Question regarding booting OSX from an SSD via USB3/TB

Discussion in 'iMac' started by dandingo, Oct 22, 2014.

  1. dandingo macrumors newbie

    Joined:
    Oct 17, 2014
    #1
    Hi there,

    I'm a photographer and planned on returning to a Mac after a few years of hiatus. I have been patiently waiting for the new Mac Mini for over a year and now, with the news of no more quad cores, I'm seriously considering a 27" iMac even though they're just out of my budget.

    I could get a 2012 MM but after installing an SSD on my PC, I won't go back to a spinner. I also just can't see spending over $1200 for a 2012 after getting one with enough RAM, SSD and keyboard and mouse when I can spend a few hundred more and get an i5 27".

    The problem is, I'm looking at the refurbished ones and haven't seen one with an SSD in my price range. My question is would booting from an SSD via USB3 or Thunderbolt give me close to the performance as installing one internally? If so, I may consider an iMac. Thanks in advance!
     
  2. Cape Dave macrumors 68000

    Joined:
    Nov 16, 2012
    Location:
    Northeast
    #2
    You are right. SSD is the way to go :)

    I read somewhere that one cannot boot from USB3, just Tbolt. Was some on this forum, but I cannot remember where. It seems to be that I have booted from a USB3 external, but it was long ago and I cannot remember for sure.

    This is hyper fast but big $$$ https://www.lacie.com/US/products/product.htm?id=10621
     
  3. Weaselboy Moderator

    Weaselboy

    Staff Member

    Joined:
    Jan 23, 2005
    Location:
    California
    #3
    Yes it works quite well with either. You should go with Thunderbolt though because USB does not support TRIM on SSDs and TB does.

    Here is a thread discussing doing exactly what you want. Might give you some insight. :)
     
  4. theSeb macrumors 604

    theSeb

    Joined:
    Aug 10, 2010
    Location:
    Poole, England
    #4
    You can boot from USB 3 or Thunderbolt. If you're a masochist, you can even boot from USB 2.
     
  5. yjchua95 macrumors 604

    Joined:
    Apr 23, 2011
    Location:
    GVA, KUL, MEL (current), ZQN
    #5
    It'll never reach the same as a native PCIe SSD in the iMac, because the only SSDs available in the market are all SATA3.

    An internal PCIe SSD in an iMac reaches around 750 MB/s in both reads/writes, while even the fastest SATA3 SSD in a Thunderbolt enclosure would top out at around 520-550 MB/s.

    That said, I doubt you'd notice any difference in daily usage, unless you do I/O intensive operations.

    I'd stick to a TB enclosure for an external SSD though, just for the sake of TRIM.
     
  6. Melodeath macrumors 6502a

    Joined:
    Dec 9, 2009
    #6
    Is this a limitation of external SSDs, or will things change in the near future? So PCIe SSD are only available to Apple? I don't really understand.
     
  7. Chippy99, Oct 23, 2014
    Last edited: Oct 23, 2014

    Chippy99 macrumors 6502a

    Joined:
    Apr 28, 2012
    #7
  8. g4cube macrumors 6502a

    Joined:
    Apr 22, 2003
    #8
    Actually, the picture you are showing of an M.2 SSD is a SATA SSD in an M.2 form-factor.

    An M.2 SSD with a PCIe SSD looks like this:
    [​IMG]

    And the Apple PCIe SSDs look like this:
    [​IMG]

    Note the OP's image and the two I posted all have the keying in a different location.

    The OP's image shows keying for a SATA M.2 stick.
    The XP941 I show in the first picture shows the standard PCIe keying for an M.2 stick
    The Apple pic shows the nonstandard keying for Apple's proprietary PCIe SSDs.

    You can use the XP941 of the first image in a PCIe expansion chassis provided you also have the correct PCIe card to mount the SSD. There are other threads here in the forums that describe this in more detail.
     
  9. Cape Dave macrumors 68000

    Joined:
    Nov 16, 2012
    Location:
    Northeast
    #9
  10. Chippy99, Oct 24, 2014
    Last edited: Oct 24, 2014

    Chippy99 macrumors 6502a

    Joined:
    Apr 28, 2012
    #10
    Sorry but you are mistaken and it is a native PCI-Express SSD. But it is confusing and I can see that M.2 cards with 2 notches are sometimes believed to be SATA M.2 cards, but this is not the case.

    Here's the product in more detail:

    [​IMG]

    "Plextor's M6e M.2 2280 PCIe Gen2 x2 is an ultra-fast SSD, which uses the latest generation of components and a native PCIe interface for extremely high performance. ... By bypassing the 6Gbps limit of the SATA Rev 3.0 interface, Plextor's M6e M.2 is able to reach maximum sequential read speeds of 770MB/sec and sequential write speeds of 625MB/sec. Its 4K random speeds top out at 105K and random write speeds go up to 100K IOPS. Performance that translates into fast level load, quick boot times, smooth video editing and more."

    http://www.plextoramericas.com/index.php/pcie-ssd/m2/m6e-m2-2280

    In any event I accept it is M.2 and you do need an adapter to plug that into a normal PCI Express slot. So perhaps I should have shown this product, which is exactly the same SSD but comes with the required adapter:

    http://www.plextoramericas.com/index.php/pcie-ssd/hhhl/pcie-m6e

    I note that this product needs no special drivers and should work fine with OS X, including being bootable and supporting TRIM. I am not recommending it in particular however, merely demonstrating to yjchua95 and others, that they do exist and it is possible to have a Mac with an externally mounted, full performance, PCI-Express SSD.
     
  11. g4cube, Oct 24, 2014
    Last edited: Oct 24, 2014

    g4cube macrumors 6502a

    Joined:
    Apr 22, 2003
    #11
    Thanks for setting the record straight.

    Only difference is that the Plextor is a 2-lane PCIe SSD while the Samsung XP941 is a 4-lane PCIe SSD, which in theory provides more bandwidth.

    http://rog.asus.com/313352014/labels/guides/buying-an-m-2-ssd-how-to-tell-which-is-which/ this article explains keying of the M.2 connector.

    Attached is a pic showing AJA R/W performance of a 512GB XP941 connected via Thunderbolt2 to a nMP. Would be good to see how the Plextor does in comparison. By the way, newegg.com is now selling the XP941 for a price just north of $500. I tested the XP941 in a LaCie Little Big Disk Thunderbolt2 by reformatting as two separate volumes instead of the default RAID-0 array.
     

    Attached Files:

Share This Page