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
(+$300)
2x256GB
(+$600)
- 768GB
(+$1300)

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
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  • 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.
    Reply
  • 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).
    Reply
  • 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.
    Reply
  • 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.
    Reply
  • KoolAidMan1 - Saturday, January 19, 2013 - link

    Nope. See this is what I'm talking about.

    It isn't about lack of technical knowledge, it is about lack of EMPATHY.

    Just because you or I or anyone around here can manually manage things doesn't mean that we should bash on automated solutions for normals. I used to write custom config.sys and batch files to get my DOS games to run properly 20 years ago, but I did it because I wanted to play the game, not because I enjoyed jumping through technical hoops.

    I'm sure if you told some nerd back in 1993 that maintenance of their games from both the download service and the operating system would be the norm in 20 years, they'd bash on it for not being "hardcore" enough.

    Jumping through technical hoops is nothing, you're right, its easy. It also isn't something to hold over the heads of people who don't want to go through that work.

    Again, empathy, something so many insecure tech geeks are lacking when it comes to thinking about technology and products.
    Reply
  • Galatian - Sunday, January 20, 2013 - link

    Apple isn't gauging 150$. They are charging you 250€ for a 128 GB SSD! 250€ = 333$ at the current rate. Not to mention the fact, they simply don't have anything in between. It's either 128GB SSD or 766GB.
    I'm not sure why everybody is so apologetic about Apple on this one. They gave you much better option on last years models. They actually took options away. While I could deal with a lot of the "anti-consumer" moves that Apple has made late, this is just over the top. The new iMac is nothing more but a bigger Notebook and hence has completely lost it's value as a desktop machine.

    Oh and please: How hard is it to manage files? 256 GB is fine for all my files (programs + games). Games I don't play I simply deinstall from Steam. I have a VDSL 50.000 line here, so redownloading them is a no brainer. Same goes for other programs. It must be an American problem with slow inter connections...

    Also the way iPhoto handles files is extremely awkward: It actually creates a second copy of the file in another folder. That might me elegant on the surface, but I see absolutely no advantage over simply having a nice hierarchal folder structure. In fact that's what iTunes superbly does. It is a big bag of hurt, that Apple is inconsistent with the way they manage files!
    Reply
  • edlee - Friday, January 18, 2013 - link

    I get the cached solution for fusion. But I would rather just handle the usage myself and have os and applications on SSD and all media on a Raid array.

    SSD for life.
    Reply

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