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2 TB Fusion costs $100 more than 256 GB Flash. I know someone in particular will strenuously disagree, but if you were going to spend the money to have 256 GB internal Flash, why not pop the extra $100 to have 8 times the internal storage? Sure, you're getting 128 GB Flash instead of 256 GB, but in practical application, the effectiveness of the Fusion caching scheme more than makes up for the smaller amount of Flash. (I'd love to see Apple's internal data on Fusion performance, though I have a feeling the results are, essentially, "We hit a point of rapidly diminishing returns at 128 GB" - if they had a performance-based reason for selling a "premium" Fusion with 256 GB Flash, don't you think they would?)

Now, the benchmarkers will say that all-Flash will be faster than Fusion. However, since you seem willing to compromise raw speed by using a significantly slower external SSD, "compromising" on Fusion vs. internal pure-Flash doesn't seem all that bad. I'd make a small wager that the Fusion drive will beat the performance of that external SSD, or come very close to matching.

OK, I'm a Fusion "true believer." It works really well for me. As I've said before, I have one late 2013 iMac running on pure Flash, another late 2013 iMac running on Fusion, and in day-to-day use, it's very hard to tell their performance apart. There's more than enough Flash in the Fusion drive, apparently, to have nearly everything I do running on Flash - apps, OS, and data alike.

But if you're happy running on the external (we ran a business-critical Cube on an external drive for about 5 years after the internal failed)... yeah, you haven't missed any points. I like Fishrrman's suggestion to fasten that external drive to the machine - I'd also anchor the USB (or TB) cable to the machine in some way, too - anything that would help avoid accidental disconnects - if the Mac moves, the drive and cable should move with it.
 
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2 TB Fusion costs $100 more than 256 GB Flash. I know someone in particular will strenuously disagree, but if you were going to spend the money to have 256 GB internal Flash, why not pop the extra $100 to have 8 times the internal storage? Sure, you're getting 128 GB Flash instead of 256 GB, but in practical application, the effectiveness of the Fusion caching scheme more than makes up for the smaller amount of Flash. (I'd love to see Apple's internal data on Fusion performance, though I have a feeling the results are, essentially, "We hit a point of rapidly diminishing returns at 128 GB" - if they had a performance-based reason for selling a "premium" Fusion with 256 GB Flash, don't you think they would?)

Now, the benchmarkers will say that all-Flash will be faster than Fusion. However, since you seem willing to compromise raw speed by using a significantly slower external SSD, "compromising" on Fusion vs. internal pure-Flash doesn't seem all that bad. I'd make a small wager that the Fusion drive will beat the performance of that external SSD, or come very close to matching.

OK, I'm a Fusion "true believer." It works really well for me. As I've said before, I have one late 2013 iMac running on pure Flash, another late 2013 iMac running on Fusion, and in day-to-day use, it's very hard to tell their performance apart. There's more than enough Flash in the Fusion drive, apparently, to have nearly everything I do running on Flash - apps, OS, and data alike.

But if you're happy running on the external (we ran a business-critical Cube on an external drive for about 5 years after the internal failed)... yeah, you haven't missed any points. I like Fishrrman's suggestion to fasten that external drive to the machine - I'd also anchor the USB (or TB) cable to the machine in some way, too - anything that would help avoid accidental disconnects - if the Mac moves, the drive and cable should move with it.

Still on the fence. I bought a Thunderbolt External SSD Drive so I will clone the drives later and see if there's any difference.
 
Since I'm still a week into my return period, I could just return this iMac and preorder a 256GB SSD but the seemed like a cheaper solution.
if it was me, I'd return it. These machines are just too expensive to accept a configuration that doesn't work well.
 
inferno wrote:
"I bought a Thunderbolt External SSD Drive so I will clone the drives later and see if there's any difference."

Please post the read/write numbers for the external USB3 vs. the external thunderbolt....
 
inferno wrote:
"I bought a Thunderbolt External SSD Drive so I will clone the drives later and see if there's any difference."

