Another Fusion vs. SSD/external question

Discussion in 'iMac' started by jazzer15, Dec 15, 2015.

  1. jazzer15, Dec 15, 2015
    Last edited: Dec 15, 2015

    jazzer15 macrumors 6502

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    #1
    Trying to get my head around some of the issues in the Fusion vs. SSD debate.
    Would accessing data that is NOT frequently used be faster on a FD because that data is stored locally vs accessing that same data on, for example, a portable bus powered USB 3 external drive?
     
  2. twilexia macrumors 6502

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    #2
    If it's a portable bus-powered HDD, yes, with a few exceptions - Seagate Backup Plus Fast has speeds often faster than the internal 7200 rpm HDD.

    If it's a portable bus-powered SSD, no.
     
  3. jazzer15 thread starter macrumors 6502

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    #3
    What if comparing the internal 7200 rpm HDD to a similar external drive using USB 3 or Thunderbolt? I'm just trying to get a sense of what type of external drive (other than an SSD) is needed to surpass the speed of the internal HDD.

    Sounds like if I want something small and unobtrusive the Seagate Backup Plus Fast is a good option, as someone had pointed out to me before.
     
  4. twilexia macrumors 6502

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    #4
    7200 rpm external HDDs usually average 100-120 MB/s. Anything faster would probably be a 10k rpm HDD or a 15k rpm HDD if you can find it. Otherwise, you'd have to RAID two or more HDDs together and that usually requires an additional AC power source (but since you asked for bus-powered, Seagate Backup Plus Fast is really the only one I can think of).
     
  5. jazzer15 thread starter macrumors 6502

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    #5
    Thanks. I'm not necessarily set on bus powered -- although it is nice to not have a power adapter -- I was just using that as an example. I was simply trying to figure out how the internal and external options compared. I don't have a need for the fastest external drive out there, but I would like my external drive(s) to be at least not noticeably slower than using an internal HDD if possible - although obviously the vast majority of work will occur on the SSD.
     
  6. MadDane macrumors 6502a

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    #6
    When the drive is up and running there should be no real difference between internal and external, if using USB3 or Thunderbolt. Since USB3 is faster than a HDD the connection will not be the bottleneck. It is the drive itself that will be, whether it is internal or external.

    To put some numbers on it. If you take a standard 7200 rpm internal HDD you will get typically between 50 - 120 MB/s (link) or even 123/141 MB/s read/write (link).
    If you take a standard USB powered external HDD, you can expect something like 88/119 MB/s read/write (link).
    If you then look at the Seagate Backup Plus Fast that twilexia referred to, it has speeds of 183/237 MB/s read/write (link).

    In other words, yes an external USB3 powered drive will perform identically as an internal one, when it is up and running. Getting it started might create a slight lag, but having experience with a Fusion Drive you will experience the same thing when the drive needs to get started in one of those.
     
  7. jazzer15 thread starter macrumors 6502

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    #7
    Thank you for the explanation and links. So essentially since USB3 and/or Thunderbolt would be faster than the HDD connection, if I want to keep cost more reasonable and the fastest speed is not required, USB3 would be the better option (because it is less expensive) and then I would just have to choose a drive that is faster than the HDD drive used as part of the FD, right? So, is there data as to what HDD(s) Apple uses and a rating of its/their speed?
     
  8. MadDane macrumors 6502a

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    #8
    Yes, correct. USB3 is more than fast enough for a HDD, unless you use many of them in RAID 0. It is only if you want an external SSD that Thunderbolt really makes sense, since it supports TRIM.

    I am not aware of any data of which drives Apple uses. I have seen both Seagate, WD and Toshiba in the past. But assuming you are looking at a 27" iMac, here is an example where a Seagate ST1000DM003 (1TB) HDD was used (link). If you look at the data sheet for that model (link) you can see that it is rated at up to 210 MB/s and an average data rate of 156 MB/s for both read and write. Again, this might not be the actual numbers, but that is what they are rated at. If you then look at the Seagate Backup Plus Fast it is rated at up to 220 MB/s (link to data sheet) and it has, as I described in my previous post, pretty good real world performance. If you use a combination of pure internal SSD with a Seagate Backup Plus Fast, you will most likely gain speed compared to a Fusion Drive. However, the perceived difference might be negligible.

    TL;DR: Yes you can achieve similar speed as with a Fusion Drive, by using an external USB3 HDD for storage.
     
  9. twilexia macrumors 6502

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    #9
    My understanding was TRIM is also available for USB 3 for some of the newer SSDs (e.g. Samsung Evo 850)?
     
