Meet Fusion Drive

Available as a build-to-order option on both the new Mac mini and the new iMac is Apple’s own take on SSD caching, Fusion Drive. In true Apple fashion there are only two Fusion Drive configurations available: 1TB and 3TB. The 1TB option is only available on the upgraded Mac mini ($799) or any of the iMacs, while the 3TB Fusion Drive is a 27-inch iMac exclusive.

In all of these cases, the Fusion Drive is a combination of a 1TB or 3TB hard drive (2.5” or 3.5”) and a 128GB Samsung PM830 based SSD. In the Mac minis this SSD is a 2.5” drive, while in the iMacs it’s the same custom interface that’s used in the MacBook Air and MacBook Pro with Retina Display. For my testing I used a 1TB Fusion Drive in a 27-inch iMac.

Fusion Drive Options
  Mac mini (2012) Mac mini (2012) Mac mini server (2012) 21.5-inch iMac (2012) 27-inch iMac (2012)
Base System Cost $599 $799 $999 $1299/$1499 $1799/$1999
1TB Fusion Drive - +$250 - +$250 +$250
3TB Fusion Drive - - - - +$400
Largest Standalone SSD - 256GB
- 768GB

The size of the SSD used in Apple’s Fusion Drive is much larger than what we usually find in a caching setup. Most OEMs ship with 8 - 24GB of NAND, and even then the drives rarely use a good controller. In the case of Apple’s Fusion Drive, Samsung’s PM830 continues to be one of the best combinations of performance and reliability we’ve ever tested. While I would’ve personally picked something like the Link A Media or Intel S3700 controller due to their excellent performance consistency, the PM830 is probably a more proven and/or affordable option for Apple.

Right off the bat Fusion Drive is different than most of the hybrid/caching solutions we’ve seen, but where it really diverges from the norm is in the software component. This isn’t simply Intel’s Smart Response Technology running under an Apple brand, instead we’re looking at virtualized storage courtesy of OS X’s Core Storage. First introduced in Lion, Core Storage is a logical volume manager that allows the OS to treat multiple physical disks as a single volume.

Apple originally used Core Storage to enable full disk encryption in Lion, but its use has been expanded to Fusion Drive in Mountain Lion. The creation of a Fusion Drive is simple. If you have multiple drives you can create a Fusion Drive yourself using some simple Terminal commands. When you buy a Fusion Drive equipped Mac, Apple does everything for you. Subsequent system and backup restores on your Mac with FD will maintain the Fusion Drive facade, even if you’ve purposefully destroyed the array.

Unlike traditional SSD caching architectures, Fusion Drive isn’t actually a cache. Instead, Fusion Drive will move data between the SSD and HDD (and vice versa) depending on access frequency and free space on the drives. The capacity of a single Fusion Drive is actually the sum of its parts. A 1TB Fusion Drive is actually 1TB + 128GB (or 3TB + 128GB for a 3TB FD).

The latest version of Disk Utility will present a Fusion Drive as a single drive, labeled Macintosh HD from the factory. Apple doesn’t attempt to hide the FD underpinnings however, looking at System Report or using a third party utility like iStat Menus you’ll get statistics on both drives:

If you’ll notice, the 128GB SSD is reported as having a 121.33GB capacity. Since OS X 10.6, Apple has reported capacities in base 10 but if you do the math based on the capacity in bytes you’ll get an idea of how much space is set aside as spare area:

Apple Fusion Drive, SSD Spare Area
  Total NAND Exposed Capacity Spare Area
Apple Fusion Drive 128GB SSD 128 GiB 113 GiB 15 GiB

Approximately 11.7% of the 128GiB of NAND is set aside as spare area, which is no different than what you get with a 128GiB SSD in a standard Mac, but a bit higher than the usual 6.7% spare area you get with most of these drives. The added spare area will help improve performance consistency, but it’s still a bit shy of what I like to see on Samsung SSDs (~25%).

You can create Boot Camp or other additional partitions on a Fusion Drive, however these partitions will reside on the HDD portion exclusively.