Please post the read/write numbers for the external USB3 vs. the external thunderbolt....

Honestly the numbers weren't all that different. I've already packed up the iMac and am going back to the Apple Store today to do the exchange otherwise I'd post those screenshots.

The boot process with the Thunderbolt drive was surprisingly slower than the USB3 device but while the speed was better, I (like most in this thread) think having an actual internal SSD will be much much faster.

Thanks for the advice all...
 
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Honestly the numbers weren't all that different. I've already packed up the iMac and am going back to the Apple Store today to do the exchange otherwise I'd post those screenshots.

The boot process with the Thunderbolt drive was surprisingly slower than the USB3 device but while the speed was better, I (like most in this thread) think having an actual internal SSD will be much much faster.

Thanks for the advice all...

Exchange complete.. My new iMac won't be here until next Wednesday. I hope Apple doesn't come out with a new model in the meantime.
 
Honestly the numbers weren't all that different. I've already packed up the iMac and am going back to the Apple Store today to do the exchange otherwise I'd post those screenshots.
I think that's probably the best solution :)
 
Post your impression of performance based on internal HDD, externals SSD and the new internal SSD once you get it all set up.
 
I bought a iMac in 2013 that has an 256 GB internal SSD. Obviously not enough. I have 5 external drives for various things (Thunderbolt and a couple USB 3). I have never ever had a problem with any of them running this way. The only thing that sometimes happens is on boot-up, some of the drives don't show up on the desktop, although they are in fact mounted (I suspect that the system polls for the drives before they are fully initialized). When this happens, it's solved with a simple Option+Control Click on the Finder icon to relaunch it.

I used symbolic linking to put all my various folders (Documents, Movies, Photos, etc.) on the other drives. The only thing I have running on the internal SSD are my apps. I even have a Windows Boot Camp partition on one of the externals (that was a little annoying to set up, but once done works flawlessly).
 
I bought a iMac in 2013 that has an 256 GB internal SSD. Obviously not enough. I have 5 external drives for various things (Thunderbolt and a couple USB 3). I have never ever had a problem with any of them running this way. The only thing that sometimes happens is on boot-up, some of the drives don't show up on the desktop, although they are in fact mounted (I suspect that the system polls for the drives before they are fully initialized). When this happens, it's solved with a simple Option+Control Click on the Finder icon to relaunch it.

I used symbolic linking to put all my various folders (Documents, Movies, Photos, etc.) on the other drives. The only thing I have running on the internal SSD are my apps. I even have a Windows Boot Camp partition on one of the externals (that was a little annoying to set up, but once done works flawlessly).

I've contemplated the external Windows boot SSD when I get my replacement iMac. Any quick links on how to set one of these up?
 
I've contemplated the external Windows boot SSD when I get my replacement iMac. Any quick links on how to set one of these up?

Honestly I can't remember the details of how I did it now. I just know that Windows was very resistant to being installed on an external, and there was some trick to it. These guys talk about a method on an Apple discussion board. I can't remember exactly how I did it, but I can say that if I managed, it probably wasn't too hard.
 
Honestly I can't remember the details of how I did it now. I just know that Windows was very resistant to being installed on an external, and there was some trick to it. These guys talk about a method on an Apple discussion board. I can't remember exactly how I did it, but I can say that if I managed, it probably wasn't too hard.

Thx!
 
Update: I got the replacement iMac early and you guys were right. The PCIe SSD is blazing fast. Much better that the external drive idea. Thanks for the push!!!
 
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I'd return the iMac and buy one with an internal SSD. Like others have said you sometimes have external drives disconnecting - this would be incredibly frustrating if that was your boot drive. Save yourself all the hassle and just swap the machine.
 
I'd return the iMac and buy one with an internal SSD. Like others have said you sometimes have external drives disconnecting - this would be incredibly frustrating if that was your boot drive. Save yourself all the hassle and just swap the machine.
He did ;)

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Update: I got the replacement iMac early and you guys were right. The PCIe SSD is blazing fast. Much better that the external drive idea. Thanks for the push!!!
 
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