  10. MadDane macrumors 6502a

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    #10
    I have not heard of any SSD's that supports TRIM over USB, though you might be right. A quick Google search did suggest something about that it might be possible with UASP. Do you have some data indicating that it works? Trust me, I would love if it did. Then I would definitely get myself a 500 GB SSD to use externally over USB (Thunderbolt is still too expensive for my liking).
     
  11. maflynn Moderator

    maflynn

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    #11
    Does the OS support Trim over USB, I didn't think OS X did, but then I really don't follow that sort of news so I may be completely wrong.
     
  12. Weaselboy Moderator

    Weaselboy

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    #12
    Nope... TRIM is a SATA command and USB is not capable of transmitting that SATA command. What you may have read is what MadDane touched on. UASP USB enclosures essentially mimic SCSI over USB, so some have theorized that that UASP controller could also convert the SATA command to SCSI and pass it along over USB. But everything I have read shows that is just a theory and no tests have shown it works.
     
  13. T Coma macrumors regular

    T Coma

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    #13
    Not content with the guesses, I checked some speeds on a few similar drives and posted here:
    http://forums.macrumors.com/threads/external-thunderbolt-enclosure.1905587/page-3#post-22331650
     
  14. jazzer15 thread starter macrumors 6502

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    #14
    Thanks.

    I'm not sure if I fully understand your test (BTW, it sounds like you know what you are doing to me :confused:), but if I do, you are showing that an external SSD is a good bit faster than the internal HDD but an external 5400 rpm USB3 drive runs slower.

    I am trying to find a sweet spot for the external drive where I still would get a good bit of storage space at a good price, but at least match the speed of an internal HDD in a fusion drive machine. I suspect moving from a 5400 rpm portable to a 7200 rpm external even on USB 3 would probably do the trick while I would need the Seagate Backup Plus Fast, which uses a Raid 0 configuration, if I want a faster bus powered drive.
     
  15. T Coma macrumors regular

    T Coma

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    #15
    :confused:
    That would seem to make sense. I have a collection of usb3 external drives for storage, video, photo, time machine, and others. I'm quite happy with their speeds for my purposes, and i do a lot of file transfers. I'm not sure if any of them are 7200 rpm speed, but I can check and post the test results if so.
     
  16. Samuelsan2001 macrumors 603

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    Oct 24, 2013
    #16
    After all this you need a basic answer, running an external USB 3 drive will be no slower than an internal HDD and no faster either.

    If you go SSD (256 or 512) you'll have a load of internal superfast space for apps and frequently used files and what you are currently working on and an external will be absolutely fine for all your media files etc. Anything you are working on in FCPX or Adobe etc will probably benefit from being on the SSD while working on it but will be fine on the external for playback etc.

    To be honest though if you aren't doing huge 4K projects or working with big RAW files the fusion drive 2TB with it's 128Gb SSD will probably be a great solution.
     
  17. maflynn Moderator

    maflynn

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    #17
    For me, I wanted a SSD, but if I went with the 256GB (or even the 512GB), I'd need to use an external drive. I've been bound to one now for a couple of years, juggling what should be on the SSD and one goes to the external drive. I was tired of such actions, so I bit the bullet and opted for the 2TB Fusion drive. So far, I'm very happy with - no complaints.
     
  18. jazzer15 thread starter macrumors 6502

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    Oct 8, 2010
    #18
    Thanks for your thoughts on this. I decided to go with the i7 with 512GB SSD, for better or worse. It just arrived at the end of last week (kudos to Apple customer service for speeding processing after a mistake I accidentally made while ordering) and I spent some of the weekend starting to set it up.

    At the moment I have a 2TB USB powered portable drive connected that I transferred my music, photos and Various other data to. It seems to be working fine and I like the small size, but I wonder if there might be any benefit to getting a 7200 rpm drive for storage. I am also going to need to buy a larger drive (perhaps another portable) for backup.

    If I really trimmed back my files, I might be able to fit most, if not all on the 512GB SSD, but it would be mostly full. And, as my (hobby) photo editing involves processing 24 megapixel RAW files, some of which get further processed and saved as larger Tiff or PSD files, even if I could possibly squeeze everything on the drive today, I would definitely need more space rather quickly.

    Having had a 2TB HDD in my last iMac (and plenty of space and open drive bays in my PCs before that), managing data with external drives is new territory for me. It doesn't seem like it will be a problem, especially because the iMac is not going to be moved around like a laptop would, but I admit that I wonder a little if it wouldn't just be easier and more efficient, without any noticeable performance difference, to have a large fusion drive. On the other hand, the SSD is certainly fast ... and silent.

    No complaints so far, but it is in my nature, I guess, to continue to consider the alternatives. The only questions are whether a Fusion Drive might have made more sense and whether a video card upgrade from the 395 to the 395x might have been a good choice for the long run (it is certainly not needed now).
     

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