SSD Vs Fusion Drive iMac

Discussion in 'iMac' started by tinaberezino, Feb 12, 2015.

  1. tinaberezino macrumors newbie

    Nov 20, 2014
    I opted for the fusion drive when purchasing my iMac.

    My understanding is that a small part of the fusion is SSD storage.

    Just wondering how much quicker SSD only would be as compared to the fusion drive. Would the difference in loading times be negligible?
  2. WilliamG macrumors G3

    Mar 29, 2008
    The answer depends. If the "loading" is done from the SSD portion, it will be fast. From the hard drive, not fast. It's one or the other.

    A pure SSD will be consistently faster. The key is "consistently."
  3. redheeler macrumors 603


    Oct 17, 2014
    The Fusion drives use a slower 128 GB SSD, so even loading data off the SSD is slower compared to a 256 GB SSD.
  4. Roidman macrumors newbie

    Feb 12, 2015
    Really I didn't know that? So would a new base model iMac retina with fusion drive be slower than my early 2013 15mpr base model, to equal it would need to get SSD only iMac retina?
  5. Sciuriware macrumors 6502


    Jan 4, 2014
    If you checksum your favourite files on a regular basis, those files will
    reside in the SSD part of the fusion drive.
    I did some tests and now my files on the iMac with fusion disk read as fast
    as the same files on a MacBook with only SSD.
    Unless someone points out that my MacBook has a slow SSD I think they're
    just the same.
  6. redheeler, Feb 12, 2015
    Last edited: Feb 12, 2015

    redheeler macrumors 603


    Oct 17, 2014
    Is it PCIe or SATA? SATA SSDs are slower than PCIe.


    The 128 GB SSD will be about the same as a rMBP of that vintage because the rMBP predates the switch to PCIe SSDs (it uses SATA). The 256 GB in the SSD-only iMac and modern rMBPs can be up to a third faster with sequential reads/writes since it takes advantage of the faster PCIe speeds.
  7. WilliamG macrumors G3

    Mar 29, 2008
    My 128GB SSD (3TB Fusion) in my 5K iMac reads at ~700MB/s second.
  8. yjchua95 macrumors 604

    Apr 23, 2011
    GVA, KUL, MEL (current), ZQN
    What about the writes? 300-400 MB/s-ish?
  9. gnasher729 macrumors P6


    Nov 25, 2005
    SSD is quicker. Fusion is bigger.

    Figure out how much storage you need. Then check how much it costs as SSD and as Fusion drive. If you need 1TB, then the price tag on the SSD will be frightening.
  10. Sciuriware macrumors 6502


    Jan 4, 2014
    It's NOT only how much storage you need.
    I got 3.25 Tb, but I need about 1.2Tb, that's why the 1Tb is too small for me.
    But the amount of files that I use on regular basis is about 40Gb, so the
    SSD part works well for me.
    Besides, system files are the files most accessed.

    A tip: you can make any hard drive faster by dividing it into 2 partitions:
    partition 1 has all the files frequently accessed,
    partition 2 has the other files.
    Result: less head movement and over a smaller distance.
    But that does not work for a Fusion drive, unless you break the tables open.
    (don't do it Yogy!)
  11. theluggage macrumors 68040

    Jul 29, 2011
    One thing worth remembering about SSD drive "speeds":

    If you're using SSDs because you you need to move huge media files around rapidly, or work with multiple 4k video streaks, then the maximum sustained transfer speed may well be important.

    However, the main point of using a fusion drive - or a small SSD as a system drive - is to reduce the seek time when reading/writing frequently accessed files - particularly when booting, opening applications or swapping memory to disc. Seek time is a major reason why copying a mass of small files from A to B never gets anywhere close to the theoretical transfer speed of the drive. Since SSDs aren't physically moving a mechanical head over a spinning disc, pretty much any SSD will be able to locate and open files vastly faster than a mechanical hard drive.

