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iMac 1 TB Fusion Drives Have Smaller SSDs

While I was at MacTech Pro in New York City recently, I learned an interesting fact while chatting with one of the consultants in attendance. When you buy a 2017 iMac — either the 21.5-inch model or the 27-inch model — you can configure it with a 1 TB Fusion Drive for storage, but the hardware specs of that particular drive might give you pause.

Apple’s Fusion Drive combines hard disk and SSD storage in a drive that appears to the operating system as a single volume. Hard disks provide a lot of storage for a low cost per gigabyte, but they’re relatively slow. SSDs — solid-state drives — are much faster but can cost over 5 times more per gigabyte. By fusing the hard disk and SSD into a single volume, a Fusion Drive provides a lot more storage than an SSD with far better performance than a hard disk. macOS achieves this performance by storing operating system files, commonly used apps, and your most frequently used data on the SSD. Adjusting data storage locations happens behind the scenes, so you don’t (and can’t) know what data is stored where — some files may even be stored in both places.

Personally, I don’t need that much storage, so I stick with SSDs on my Macs, but the Fusion Drive is a good compromise for many iMac buyers.

I’d heard rumors that Apple had at some point reduced the amount of SSD storage in the 1 TB Fusion Drive, but I didn’t know where to confirm the amounts until hearing about it at MacTech Pro. Strangely, Apple doesn’t mention the sizes of the hard disk and SSD in the Fusion Drive on the Tech Specs page for the Macs that have it as an option (the iMac and the Mac mini). Instead, you can find the information only by configuring a Mac for purchase, and clicking the “How much storage is right for you?” link above the storage options. That displays a pop-up with the details.

There you’ll learn that, although the 1 TB Fusion Drive in the Mac mini includes a 1 TB hard disk and a 128 GB SSD, as did the original 1 TB Fusion Drive in the iMac, the 1 TB Fusion Drive you can purchase with any current iMac model includes only a 32 GB SSD. However, the 2 TB and 3 TB Fusion Drives available for the 27-inch iMac with Retina display both include 128 GB SSDs. Apple even recommends that iMacs with 32 GB of RAM be configured with at least a 2 TB Fusion Drive; I wonder if that’s due to temporary operating system files, such as virtual memory swap files and the file that stores the contents of memory when the Mac goes to sleep, taking up too high of a percentage of the SSD.

What I hadn’t realized before researching this article is that the 32 GB SSD in the current 1 TB Fusion Drive is actually an improvement because in 2015, Apple reduced the size of the SSD in the 1 TB Fusion Drive from the original 128 GB to just 24 GB.

Regardless, the practical upshot of this information is that I would encourage anyone considering an iMac to avoid the 1 TB Fusion Drive. Instead, you could spend an extra $100–$200 on a 256 GB SSD and get an inexpensive external hard disk to hold large amounts of data. Alternatively, you could pay an extra $200 or $300 and get either the 2 TB or 3 TB Fusion Drive.

Whatever you do, don’t get an iMac with just the 1 TB hard disk. I think it’s a big mistake to configure any Mac with just a hard disk these days because the Fusion Drive and particularly SSDs are so much faster. An SSD or Fusion Drive provides the most performance gain you can get for your buck.

Finally, Apple, why aren’t you listing these key details about the Fusion Drives on the actual Tech Specs page for these machines? It’s borderline deceptive to hide it behind a pop-up on the purchase page.


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Comments about iMac 1 TB Fusion Drives Have Smaller SSDs
(Comments are closed.)