Introduction Fusion Drive: Under the Hood


View All Comments

  • StormyParis - Friday, January 18, 2013 - link

    The device is technically nice, however the price is wayyy too expensiveat around $450 for 128GB+2TB:

    Apple's 128GB SSD+ 2TB HDD "Fusions drive" is about $450 ($400 as an upgrade)

    A regular 256 GB SSD is $170
    A regular 3TB HD is $150.
    regular equivalent for Apple's price: 256 SSD+ 2x3TB HDD = $470

    You can get twice the SSD storage, and 3 times the HDD storage, for about the Apple price. This will take up more physical space, but also offer you way more storage space, both on the SSD side (plenty of space for your OS, apps, and live data files) and HDD space (3TB + 3TB backup, or 6TB JBOD for your archives and media)
  • jeffkibuule - Friday, January 18, 2013 - link

    Hence the DIY route. Reply
  • Galatian - Friday, January 18, 2013 - link

    Thanks for pointing this out! I was very interested in getting a new iMac, as I love working on my 13" rMBP, but since I still like to game I really wanted to use the SSD on bootcamp as well. It is a huge step backward for all those people who want/need bigger SSDs. The only other option Apple offers is the 768 GB version for a whopping 1300€ upgrade price. There is no other size in between. Apple has lost me on that one. Reply
  • BrooksT - Friday, January 18, 2013 - link

    So Apple is charging $150 to take away the headache of managing files. What you call "gouging" is what many people call "charging for a service." Reply
  • Death666Angel - Friday, January 18, 2013 - link

    Again I have to wonder what you do with your PC. It appears as though you have no idea what is on your PC, because even saving a .doc in a specific folder is "managing files". Do you just save everything to desktop? Or download everything from the cloud and then start it from the browser download window? Reply
  • name99 - Friday, January 18, 2013 - link

    And I wonder if you have EVER actually
    (a) viewed how NORMAL people use computers,
    (b) used a Mac more recently than ten years ago.

    Apple realized a long time ago that people has MASSIVE difficulty dealing with the file system and naming/finding files. Practically every large advance in Apple tech has been to deal with this.

    iTunes and iPhoto are about dealing with "songs" and "photos", not "song files" and "photo files". Both create an environment where you never have to give a damn about where your songs and photos are stored or named in the file system. iPod follows the same path, and iOS is the logical endpoint, with no user visible file system.
    And this is not new --- did you EVER expect that you should have to manually organized your email files into folders?

    In OSX Apple first tried to simplify things with automatically provided folders for the most common situations (Documents, Downloads, Music, Movies, Pictures).
    Now, in Mountain Lion Apple is, through a combination of different features (version storage, automatically opening apps at reboot, auto-storing files in iCloud) trying to make it so that, more and more you don't have to name documents created in apps like TextEdit. You CAN, but you don't HAVE TO.

    Insisting on manually controlling the placement of your files really does start to come across as no different from insisting on writing assembly code.

    Look, I'm not an idiot. I have multiple external hard drives connected to my multiple machines, and I have a purpose for the different hard drives.
    The difference between you and me is that I'm not so deluded as to imagine that my needs are in any way typical, and that everyone else would be better off being forced to do things like me.
  • Death666Angel - Friday, January 18, 2013 - link

    I see how other people use PCs. They are managing their stuff, even if they just put documents in a document folder, photos in a photo folder etc. I don't even know what not managing files would look like. Hence why I asked.
    I don't use Apple products.
    I manually organize my Emails to folders in Thunderbird.
    I also don't use the Windows libraries or the media player library or any of that stuff. I have no found a program that gave me the ability to organize "non-files" (songs, photos etc.) in a way I found easy to use, well arranged etc. I also like my files to be program/OS independent.
    I don't think I'm the typical user. I never said as much.

    Your last point though tells me that you don't understand the meaning of my post here. Read the other post that I did not replying to anyone. That should make it clear that I am against this technology. But if someone says he is not managing files, that just sounds dumb (real world equivalent: I don't clean up my closet and have no idea where what is).
  • KoolAidMan1 - Friday, January 18, 2013 - link

    So many spergs in tech forums, it is unbelievable.

    I'm certain that most of you have low level autism and have no idea how people in the real world are.
  • Death666Angel - Friday, January 18, 2013 - link

    I' pretty sure I'm not. What I am sure of, though, is that you are a dick. :P Reply
  • kyuu - Saturday, January 19, 2013 - link

    People who do the simplest management of their files (saving photos to a Photos folder, music to a Music folder, etc.) have "low-level autism"?

    The argument that basic file management is hard or a "headache" is absurd. It takes no time at all, and managing files and apps between an SSD and an HDD is no more difficult or time consuming than that.

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