iMac internal SSD vs external Thunderbolt SSD

Discussion in 'iMac' started by snapdragonx, Jun 30, 2013.

  1. snapdragonx macrumors regular

    Oct 31, 2012
    Hey guys,

    I'm about to buy myself a 27" iMac. I need the best possible performance for video editing, so I don't want the Fusion Drive as a pure SSD is still faster. But I don't want to pay Apple's crazy prices for a 512GB SSD.

    So, my question. I've heard that it's possible to hook up an external SSD via Thunderbolt and install OS X on it? Would this method be any slower than using the internal SSD? Would seek time be affected?

    I need maximum performance for video editing, so don't want any bottlenecks.

    Any info appreciated!
  2. mmcgann11 macrumors newbie

    Apr 18, 2007
    West Chester, PA
    Yeah, I had the exact same concerns. But looking around, I wasn't entirely thrilled with the options, so I sucked it up and got a 768GB on my BTO (which is now in process).

    Ultimately, I'll be looking for a larger TB SSD — but I've seen enough concerns about some of the enclosures out there right now that I'm willing to wait for better drives to hit the market. In the meantime, I'll be looking at reworking my file management to keep my FCPX/Motion files on an external USB 3.0/TB drive, possibly set up in a RAID — to avoid those bottlenecks.
  3. Weaselboy, Jun 30, 2013
    Last edited: Jun 30, 2013

    Weaselboy Moderator


    Staff Member

    Jan 23, 2005
    Here is a thread with a bunch of folks doing exactly what you described along with some speed tests.
  4. Chippy99 macrumors 6502a

    Apr 28, 2012
    And to save you wading through the thead, the seek times are not affected. But that is not very important for video editing. What you need to be concerned about is the transfer rates, and these are affected, depending on the controller in whichever Thunderbolt adapter you go for. Some of them are SATA II only and becuase of that (and probably other reasons too) are not as fast as an internal SSD connected to the SATA ports directly.

    That said, they can still be pretty fast and with the right controller, just as fast as internal. You need to shop around and do your homework.
  5. flynz4 macrumors 68040

    Aug 9, 2009
    Portland, OR
    I suspect (based on MBA and Mac Pro announcements) that when the iMac is updated, the new SSDs will be PCIe attached... which also improves latency and transfer rate.

    Like you, I also went with the 768GB SSD and I paired it with an external Thunderbolt HDD array (8TB Pegasus R4). I can edit videos on the 768GB SSD, and then migrate the completed projects to to the Pegasus array.

  6. KaraH macrumors 6502

    Nov 12, 2012
    I am on the fence about getting one now. The SSD has a shorter lifespan than how long I keep macs. While the ideal use case for an SSD is OS and applications I am not wild about putting those on an external device (one more thing to get unplugged at the wrong time). If the iMac was easier to open an internal SSD just MIGHT be an option.

    I am thinking about waiting a generation or two for the internal ... both for prices to go down and for lifetimes to go up. Possibly an external for applications but not the OS.
  7. flynz4 macrumors 68040

    Aug 9, 2009
    Portland, OR
    Like you, I dislike using an external drive for a boot/system device. Inadvertent removal is just too easy. Even in datacenters with trained staff and strict procedures... the wrong cable getting unplugged is one of the leading causes of failure.

    However, I disagree about the lifespan of SSDs. They are certainly longer now than HDDs, and will likely last decades. Longevity is a reason to buy (not avoid) SSDs.

  8. snapdragonx thread starter macrumors regular

    Oct 31, 2012
    Thanks for the advice all.

    I'm tempted to just go for the Fusion Drive to be honest. A BTO 512GB SSD is an extra $960 here in NZ which is just crazy.

    But I'm just worried that with the Fusion Drive, I'll be going backwards in performance compared to my old rMPB.
  9. KaraH macrumors 6502

    Nov 12, 2012
    Yes, I am all too familiar with how things can go wrong in a datacenter accidentally. These are people who certainly know tech issues but accidents happen. Which is why I prefer something like a tower form factor (which apple no longer makes) as that keeps as many connections as possible away from where they can get bumped.

    It seems to be a mixed bag. Some people quote under 2 years, some decades. It depends on quality and usage. Apple uses two different ones last I knew and one is better than the other. Plus there is fusion and how that uses the drive (constantly moving blocks between the SSD and the HDD can not be good for your write count). If it were not for fusion I would reformat the drive to not use 27% of the space.

    An internal SSD would be nice but I am leaning to an external one for frequently used applications (possibly also the OS but keeping an internal copy too). It is a bit early in the technological cycle to have it be in what is literally a glued up box. Plus I can get a good quality one for less expense.
  10. Insar, Jul 8, 2013
    Last edited: Jul 8, 2013

    Insar macrumors newbie

    Apr 28, 2013
    I bought the macmail lacie little big disk sata 2 ref for $ 160 I am very pleased with my purchase. After hdd replacement on the ssd Vertex 4 128gb in RAID0 speed is very good

    I also replaced the internal hdd to ssd samsung 830 256gb and SSD Apple 256gb in RAID 0 speed is excellent. The difference in the speed of work of the iMac, I have not noticed.

    Attached Files:

  11. whooleytoo macrumors 604


    Aug 2, 2002
    Cork, Ireland.
    Ditto on the worries about external drive. Bought a 2013 iMac recently and though I'm happy with it the hard drive is sloooow. Definitely considering installing the OS & apps on an external TB SSD.

    I'm not sure if there's a disadvantage in having the pagefile on an SSD (in terms of reducing the lifetime) - but this test is very encouraging - they stress tested several SSDs continuously for 10 months before any started failing - well beyond the manufacturers' recommended lifetime write limits.

    Now it's just a matter of finding a good, fast, reliable, cheap one! :)
  12. yjchua95 macrumors 604

    Apr 23, 2011
    GVA, KUL, MEL (current), ZQN
    Only an internal SSD will give maximum performance.

    A single external Thunderbolt SSD won't even give full SATA3 speeds, due to overhead.

    External Samsung 840 Evo 500GB - 430MB/s read/write (mounted in a Buffalo HD-PATU3 TB enclosure)

    Internal SM0512F 512GB PCIe SSD - 750 MB/s read and 720MB/s write.

    In normal usage you won't notice any difference. In I/O intensive tasks like heavy video editing.

    I'd suggest you to just save up for a bit longer and go for a 512GB option.
  13. SaSaSushi macrumors 68040


    Aug 8, 2007
    Takamatsu, Japan
    The post you were replying to is a year old, so I have to assume he's probably made his decision by now. :p

    Even though I got my Late 2013 iMac with a 1TB Fusion Drive this is exactly what I've done, booting OS X off a 500GB Samsung 840 EVO SSD (split half and half with BootCamp) in a Delock 42490 Thunderbolt enclosure.

    I couldn't be happier with it. :)

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