb 17, 2016
3,192
3,897
OP said he had a 2017 iMac which only takes 2017 SSDs (NVMe SSPOLARIS drives). I thought the same as you but even though the earlier SSDs fit, they aren't recognized by the computer.

Late 2013 MacBook Pro has AHCI SSD which is compatible.

Early 2013 MacBook Pro has SATA SSD which is not compatible.
 

awer25

macrumors 65816
Apr 30, 2011
1,100
327
NVMe is backwards compatible

Any computer that supports NVMe SSDs also support AHCI SSDs.
On a PC that is correct, but from what I was able to tell from my own experimenting it doesn't seem to be the case on an Apple. You can see my initial post on this thread for the details, but I tried everything to get a 2015 SSD (AHCI) to be recognized in my 2017 iMac and it was not, not even in recovery mode. Every screen acted like there was no SSD present, just the 1TB HDD.

I could be wrong, but I really tried
 

tubeexperience

macrumors 68040
Feb 17, 2016
3,192
3,897
On a PC that is correct, but from what I was able to tell from my own experimenting it doesn't seem to be the case on an Apple. You can see my initial post on this thread for the details, but I tried everything to get a 2015 SSD (AHCI) to be recognized in my 2017 iMac and it was not, not even in recovery mode. Every screen acted like there was no SSD present, just the 1TB HDD.

I could be wrong, but I really tried

Hm, I would try, but I don't have a 2017 iMac.
 
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