Final Words

For the first time since late 2008, I went back to using a machine where a hard drive was a part of my primary storage - and I didn’t hate it. Apple’s Fusion Drive is probably the best hybrid SSD/HDD solution I’ve ever used, and it didn’t take rocket science to get here. All it took was combining a good SSD controller (Samsung’s PM830), with a large amount of NAND (128GB) and some very aggressive/intelligent software (Apple’s Core Storage LVM). Fusion Drive may not be fundamentally new, but it’s certainly the right way to do hybrid storage if you’re going to do it.

It seems that Fusion Drive is really made for the user who doesn't necessarily have a ton of applications/data, but does have a reasonable sized media collection. For that user, Fusion Drive should be a reasonable approximation of a well managed SSD/HDD setup with your big media files going to the HDD and everything that you launch frequently living on the SSD. I’m always going to ask for a larger cache, but I do believe that 128GB is a good size for most client workloads and usage models today. For me in particular I’d probably need a 256GB cache for Fusion Drive to win me over, but I understand that I’m not necessarily the target market here.

The real question is whether or not it’s worth it. I’m personally a much bigger fan of going all solid state and manually segmenting your large media files onto HDD arrays, but perhaps that’s me being set in my ways (or just me being right, not sure which one). Fusion Drive doesn’t do anything to mitigate the likelihood that a hard drive will likely fail sooner than a good SSD, whereas if you go with an internal SSD and external (Thunderbolt or USB 3.0) HDD RAID array you can control your destiny a bit better. Unfortunately, in situations where Fusion Drive is a choice, you don’t often have that flexibility.

On the iMac, Apple limits your options quite a bit. You can either buy a hard drive or the Fusion Drive on the 21.5-inch model, there’s no standalone SSD option. There the choice is a no-brainer. If you’re not going to buy your own SSD and replace the internal HDD with it (or try to see if OWC’s rMBP SSD fits), then the Fusion Drive is absolutely right choice. You’re paying handsomely for the right ($250 for 128GB of NAND is very 2011), but if you’re not willing to crack open the iMac case this is really the only way to go.

For the 27-inch iMac the decision is similarly difficult. Apple does offer a standalone SSD option, but it’s for a 768GB model that will set you back $1300. All of the sudden that $250 Fusion Drive upgrade sounds a lot more reasonable.

On the Mac mini side the decision is far simpler. The Fusion Drive is only available on the $799 configuration (for $250) but so is a 256GB SSD upgrade for $300. As long as you’re ok with using an external hard drive for mass storage, here I’d go for the big standalone SSD. The usual caveat applies: this  is only true if you’re not interested in cracking open the mini yourself and using a 3rd party SSD.

To make things simpler, I made bold the options I'd choose given Apple's current lineup in the table below. Note that this is still assuming you're not going down the DIY route (if you do go down that path, buy the biggest SSD you can find and rely on some external mass storage for everything else):

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

I am curious to see how long of a roadmap Fusion Drive has ahead of it. Will NAND get cheap/large enough that even the iMac can move to it exclusively? Or will we end up with systems that have more than enough NAND to easily store everything but large media files for even the most demanding of power users? In less than a year Apple could double the size of the NAND used in Fusion Drive at no real change to cost. I suspect another doubling beyond that would be necessary to really make Fusion Drive a one size fits all, but then we're talking ~2 years out at this point and I don't know how static everyone's usage models will remain over that period of time. Go out even further in time, to the post-NAND era and there are some really revolutionary things that can happen to the memory hierarchy altogether...

Fusion Drive Performance & Practical Limits


View All Comments

  • Andhaka - Monday, January 21, 2013 - link

    Nope, swapping the HDD with a SSD does not kill the warranty and many Apple users do that (I have done it on a 4 years old Macbook).
    But if other people find it better to pay for the Fusion solution (and a good solutions it seems to be) good for them.

  • pichemanu - Saturday, January 19, 2013 - link

    Hi Anand,

    i saw that in order to test a "pure ssd" setup you connected a 830 ssd to the imac over USB 3. As far as i know the best transfer rate over USB 3 is around 250 MB/s and the worst is well... terrible.

    Considering the best case scenario for the iMac:
    -USB 3 connected SSD would do 250 MB/s
    -SATA 3 connected SSD would do 322 MB/s (taken from your article)

    The performance would be 6.94 for fusion drive and 10.19 for a "pure SSD". This is an increase from 114% advantage for the "pure SSD" to 147% advantage for the "pure SSD".

    If on the other hand your USB connected SSD did not write at max and a SATA 3 connected SSD would (that is 350 for the samsung 830 on an intel Z77 SATA 3 port) that difference would skyrocket.

    Did you check that on your particular workload the USB 3 connection was not a bottleneck?

    Thank you.

  • mutatio - Saturday, January 19, 2013 - link

    Thanks, Anand, for the review. It would be interesting to see some comparisons to aftermarket Fusion setups as have been discussed in the comments here. e.g., How does the Fusion arrangement pan out with a 256GB or 512GB SSD on a Mac Mini? If my Mac were not a laptop I'd likely go for a Fusion setup but I'm not willing to take the hit in battery life while running an SSD and HDD (in the optical bay). Reply
  • philipma1957 - Sunday, January 20, 2013 - link

    I have a 2012 quad 2.3 mini using a 512gb ssd and the oem 1tb hdd. It works very well. I used to run this mini with 2x 512gb ssds in raid0. They were in a pegasus r6 case hooked up via t-bolt. I now run this with the 1.5 tb fusion and a tm plus a clone backup in the thunderbolt case. I prefer the setup this way. I have been doing this for a week I have about 480gb on the 1.5tb fusion . It will take me a while but I will put about 1tb on the fusion I will then see how much it slows. Reply
  • pichemanu - Saturday, January 19, 2013 - link

    A chart illustrating the possible impact of a USB 3 bottleneck on your test:

    Suddenly the fusion drive no longer looks that good ;).
  • mrbreaker101 - Saturday, January 19, 2013 - link

    I have a 2011 Macbook Pro with a 128GB Corsair Force 3 SSD and a 500GB hard disk. I decided to run the commands to make a fusion drive and so far, it's working, although the Force 3 isn't running that fast, despite being set to 6Gbps SATA.