Charles  2017-08-07 18:25
Now this might explain why I keep getting errors "out of application memory, close some apps." It has been driving me crazy. I have a new iMac18,3 with a 1TB Fusion Drive and I have 24GB of RAM in it (8 original plus 16). I never had this problem running out of memory using the same apps on my old 2011 Mac mini with a 512GB SSD and only 16GB RAM. Maybe I should pull the two 4GB SIMMs out, giving me only 16GB, then my application memory should fit totally within the 24GB SSD in my 1TB Fusion drive. That would be awful, having to pull good RAM to improve performance.
Adam Engst  An apple icon for a TidBITS Staffer 2017-08-07 18:08
That would be a freaky problem, but it doesn't sound unreasonable. :-(
Gary Schroeder  2017-08-07 18:25
I think it is a bit arrogant to say that everyone buying the new iMac should shell out an extra $200 or $300 to get a 2 or 3 terabyte hard drive just to get the bigger SSD. I would guess that most buyers of the new iMac aren't doing large, memory intensive work on their computers that would require them to have to install more than 16 or even 8 GB of RAM. Those who need more than 16 GB of RAM should get the bigger drive but I would think everyone else using less memory would do just fine with the 1TB drive. And save a few hundred bucks to boot.
Adam Engst  An apple icon for a TidBITS Staffer 2017-08-07 19:50
I just think it's a false economy. You can always save money by getting a slower and less powerful machine, but there are better and worse places to economize. In most situations, I'd recommend an SSD over a Fusion Drive anyway, but I was distressed to learn that the 1 TB Fusion Drive wouldn't even have the same performance boost as the 2 TB and 3 TB models.
frederico  2017-08-07 21:26
I don't think it's out of line to advise the best bang-for-the-buck options, that not only assure a reasonable (though not optimal) experience, but that also help maintain a resale value and long-term usability in a(n ostensibly) non-upgradeable machine.

If you're OK with the slowest possible experience out of the box, and later hanging an external SSD off the back in order to get the performance it should have shipped with, okay.

If you do the street-value math on HDD vs Fusion vs SSD BTO from Apple, it's, IMHO, pretty clear that Fusion is the best way to go when factoring in resale value. Apple SSD is so crazily overpriced I just couldn't stomach it. Yes, I will crack these brand new machines open in a few months and replace the HDD with a fat SSD at 2-3x the capacity for the BTO cost, plus keep the Fusion SSD in the bargain.

What's frustrating is that Apple's forcing any of us to even choose a 5900RPM, tiny HDD at all; it just ends up reflecting badly on them overall.
Charles  2017-08-07 22:40
I agree, it's worth knowing the most cost effective configs. I had to buy a stock off-the-shelf iMac since my computer died and I needed an immediate replacement to work my next online shift the next day. I really wanted the SSD upgrade but it was build-to-order and would have taken a week or more to deliver. I figure third-party SSDs for new iMacs will ship soon (or existing SSDs would work but just aren't tested with the new models yet). I would gladly throw in an aftermarket 1TB SSD, but I'd have an authorized service center install it, I wouldn't crack open an iMac myself.
frederico  2017-08-09 01:44
There are plenty of existing SSD that function perfectly with the new iMacs; no "testing" is required for industry standard drives and protocols.

If you want a single drive (~$320 for 1TB with enclosure on sale), just make sure you get a USB-C (Thunderbolt 3) drive, or a USB 3.1 gen 1 or gen 2 drive with a gen 1 or gen 2 cable.

If you want RAID for speed, I recommend something like the OWC Mercury Elite Pro Duo mini (~$60 bare on sale) and you can buy two matching SSD for the same price as one of twice the volume (e.g., 2x 512GB ~$280 or less vs. 1TB ~$280 or less).

And don't let the nervous Nellies warn you off RAID 0; just use your internal drive as clone (hourly, if you wish), and you'll be fine. I've not had a RAID failure in years with quality SSD drives. Reply if you want more details.
frederico  2017-08-07 21:13
My disgust lies in the fact Apple not only ships a ludicrously small capacity blade (with a street value of ~$12), but that they are *still* using a non-standard connector and custom PCB from Samsung, using identical (but slower) V-NAND found on any common M.2; further, they could have easily advanced to NVMe M.2, available up to 1TB, & king of the hill for speed. The iMac Pro had damn well better at least use M.2, and NVMe if it wants to claim cutting edge.