    The practical upshot of the 128GB SSD's slower transfer rate is going to be your transfer speed benchmark bragging rights. Yeah, faster will always be better but the 128GB drive is probably a sensible choice for a fusion drive that is mainly going to act as a cache.
  12. AppleFan360 macrumors 68020

    Jan 26, 2008
    A lot of good points here. The main thing is either the Fusion or pure SSD system is much faster than a HDD only system. If you have already purchased a Fusion drive and are happy with the storage space, then there is no reason to worry about if the grass is greener on the other side. Many people purchase Fusion drives and are happy with them. Fusion strikes a nice balance between speed, storage a cost.
  13. joema2 macrumors 65816


    Sep 3, 2013
    That is correct, SSD is definitely faster for writes. However in actual use, reads typically outnumber writes by 4-to-1 or more. So Fusion is fast at the most important thing.

    What counts is whether it makes a clear difference in your individual workflow, not whether a benchmark is higher. 600 MB/sec read and 350 MB/sec write are already so high that further improvements often don't translate into a major real-world difference within the app.

    That said, if it's likely a higher speed external drive array will be needed, then an SSD system drive is often a better choice.

    However if the overall budget combined with limited SSD space forces moving frequently-used files to a cheap, slow external HDD, then the overall workflow can be slower than just using Fusion.
  14. Sciuriware macrumors 6502


    Jan 4, 2014
    And when you consider investments, do not forget to buy as much memory as you need.
    I installed 32Gb and as soon as the data is read from any disk, it remains
    a while in memory and any successive data operation on these files beats
    any SSD or such.
  15. JustMartin macrumors 6502a

    Feb 28, 2012
    Although, don't forget that the fusion drive reserves 4Gb of SSD for new writes. So, if you're not doing tons of file transfers in one go, your write speed will still be pretty close to SSD
  16. MacGizmo macrumors 65816


    Apr 27, 2003
    The Fusion Drive is a marketing gimmick. Pure and simple. It exists solely to show a larger storage drive number.

    While the startup time and some app launch times will be faster with Fusion than a regular pure HD, the OS will still use the regular HD part of Fusion for most operations that require disk access–so day-to-day use will barely benefit.

    Pure SSD on the other hand is lightening fast. The speed increase is extremely noticeable at worst, and staggeringly faster at best.

    In other words, if you're looking for speed, pure SSD is the only way to go. It's almost like getting a new computer.

    However, if all you're doing is web/email/office apps type of things, the return on investment in SSD isn't worth it because those apps simply aren't disk-intensive applications to begin with.
  17. WilliamG macrumors G3

    Mar 29, 2008
    Yes, and that's faster than 99.99999% of people will ever need. The key, as mention earlier, is seek times, - because random reads/writes are what SSDs excel at.

    That's why my very first SSD - an OCZ Vertex 120GB (cost me a fortune) had read/write of 220/150MB/s, pathetic in terms of sequential speed by today's standards, but it was - and still - is miles, miles better than a hard drive because of the 0ms seek time. That's the key for general OS use.

    The only people who benefit from <700MB/s read/write are people who copy files to and from external Thunderbolt 2 RAID arrays all day.

    Once you go SSD - and I mean ANY SSD from the last ~6 years, you're in a different league of enjoyment of your computer.


    I wouldn't say it's a gimmick, but it's certainly not in even remotely the same class of speed as an SSD. And with the lack of control over what files go where, it can make using a computer with fusion a bit of a crapshoot. When you open that application, will it open instantly, or will it not? Who knows.

    With Apple's fusion implementation, the first ~128GB always will go to the SSD, so anything beyond that goes to the hard drive, and during drive idle time, Apple decided what files/applications we used the most, and shifts that data from the hard drive to the SSD, and vice versa.

    The problem is, that sort of thing drives me nuts when, e.g. I use iTunes, because there's that delay when starting music because most of it ends up not on the SSD. You can even hear the hard drive grinding away while this is happening. I got driven crazy by fusion in my 5K iMac, so I ended switching to a 1TB Thunderbolt SSD for OS X/Windows 8 boot + music/apps etc.

    That said, there are a LOT of people out there who will be more than happy with fusion. I'm just not one of them. Pure SSD or bust.
  18. DreamGuardian macrumors newbie

    Feb 15, 2015
    It depends on what you are doing.

    An SSD is a must for high resolution video editing. On the other hand an HDD is more than enough for web surfing.

    An SSD will feel faster but in the end, a Fusion Drive is more than enough for everyday usage, unless you want to save a few milliseconds when you open a file.
  19. joema2 macrumors 65816


    Sep 3, 2013
    As a professional video editor, I use HDD-based systems every day on both Windows and Mac and they work fine. SSD is not a must for video editing, in fact it's often a poor fit because the media sizes far outstrip what anyone could afford for SSD.