    I'm going to install some new hardware in my iMac next. A 256GB Kingston Hyper X 3K SSD and 2TB hard disk (with thermal sensing cable from OWC, essential for iMac custom hard disk installs).

    I'm not entirely sure I want to make a Fusion drive on the iMac as well. My current usage is about 500GB, with most of that being music files. On one hand, I have no need for mp3s using up my precious SSD space, even if I listen to them 1000 times a day. On the other, the simplicity of no longer having to worry about the locations of files is very appealing.

    I also wonder, if I do a fresh install of Mountain Lion and then re-import my photos, media, etc, will Fusion Drive work better than by migrating over a Time Machine backup, which may fill the SSD with music, but leave apps on the hard disk?
  • ThomasA - Sunday, January 20, 2013 - link

    I have no experience with the 'fusion drive' but wonder about a clone/backup method, given the circumstances.

    I do have a MBPro with a 256GB SSD paired with a 'spinning' HD (replacing the DVD).

    I followed instructions offered by a Matt Gemmell, re: moving the 'home folder' to the HD. This allowed a backup clone of the SSD & a separate copy of the HD files.
  • twotwotwo - Sunday, January 20, 2013 - link

    Awesome that Anand can't resist throwing in some sort of enterprise-y benchmarks in a review of a consumer thing. :)

    I'm sort of curious how the enterprise caching solutions work on the real-world database-y workloads I've seen AnandTech do measurements of before. That's super workload- and software-dependent (how big is your working set? how fat is your long tail of requests outside it?) so AT's results wouldn't directly apply to the world at large--still, one data point is a big step ahead of zero. :)

    (It also seems to be increasingly a thing to design enterprise stuff with data 'intelligently' routed by to SSD or HDD by application-aware software [Evernote has done this, say, and Amazon offers SSDs and HDDs in separate instance types], rather than routing with magic at the block device layer. Still, would be awesome to know anything at all about how effective the automagical caching is in databases.)

    And, unrelatedly, I'm sure Apple will get rid of the Pros with HDDs when they can, and I hope most other manufacturers do, too. You don't need TBs of internal storage now (esp. if videos are streamed, cloud storage an cheap externals exist, etc.) and Flash is good for speed, size and weight, durability (no head crashes!), etc.
  • carraj - Saturday, January 26, 2013 - link

    Machine: 2010 15" MacBook Pro, 8 GB RAM. Disk controller is SATA II, so pointless using SATA III devices.

    Installed 750 GB WD Scorpio Black HDD in optical drive bay using Data Doubler bracket (/dev/disk1).

    Installed 240 GB OCZ Vertex Plus R2 SSD in HDD bay (/dev/disk0).

    Both were formatted as JHFS+ using Disk Utility. A Recovery HD partition was created on the HDD using Carbon Copy Cloner as /dev/diak1s3.

    Fused /dev/disk0s2 and /dev/disk1s2 together giving ~1 TB Fusion Drive.

    Performance is incredible, though not quite as fast as my mid-2012 13" MacBook Air with 256 GB SATA III SSD in tests. Here are the results from Xbench 1.3 (the Fusion Drive clocks in at about 2/3 of the performance of the pure SSD, despite having a 3 Gb/s SATA II interface rather than a 6 Gb/s SATA III interface):

    15" MBP with 240/750 GB SATA II Fusion Drive:

    Disk Test 277.85
    Sequential 180.25
    Uncached Write 412.52 253.28 MB/sec [4K blocks]
    Uncached Write 278.11 157.36 MB/sec [256K blocks]
    Uncached Read 89.26 26.12 MB/sec [4K blocks]
    Uncached Read 201.26 101.15 MB/sec [256K blocks]
    Random 606.00
    Uncached Write 555.66 58.82 MB/sec [4K blocks]
    Uncached Write 531.52 170.16 MB/sec [256K blocks]
    Uncached Read 1566.27 11.10 MB/sec [4K blocks]
    Uncached Read 438.38 81.34 MB/sec [256K blocks]

    13" MBA with 256 GB SATA III SSD:

    Disk Test 431.86
    Sequential 278.39
    Uncached Write 720.45 442.35 MB/sec [4K blocks]
    Uncached Write 479.45 271.27 MB/sec [256K blocks]
    Uncached Read 106.55 31.18 MB/sec [4K blocks]
    Uncached Read 662.54 332.99 MB/sec [256K blocks]
    Random 962.48
    Uncached Write 751.67 79.57 MB/sec [4K blocks]
    Uncached Write 748.11 239.50 MB/sec [256K blocks]
    Uncached Read 2147.57 15.22 MB/sec [4K blocks]
    Uncached Read 977.31 181.35 MB/sec [256K blocks]
  • kamaaina - Tuesday, February 12, 2013 - link

    I am very happy after 6 weeks with my DIY Fusion Drive in my MBP. Replaced the optical drive as well and moved the HDD 500GB Momentus XT into the DVD HDD tray, and put an Intel330 240GB SSD in. Fused together, it runs really well. I followed the video on Youtube from Tomas Villegas, took me a only a few minutes. Awesome improvement! Reply

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