Fusion Drive v. SSD Performance Difference in all-new 27 inch iMac

Discussion in 'iMac' started by JakeE, Dec 18, 2012.

  1. JakeE macrumors newbie

    Nov 7, 2004
    Why would anybody purchase the 756 SSD option in the all-new 27inch iMac and pay $900 more than a 3TB Fusion Drive? If the two perform the same or similarly, why would anybody pay $900 more, and gets less than 66% of the capacity?

    I ask this because I want to get a new 27 iMac, and I am mostly concerned with overall speed performance, and I am trying to figure out if you have a maxed-out all-new late 2012 27inch iMac with a 3TB Fusion drive, compared to the exact same machine with a 756SSD, would there be any performance difference.

    Any thoughts or ideas?
  2. flynz4 macrumors 68040

    Aug 9, 2009
    Portland, OR
    It completely depends upon your data. If your "hot data" (data that is accessed very often) is greater than 128GB... then of course performance will matter. I think for "most" consumers... fusion offers a good compromise of "near SSD" level performance with HDD capacity.

    Personally... I am leaning toward the 768GB SSD. I suspect that I am in the 10% who would notice the difference.

  3. snugja macrumors regular

    Feb 11, 2006
    I'm an Industrial Designer. I opted for the Flash SSD mostly because of my experience with the macbook air. I love how cool it runs and fast the SSD makes the machine feel, despite it having only 4gb ram and a 1.7Ghz Core i& processor.

    I do a lot of CAD, Processor and machine intensive rendering, as well as working with BIG files, so having fast performance throughout the entire storage block is important to me. My wife, a graphic designer, frequently works with multiple 1GB or larger files. Again, the same speed factor is important.

    The concept of the fusion drive is that the SSD portion of the drive witll keep your most used files, programs etc, thus giving the feeling that the system is zippy. Once you've maxed out that 128GB storage block, everything else would be accessed at regular 7200 Rpm harddrive speeds. I'm sure for most this won't be an issue or noticeable, but to each their own.

    So the SSD is pricey, but worth it to some. I think it just depends on how you're going to be using space etc.

    The 3TB fusion drive is also not supported by Bootcamp at this time, if that's something you do. I actually had the 3TB on order, then changed to the SSD later on for that reason. I need Bootcamp (not parallels) to run a few programs at full speed.
  4. chorner macrumors member

    Aug 4, 2012
    Toronto, Canada
    I also back the purchase of the 768GB SSD option for my usage, as well as keeping my systems completely free of mechanical drives from now on. Any larger storage requirements are dumped on an external.

    I prefer the piece of mind when it comes to reliability (especially in a sealed-up computer), speed, noise, and heat reduction that you find with just an SSD installed.

    More expensive, but worth it. I went with the 768GB SSD option on my MacBook Pro Retina - though I'd do the exact same for the iMac purchase.
  5. JakeE thread starter macrumors newbie

    Nov 7, 2004
    Thanks for the great answers...

    After I posted, I realized I should be more specific.

    I was 16 years old in 1984, and I cut sixth period of class in my high-school to go and pickup my first Mac on January 24, 1984. I brought it home and was amazed at how cool it was, but it seemed like it took forever to do most things.

    My eternal dream has been to one day get a computer that could actually keep up with me–where I didn't have to wait for the computer to compute. Decade after decade, and year after year computers have gotten faster, but always too slow, but with my current computer that all changed–kind of…

    My current Mac is a Quad Core Intel i7 3.4 GHz with 16GB of RAM and the 2GB AMD Radeon video card. I love this thing and it comes so close to being perfect with speed. Instead of waiting 30 seconds for Photoshop or Illustrator to load…BOOM!!! It takes a second or two. Same thing with almost everything. I feel like speed wise this thing is 97% as fast as I would like, which is great, but I also feel like if it had 32GB or 64GB of RAM is would fly much faster.

    I am excited to get the all-new 27 inch with 32GB of RAM, and I think USB 3.0 will make a huge difference. The lighter weight, better screen are icing on the cake.

    I swore I would never buy anything with a spinning hard drive ever again, and that it was only SSD from now on. That being said, I can't seem to stop thinking about how much I would like the extra 2.875GB of extra Space, and the $900 price difference is almost $1000 in price difference savings with Tax.

    Basically, I want a computer where everything is instantaneous, and I can't help but wonder how different if at all the SSD would be from the 3TB Fusion Drive?

    I know this might sound crazy, but one of my pet peeves with my current computer is that I have my large music collection on an external drive, and often times when I press play in iTunes after no song has played for a while, it takes 10 seconds to spin up the external HD, which drives me crazy. I want the music to start instantly, and I know with the SSD this will be the case, but what if I have a Fusion drive? Will is also start playing the music instantly or will I have to wait for it to start if the music is not located on the SSD portion of the fusion drive?

    Also, I am wondering if the overall speed of the 768 SSD is faster than the 128 SSD in the Fusion drive? The current SSD in my iMac has the lame 3 Gigabits per second read speed, but I think I read the Retina Macbook and all-new iMacs have the faster 6 Gigabits per second read speed. But what about the SSD in the Fusion Drive? Is it the 3G or 6G? If it is 6G for most things it seem like you would not see much if any performance difference?

    Any other insight or opinions?
  6. flynz4, Dec 18, 2012
    Last edited: Dec 18, 2012

    flynz4 macrumors 68040

    Aug 9, 2009
    Portland, OR
    Probably not significant.

    One of the most confused aspects of HDDs is data rate. In the vast majority of cases... it is not that important. What matters MUCH more is IO Operations per second (IOPS). IOPS is what makes everything seem fast. By contrast, MB/s measures bandwidth... and like HDDs... that bandwidth is measured over larger transfers of data. Client computers predominantly have much higher access to small blocks of random data. This is not well measured by MB/s testing.

    I read an article recently where they compared this to two different cars. I'll make up new numbers since I cannot remember the exact example.

    Car A: 0-60 in 5 seconds... top speed of 150
    Car B: 0-60 in 20 seconds... top speed of 200

    Which car is faster? Car A would feel like a jack-rabbit... give you spectacular passing peformance... etc.

    Car B would eventually go faster... but would feel like a dog. You push the gas peddle and wait.

    Neither Car A or Car B would ever use its top speed in normal driving situation... so Car A would clearly be the performance vehicle.

    In storage... IOPs is like instantaneous performance (0-60 in 5 seconds). By contrast, MB/s is the top speed (200 MPH)... which in most cases... is not a very important figure.

    MB/s is a remnant of testing HDDs. It is not very applicable to SSDs in my opinion. It is easy to measure MB/s. You move a ton of data and time how long it takes. Measuring IOPS is still immature, and easy to "rig". This needs to get fixed before we can easily measure SSD performance.

    Rest assured... SSDs greatly affect the way a computer "feels". The more you have... the better the machine will perform in most situations.

    However... if your hot data really can fit on the SSD portion of the fusion drive... and if Apple's fusion software is good... then the difference between fusion and full SSD will be small.

    OTOH... if your hot data largely spills over onto the HDD... then fusion will not perform the same as a full SSD.

    You need to know your data usage to know if fusion or full-SSD is the best solution for your situation.


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