I get that iMac isn't meant to be user-upgraded, but for those past caring about warranty, it's criminal one can't simply crack it open and install an industry standard M.2 up to 980GB (and climbing); worse, even if you wanted to at least up the 32GB to 128GB, you're SOL, as no one makes them for aftermarket; you have to find a used Apple OEM module.

Apple doesn't like that I'm finally retiring a 2008 & 2010 iMac, upgraded w/6TB HDD *&* 512GB SSD each; but yes, I suckered for a 2TB Fusion in each 2017 27" 5K I just ordered.
Dave Devine  2017-08-08 00:51
Sh*t out of luck
Dennis B. Swaney  2017-08-07 22:17
The question should not be: "Finally, Apple, why aren’t you listing these key details about the Fusion Drives the actual Tech Specs page for these machines?"

Rather, it should be: Apple, why are you lying to, and ripping off, your customers?
Or, at minimum, add a preposition:

"why aren’t you listing these key details about the Fusion Drives the actual Tech Specs page for these machines" >>
"why aren’t you listing these key details about the Fusion Drives ON the actual Tech Specs page for these machines"
Adam Engst  An apple icon for a TidBITS Staffer 2017-08-08 09:27
Typo fixed, thanks!
Does anyone know why Fusion drives aren't offered for laptops? I could really do with a terabyte of storage in a MacBook Pro, but a 1TB SSD is really expensive. For many years, I was used to computers constantly getting better in pretty much every way, but the (rather premature?) move to SSDs really put an end to the trend towards more and cheaper storage.
Adam Engst  An apple icon for a TidBITS Staffer 2017-08-08 09:28
I presume it's because of the size. Not a lot of room in Apple's current laptops.
B. Jefferson Le Blanc  2017-08-09 19:23
While it isn't as efficient as a Fusion Drive, you can add an external SSD for less than you would pay Apple for a 1TB SSD in a laptop. There are plenty of files, including iTunes Libraries and Photo libraries that you can relocate to an external drive.

Of course what Apple is really aiming at with their small laptops is for people to use the new remote storage features of Sierra and High Sierra to get you to pay for an iCloud Drive account. It's a not-to-subtle way for them to create an after market income stream for their hardware. Personally I'd rather pay for a medium size SSD in a Mac laptop and an external drive and keep Apple's grabby little fingers out of my computer as much as possible.

All this hubbub makes me happy that I have an older 27" iMac with an original 120GB SSD in my 1.12TB Fusion Drive.

By the way, you can control to some extent what files are located on the SSD in a Fusion Drive by using iDefrag on the drive from time to time. In a full defrag iDefrag prioritizes system files to the front of the drive (on the SSD). Though it doesn't specify where the dividing line is between the SSD and the HDD, treating, as it does, the two as a single drive, it can insure system files are where they can be used most efficiently. This would be the case even on a regular HDD, as the internal tracks can be accessed faster than those further out. Back in the day Norton Disk Doctor provided the same kind or organization profiles but with even more options for various use scenarios.

If you have a decent budget and reliable Internet access, an iCloud Drive account might be OK. Everything seems to be moving to the cloud these days, from Adobe Creative Cloud to Office 360, and password security suites like Last Pass and now 1Password. Though most of these are aimed at business clients who can write off the expense on their taxes.

As for cracking open an iMac, DYI is risky and paying an expert to do it is expensive. Even so it might be cheaper than paying Apple for a large SSD. Meanwhile, as Adam suggests, just upgrading your Fusion Drive is probably the most cost effective way to go with a new iMac.

For myself, even though I have a 1TB fusion drive in my iMac, I keep most of my data on a 2TB external drive, with a 2TB backup—because, you know, sh*t happens.
David Weintraub  2017-08-08 00:10
I remember when I bought a 100 MEGABYTE drive.

128Gb is a lot of space. Maybe it’s not if you have a few dozen movies and tens of thousands of pictures and songs. But, this is the high performance side of the drive. You have a terabyte of total space.

I suspect that Apple is tuning the amount of SSD needed for fast performance vs. storage. The files stored on a fusion drive move around as the drive is used. Older files are archived on the platter. Operating System files move back and forth.

