Details emerge on Apple's Fusion Drive technology

Details emerge on Apple's Fusion Drive technology

Summary: Apple posts a support note about the Fusion Drive offered for its new iMac and Mac mini models. The result is some interesting answers and even more questions.


At last week's event introducing the iPad mini, Apple also rolled out new iMac and Mac mini models that can be configured with a proprietary "Fusion Drive." This technology presents a solid-state drive (SSD) and a hard disk drive (HDD) as a single volume to the user. There are all kinds of labels being applied to the technology, however, it looks to me that Fusion Drive employs a kind of hierarchical storage management (HSM) that tracks file and application usage and migrates frequently-used items to the quicker SSD.

As a result you'll enjoy shorter startup times, and as the system learns how you work you'll see faster application launches and quicker file access. Fusion Drive manages all this automatically in the background.

In Apple's About Fusion Drive technical note, it's clear that this capability isn't a function of the drives themselves, rather it's based on Apple's storage management software. Fusion Drive is a built-to-order selection in the Apple Store.

According to the note, Fusion Disk systems come with a "special version" of Disk Utility. It warns that earlier versions of Disk Utility can't be used with a Fusion Drive. We don't know whether there is a unique version that ships with the Fusion system, or whether everyone receives the same software and the "special" Fusion capabilities are revealed in the presence of a Fusion setup. But it's the same difference.

The note also warns that current versions of third-party disk utilities may or may not be compatible with the Fusion Drive. This would include various file and volume monitoring tasks often controlled with preference panes. Time Machine deals with the Fusion Disk as a single volume.

In addition, there are limitations with Fusion Drive and Target Disk Mode. To mount the Fusion Drive, the host system must be running Mountain Lion version 10.8.2 or later. Earlier versions of Mac OS X can't mount a Fusion Drive in Target Disk Mode.

There may be issues with the sustained data capture rates with Fusion Drive. Here's an item from the FAQ:

I'm using video capture software and it reports frame drops during sustained captures. What could be wrong?

Your project's capture requirements may exceed the sustained capture rate available to your Fusion Drive. Try capturing a smaller segment of the source or reduce its resolution.

In an interesting Betalogue blog post, Canadian IT consultant and author Pierre Igot pointed to another item in the tech note, where Apple offers a series of steps to take if the Fusion Drive system doesn't start up and you see the flashing question mark or another alert. But as we read, the end result isn't reassuring or entirely satisfying:

To repair the volume, click Fix. CAUTION: Clicking Fix will erase your Fusion Drive.

Igot suggests that the flashing question mark is rare occurrence nowadays, but a sign of serious disk damage. He worries "that the flashing question mark problem might occur more frequently with the Fusion Drive than with current drives, but that it’s not indicative of a hardware failure and can actually be fixed."

Maybe I’m reading too much into this. Maybe Apple is just being cautious and making sure that the required information is available in the rare cases when such a failure might occur. On the other hand, Apple is a company that tends to remain in denial about problems until reports reach some kind of internal critical mass. So this particular tech note looks rather unusual to me. After all, nobody except Apple people with access to prototypes is using a Fusion Drive right now.

It's too soon to understand the Fusion Drive's advantages and potential issues in professional workflows. Mac managers should proceed with caution until more is known.

If you want the speed advantages of running both a SSD and HDD, but without the automatic performance management, check out upgrade kits from vendors such as Other World Computing's Data Doubler series. One works with the new Mac mini 2012.

Topics: Apple, Laptops, Operating Systems, Servers, Storage

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  • Questionable Advancement

    It is very interesting and troubling to see that some usage scenarios seem not to be suitable for the Fusion drives.

    As far as we know today, it really looks to be some logic that transports files from the HD to the SSD based on some usage heuristics. Does this gimmick really worth the premium price?

    What else does it hides?
    • Back in the System 7 era there was a great utility that did this, too.

      Disk Express II was a disk defragmenter and optimizer. It defragmented all files, but would place the OS and frequently accessed files on the innermost tracks of the platter and less used files in the outside platters keeping free space a single contiguous block between the two. I remember it speeding data capture rates on my AV machine substantially.
      • That's something I don't remember hearing about, Matthew

        My biggest memory of those days is RamDoubler, a very handy utility. Another memory is that I never had a SCSI HD go down on me. Not that I can complain; so far I've only had one HD go down anyway. I lost nothing except a bit of time.
        Laraine Anne Barker
      • OS X defrags automatically

        OS X defrags and optimizes in a similar fashion with each installation.
  • You've been able to get this on the Dell XPS One for quite some time

    It's called Intel Rapid Storage Technology.
    • Unwanted Clarifications

      Thank you for this amplification on a point no one made. Plus, since "Intel" is in the name, I expect it's more an Intel feature than Dell. I'd investigate if I cared.

