question on ssd vs fusion

Discussion in 'iMac' started by foster26, Dec 11, 2014.

  1. foster26 macrumors member

    Sep 22, 2014
    I am going to be buying a new 5k and having a hard time deciding on getting a ssd or the fusion drive. My question is how much more performance will i get if I get it with the ssd. I would want the 512gb at least. Thanks
  2. yjchua95 macrumors 604

    Apr 23, 2011
    GVA, KUL, MEL (current), ZQN
    Fusion read/write: 700/350 MB/s.

    Pure SSD read/write (512GB): 730/720 MB/s.

    I would go for the SSD-only setup for pure speed and reliability.
  3. foster26 thread starter macrumors member

    Sep 22, 2014
    Thanks. Doesn't seem like a huge difference, but it might be. It's amazing the price difference on the 2 and was thinking it would be great to have the extra space with the fusion but want the best speed I can get. Anyone get the fusion and wish they got the ssd, or vice versa? Thanks
  4. chabig macrumors 601

    Sep 6, 2002
    I think that in real use, you will never notice a difference between the two.
  5. maflynn Moderator


    Staff Member

    May 3, 2009
    I could be wrong, but i think the differences grow as your fusion drive fills up and more and more of your data sits on the hard drive as opposed to the SSD.

    I think Apple's implementation of this is great but I think over time, the speed of the SSD will remain constant, where as the fusion drive will slow down as it will access data on the HD. I think thanks to caching it may get mitigated to some degree but not completely.
  6. JustMartin macrumors 6502a

    Feb 28, 2012
    It really depends on your usage profile. If you regularly access more than 128gb of different disk blocks or write more than 4gb in one go, then you might want to consider pure SSD for speed.

    If you have more than 512gb of files and you don't want to have additional drives (apart from backup), then you might want to consider fusion for the additional storage.

    Personally, my fusion drive suits me. The files I work on are relatively small and I tend to work on them for days at a time. This means, most of my stuff goes on the SSD part of the fusion drive. But, I don't deal with large amounts of graphic data that might overflow the SSD and start hitting the hard disk. And I'm older so the difference of a second or two in response time doesn't feel like it's murder :)
  7. Fafa2e macrumors newbie

    Dec 9, 2014
    I had a similar dilemma and went with the 512 GB SSD. I will primarily use the computer for HD video editing with motion graphics (including some 3D through mObject). I plan to store the video files on a separate external hard drive connected with Thunderbolt 2 and to move any events that I am currently working on to the internal SSD for faster video performance. (I just bought the Lacie d2 Thunderbolt 2 3TB, although I know that the Thunderbolt 2 is overkill as the 7200 RPM drive can't even reach Thunderbolt 1 transfer rates.)

    I have not yet received my machine, but I believe that this should give me the fastest workflow.

    (Note: I am a hobbyist, so I don't have any deadlines, but I still wanted a fast workflow.)
  8. joema2 macrumors 65816


    Sep 3, 2013
    I have stated that myself, however the reality is more complex. A regular HDD will definitely slow down as it fills up, hence the common recommendations to have at least 20% free space. In some performance-intensive applications people recommend 50% free space.

    However a Fusion Drive is not like that. I recently ran performance tests on my 3TB Fusion Drive at 93% free space, then at 1% free space. Using the largest tests of both BlackMagic and QuickBench, the 3TB FD was 90% as fast at 1% free space as at 93% free space. IOW there was little performance degradation as it filled up -- using those particular I/O profiles.

    However if copying bulk data (not typical application I/O), a nearly full FD will degrade a lot more than an SSD as they both fill up to equal percentages.

    While there's a significant difference in *benchmark* write performance between SSD and FD, I think most people in real-world usage will not notice a dramatic performance. The FD does give a lot more free space and could avoid having to immediately purchase a (likely slower) external HDD.

    That said if you're buying a fast external HDD anyway, why not get SSD. It will be faster in some conditions than FD.
  9. boast macrumors 65816


    Nov 12, 2007
    Phoenix, USA
    So in FD, the ssd acts as a cache drive. If the cache drive fills up, then it will need to keep swapping things from the hdd to the sdd based on usage and profiling. If it is on the ssd it will have ssd speed reads, if it was not, it will have slow hdd reads.

    How did you get blackmagic to decide to test from it being cached on the ssd or on the hdd?
  10. foster26 thread starter macrumors member

    Sep 22, 2014
    I do have a nas drive with a ton of extra space so that should be a problem. I think I will get the 512gb ssd and store all apps on there and store the photos and videos on the nas.
  11. RUQRU macrumors regular


    Apr 14, 2011
    Mac Addict!
    SSD wins everytime. Future proof your purchase. Use external Thunderbolt drive for storage.
  12. joema2 macrumors 65816


    Sep 3, 2013
    All caches are much smaller than the backing store, whether a disk cache, CPU instruction cache, data cache, etc. Caches don't "fill up" then become unusable, rather less important items are bumped from the cache to make room for more important items.

    You don't have direct control of this. I used DiskTester's "fill volume" command to fill the FD 99% full, then used BlackMagic's largest test size (5 gigabytes). If it's cached by SSD -- good, if not -- too bad. In this case it was cached by SSD, despite the Fusion Drive being 99% full.
  13. mlody macrumors 6502a

    Nov 11, 2012
    Windy City
    if you are thinking about running any VMs, the SSD is the way to go.
  14. joema2 macrumors 65816


    Sep 3, 2013
    If that works for you, good. Just keep in mind transfer speed from a NAS is typically much slower than a direct attached hard drive.
  15. forg0t macrumors member

    Aug 13, 2014

    The fusion drivers will only be at that speeds for the first 128gb or so, then they will drop in performance the fuller it gets.

    I opted for the 256GB, but I found myself looking for an external HD weeks later. I don't regret choosing SSD, but do wish I went with the 512GB since the upgrade alone costs about the same as an external thunderbolt raid drive.
  16. joema2 macrumors 65816


    Sep 3, 2013
    As I explained above, Fusion Drive does not generally drop in performance after the first 128GB are used. Yes it can do that under unusual circumstances that don't characterize typical application I/O.

    For example if you wrote a special test program to do massive sequential writes from multiple simultaneous threads spread across many gigabytes of fragmented files. In that case performance would drop dramatically after the first 128GB.

    However back in the real world, that's not how typical apps work. They commonly have good performance on Fusion Drive even when it's fairly full.

    If copying very large files to a Fusion Drive, in that case it might slow down after 128GB storage is used, but it will still preserve performance better than a regular HDD as it fills up.

    It's not that Fusion Drive is better or has no trade-offs but for most users cost is a factor. The OP was concerned about cost, storage space and how he'd have to compensate for the little SSD capacity.

    When I get a new iMac I'll definitely get an SSD version, not because I'm dissatisfied with my FD but I'll be using a large external Thunderbolt array.
  17. cycledance Suspended

    Oct 15, 2010
    full ssd is better.

    - wakes up faster from sleep
    - more responsive
    - generates less heat
    - 100% silent
    - faster transferring/copying

    you have 4 usb3 ports and 2 thunderbolt ports to extend storage on the imac.
  18. foster26 thread starter macrumors member

    Sep 22, 2014
    I am going with SSD for sure are reading more. Thanks everyone!!
  19. Cape Dave macrumors 68000

    Nov 16, 2012

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