There’s a story told in Ecconomics classes of Henry Ford sending agents out to junk yards to find out how Model-Ts held up. The agents find that every part has a life time of ten years, but one part called the kingpin is in excellent shape. Ford weakened the kingpin because having it last longer than the rest of the car was a waste of money. I suspect that few people will be able to notice a mere 128Gb SSD in their 1Tb fusion drive.
Adam Engst  An apple icon for a TidBITS Staffer 2017-08-08 09:30
128 GB is good, it's the 32 GB SSD in the 1 TB Fusion Drive that's concerning, so much so that Apple explicitly recommends against it if you have or might later want 32 GB of RAM.
B. Jefferson Le Blanc  2017-08-09 19:30
There's no way a 32GB SSD is more efficient than a 128GB SSD. It's a real puzzle why Apple chose to go this way. There's certainly no advantage to users. What they get out of it is anybody's guess. The old saying applies, caveat emptor—buyer beware. If you think Apple won't screw you over, you're naive.
Alan Sanders  2017-08-08 01:09
This is not "borderline deceptive" at all! It is blatantly deceptive to sell a workhorse machine with a 1TB fusion drive that has only 32GB of SSD storage. 32GB is a pittance!

What's the problem?! Apple doesn't have enough billions to equip their mainstream desktop computer with storage options that don't cripple its performance? They did the same thing when they first introduced the super-thin iMac design. My 2010 iMac, which had a 7200rpm HD, was faster than my 2012 iMac, which had a 5400rpm drive that was clearly not up to the task of running the machine at its full potential. Making money is one thing, but living to make money is quite another! Compromising the quality of your products in order to make more money is disgusting! Years ago, I would never have believed that Apple would ever do that. But now here we are!
Renate Wesselingh  2017-08-08 05:06
That may explain why I was disappointed with the performance of the iMac with the 1TB Fusion Drive I got at my work in 2016. I would have thought that it would be a lot faster than my own 2015 MacBook Pro, but it was not. Was, because it was stolen two months ago.
I'll pay attention when I buy its successor, I'll happily shell out a bit more money from my work account if that can guarantee faster reaction times.
Richard Platt  2017-08-08 06:24
Tidbits could usefully publish a piece about how to add a fusion drive to a desktop Mac. I'd like to, but don't know how, and it seems to be non-trivial.
B. Jefferson Le Blanc  2017-08-09 19:37
It is very non-trivial. Besides the fact that cracking open an iMac requires serious expertise, creating a fusion drive with an SSD and an HDD requires non-rtivial skills in Terminal. You can find out how to do it by doing a search on the Web—there have been article published on the subject. It's a topic for serious propeller-heads, which is to say, not me. ;-( It was easier in the old Mac Pros where the drive bays were easily accessible and no cracking was necessary.
Ned Mantei  2017-08-08 07:29
A bit off-topic here: I have a 2015 model iMac with a 1 TB SSD. "Find my mac"couldn't be activated, with the message that there is no recovery partition. In fact there is, but it's on a second SSD with 22.9 GB and which find my Mac doesn't see. I assume that all models, at least for 2015, got the 22.9 GB, with a rotating HD or an SSD forming in both cases a fusion disk. Possibly I could "unfused" the two, but so far have avoided looking into this. In any event, it seems that if you have any sort of fusion disk then find my Mac won't work.
Adam Engst  An apple icon for a TidBITS Staffer 2017-08-08 10:11
Curious. I would have expected Apple to make that seamless. It sounds like you have the 24 GB SSD portion of the 1 TB Fusion Drive. I'd think that the recovery partition would be on the hard disk portion, since it would be so infrequently used.