      I appreciate that we all need quests; one of yours is apparently making sure that Apple is never credited with being first, even when no one is talking about who was first. Apple was or wasn't first? So? I don't think that this technology, assuming it's of use to me, is the dealbreaker as to whose computer/os/applications I use.

      However, if I was a video production house using Apple servers for primary capture, the note about latency that Mr. Morgenstern provides would be very important to note before making the capital purchase.

      I also take it that the warning about outside disk repair tools suggests that despite this having been available via Dell for the tech-equivalent of ages, the ISVs haven't written a fail-safe repair utility, therefore what Apple is doing must be a little different.

      But, thank you again. Hey everyone, Dell had something like this already and based on sales results, you didn't care then and you don't care now. Noted.
      • Sadly your reply is typical of ZDNET


        Considering in the first paragraph the technology is described as "..proprietary Fusion Drive" one could be forgiven for thinking this was a completely new invention based on a completely new idea.

        Not sure what your quest is, but I'm sure if you took time out from your sad little life, invented something that no one cared about, and then suddenly 10 years later someone "re-invented it", you'd surely want credit.

        I know I would. But hey, that's just me.
        • Sadly typical of bloggers

          I wondered if this was just one of the existing combined drives you can get.

          The point of the article is that this is actually some Apple tech and is proprietary and not one of the already available drives.

          Could one forgive you for making the word Proprietary mean something it doesn't then whining about it?
      • More Apple Marketing

        If its of no benefit to you, move on. There are many posts in these threads that have no value or information, this is not one of them at least.. because he has a valid point.
    • No it isn't...'s OSX which decides what should be where and is more akin to tiered storage LVM than a flash disk cache. This means Apple (& perhaps us) get to decide the performance enhancement rules rather than the one-dimensional significance=frequency of access that hybrid drives & Intel SRT employ.

      It also means we may be blessed with the ability to fuse other drives not just for performance enhancement but for simple storage scalability i.e. MacBook Air SSD + Timecapsule HDD rendering the old buy-the-biggest-HDD-you-can-because-after-market-upgrading-&-management-is-just-too-hard philosophy redundant. Maybe enterprising 3rd parties can leverage OSX's CoreStorage framework to save time waiting for Apple.

      For me, Apple missed a golden opportunity with this. They should have made the new iMacs paper-thin & SSD only with an external (cable or WLAN) Fusion Drive option. Pros use external arrays anyway, most consumers never fill a 128GB drive and an overspill option should serve the rest well.
      It'll be interesting to see how Fusion Drive splits Aperture/iPhoto libraries.
      • All Good Points

        @McDaveH: I completely agree with your points. Couldn't have said it better!
    • Apparently not caching

      "In a caching solution, like Intel's, files live on the hard disk drive and are temporarily mirrored to the SSD cache as needed. In an enterprise auto-tiering situation, and with Fusion Drive, the data is actually moved from one tier to another, rather than only being temporarily cached there."

      Personally, I'd rather have a straight SSD internal drive and a Raid10 external drive on Thunderbolt.
      George Marengo
  • Sounds like Dataplex

    Crucial (and Corsair, apparently) make SSD cache drives ( that use a piece of software called Dataplex. The software scares the heck out of me for a lot of the same reasons that this article alludes to - Dataplex sits at an extremely low level of the system, has no user interface, hides the SSD drive from Device Manager, and data recovery can get particularly interesting if you actually need to run a utility for the task. However, it is indeed an extremely fast and inexpensive solution for PC users to do the same thing.

  • These have been around since 2007

    Apple is a "mature" company now and we'll see more "Like the old one, but now with more Apple!!" spin like the other "mature" companies...
    • Way to pay attention...

      The Fusion Drive is not merely a hybrid SSD/spinning platter drive. In fact, Alan Malventano of PC Perspective has frequently trashed those solutions as a real disappointment in having any meaningful speed increase at all.

      Fusion Drive may or may not be anything Apple proprietary, but it most definitely is not a simple hybrid SSD.
  • Gee Whiz!

    Does anyone find it annoying when, amongst intelligent posts, some human species decides to butt in with ignorant comments which are totally irrelevant to the point being addressed. For goodness sake and for intelligence's sake, get a life! If you hate anything Apple, whether Dell had the technology first, or this was invented in the stone age, don't comment! You are a lost cause, go and argue whether Santa Claus exists or not. IMO ZDNET should ban Trolls and people who just want to make it a point of being haters. Someone should conduct a survey as to the ratio of Apple Vs PC or Android people who just love to rubbish whatever technology is discussed in the articles. If you want to take me on personally, I for one am a Mac user who deals with Windows users in a mixed environment and happy to help them all with their frustrations. No OS is greater, they all have their place and people either enjoy using one or the other. Technology when named differently and whether it's been there before or not may be different, we don't know. If you have a factual comment to make then do as I teach my students - Back up your opinions with references. No references = Epic fail.