    If that media is on an external HDD RAID array, then the boot drive may as well be SSD but it's not like Fusion Drive works poorly for that.
  20. DreamGuardian macrumors newbie

    Feb 15, 2015
    I am referring to high resolution (1080p at least or 4K) video. Of course an HDD works, but if you have a large budget, an SSD RAID 0 array will reduce the processing time...
  21. joema2 macrumors 65816


    Sep 3, 2013
    I am editing HD and 4K. My point is that SSD is not "a must". Using a large SSD RAID 0 array typically has little effect on overall processing time vs an HDD RAID array, yet is far more expensive.

    This is because you only need sufficient I/O performance until that element is no longer the bottleneck. Further (expensive) increases in I/O performance won't help because the bottleneck has moved to the CPU, GPU or software internal synchronization.

    Much material is long GOP compressed (H.264, etc) so this reduces the I/O burden at the expense of CPU. Even ProRes 422 HD is only about 18 megabytes/sec, so a lower-end RAID array could handle numerous simultaneous streams.

    In the unusual case of editing raw uncompressed video, the I/O load will be higher but so will the data volume -- so much so it often won't fit on any affordable SSD. E.g, uncompressed RED raw 4k is about 700 megabytes/sec, or 2.5 terabytes per hour.

    Of course with multicam editing each stream adds I/O load, so the disk subsystem should be capable of the aggregate requirement. This can generally be handled with RAID HDD at equal real-world performance and a much lower price than SSD.
  22. DreamGuardian macrumors newbie

    Feb 15, 2015
  23. steve23094 macrumors 68020


    Apr 23, 2013
    You forgot a very important point that OS X automatically transfers your most commonly accessed data to the SSD transparently in the background.
  24. aevan, Feb 17, 2015
    Last edited: Feb 17, 2015

    aevan macrumors 68020


    Feb 5, 2015

    This is just not true. I have a PCIe SSD on my MacBook Pro. It is a fery fast Samsung drive, 700Mbps writes and reads. I also have a 1Tb Fusion Drive on my iMac 5K. I don't see much difference between the two in my regular workflow. I did notice that an app I didn't use for a while took a bit longer to load, but that's it. The system boots really fast, Photoshop opens really fast, apps open fast, etc.

    New Fusion Drives (I think 2013 and up) have PCIe SSDs. If you hate them, you can always manually split them and choose what goes to that fast SSD and what to the HD. I was planning to do that, but found out there really is no need, as Apple does a great job of managing everything.

    Now, SSDs have advantages. Reliability, silence, consistency. Also they don't need to be defragmented (although OS X does this for HDDs in background anyway) etc. Also, some people (video professionals, for example) need really fast speeds for media files. However, claiming that FD is a "marketing gimmick" is just wrong. It just isn't true. I had a HDD-only iMac and it was incredibly slower than the one with the FD.

    I would like to hear what data-intensive tasks you do to consider FD as slow. Did you even try it? And don't give me that 'it's ok for email and surfing' BS. An iPad is good for those - people are creating amazing things with 5, 6, 7 (and more) year old iMacs and a modern computer with a FD is MORE than capable of doing really powerful stuff.

    Besides, if you don't believe me - read this excellent piece by Anand Shimpi

    "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"

    This doesn't sound like a marketing gimmick to me, and - don't take this the wrong way - but I'll take Anand's word over an emotional forum post.

    So - let's put things in perspective:

    SSD is better than a FD but also more expensive.
    256Gb SSD is a good choice if you plan on using external Tb drives.
    FD is a really good option for a lot of people.
    512Gb/1Tb SSDs are amazing and have a price of a whole computer. Not for everyone.
  25. Alesc macrumors 6502


    Nov 11, 2014
    aevan and joema2, thanks a lot for your constructive and clever posts in that topic!

    And off course everybody dream about an affordable 3TB SSD, but it doesn't exist today. And for the price of my 3TB FD, 256GB SSD + fast external storage of 3TB doesn't exist...
    I can't afford pofessionnal fast storage, and I don't wan't a slow external drive for my datas... So in my case, the 3TB FD was the way to go. And I'm very happy with it so far :)

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