I don't think you can unfuse the drives in any useful way...
frederico  2017-08-09 01:26
You can add the Recovery Partition to the internal drive with third party utilities like Carbon Copy Cloner (free demo).
Ned Mantei  2017-08-09 06:23
Diskutil in the terminal says it's two separate physical drives.
Ned Mantei  2017-08-09 06:22
Carbon Copy Cloner says it won't do it, because it's a fusion drive.
B. Jefferson Le Blanc  2017-08-09 20:09
Are your two SSDs set up as a fusion drive? It doesn't seem so from what you say. In any case, you can't extrapolate about Fusion Drives given you rather unique configuration.

You should have a recovery partition on your 1TB SSD if it was original to the computer. Offloading it to another drive is an unusual arrangement to say the least. You may have to reinstall OS X in order to get the Recovery Partition where it should be. You could back up your system, them wipe the SSD and do a clean install. Then migrate the system from the backup. That's if Find My Mac is important enough to you to go to that much trouble.

I have a 2013 27" iMac with a 1TB Fusion Drive (with a 120GB SSD); Find My Mac works—at least I can turn it on in the iCloud preferences. I haven't actually tried to use it since I don't have an iPhone. But it is enabled.
David Redfearn  An apple icon for a TidBITS Supporter 2017-08-08 12:40
Talk about a disgrace: the standard horribly slow hard disk supplied with the base 21.5 iMac. My wife’s old iMac died and I made the mistake of buying the standard model because it was immediately available. My wife didn’t really notice any problem because she only uses the system for web browsing but every time I had to do maintenance work it drove me crazy. It’s very hard to replace the internal drive so I bought a Samsung external SSD, used SuperDuper! To image it, and now run off the external drive with _much_ improved performance. The internal drive now serves as a backup. I don’t understand why Apple does this - it can’t make a huge difference in their cost.

Philippe Lopatka  2017-08-09 05:07
Maybe they use slow HDs because of heating and reliability reasons? Those iMacs are so thin.. and so slow without the Fusion option!
Andrew James  2017-08-10 23:58
I too am disgusted that Apple cost-cuts on this essential component of computer performance to the extent that it undermines the whole experience. We are not talking about bargain basement hardware (price wise) yet Apple supplies 5400rpm drives, or provides a sliver of SSD for fusion.

Once a great advocate for Apple, my adour has decidedly cooled. I still appreciate their ecosystem as it works for me. However, I refuse to pay exhorbitant dollars for new hardware options that should be part of the default config. Instead I buy 2nd hand Macs that I can upgrade (e.g. 2012 models of Mac mini and MacBook Pro). And all these fly with SSD.

Unfortunately this strategy won't work long term so I live in hope that Apple will one day will provide desktop hardware that isn't fundamentally compromised at default configurations.
frederico  2017-08-11 17:33
Holy Cow!1 I just fired up one of two 2017 27" 5K iMacs BTO with 2TB Fusion drives; lo and behold, the SSD is NVMe, and the HDD is Seagate 64MB cache optimized RPM, running at 5900RPM normally, and revs to 7200RPM as needed.

Aja reports 2500+MB/s read(!!!) and ~760MB/s write with Fusion (presumably all on SSD as its only at 22GB used); 103MB/s read and 95MB/s write with HDD only.

In other words, the HDD is junk, and will eventually (for me, immediately) ruin the Fusion experience after it's full and starts relying on the HDD for video capture, scratch disks, Parallels/Windows, etc.

Lesson: absolutely do a 2TB or larger BTO Fusion drive, as the Fusion SSD slot still appears proprietary, and you will be extremely unlikely to find one used later. 32GB with the 1TB Fusion is pathetic, and only useful for the lightest of users.

I can't do it this minute, but I will alter my original plans a bit and split the Fusion for a KILLER independent NVMe SSD boot drive. (cont)
frederico  2017-08-11 17:39
(cont) I will hang an SSD RAID 0 on the back for data, and use the crappy internal OEM HDD for backups (probably clone, maybe Time Machine).

When the warranty is up, ill crack it open and throw in the fattest HDD I can find that gets at least 170MB/s+ r/w, such as an Iron Wolf Pro 128MB 7200RPM.

Happy Buying; welcome to an almost, could've been the best consumer mac ever.