Using external USB2 SSD as boot drive for iMac

Discussion in 'iMac' started by dhmitchel, Aug 1, 2010.

  1. dhmitchel macrumors newbie

    Joined:
    Aug 1, 2010
    #1
    Hi,

    I am considering purchasing a new iMac to replace my first generation Macbook Air. I was then planning to install Snow Leopard on an external USB2 SSD and to use that to boot my iMac and then as my primary hard drive.

    My aim in doing this is so that I can effectively still bring my computer with me (in the form of the external SSD) and then boot it up using any Mac (such as my Macbook Air) with high enough technical specifications to run Snow Leopard.

    Before investing in the hardware, I was hoping someone would be able to tell me:

    1. Whether or not this will work;
    2. Whether or not there are any significant disadvantages in running my system this way; and
    3. Whether anyone has tried this.

    Thanks for your help,
    DHM
     
  2. DoFoT9 macrumors P6

    DoFoT9

    Joined:
    Jun 11, 2007
    Location:
    Singapore
    #2
    good choice getting the iMac ;)

    1. yes, this will work.
    2. yes, there are significant disadvantages - these all relate to performance.

    you can expect anywhere from 20MB/s up to 40MB/s stable read/write rates - this depends on the quality of the enclosure that you purchase.

    given that SSDs can perform at 200MB/s and greater, this is a SIGNIFICANT performance hit - you may as well purchase a normal HDD (~100MB/s read/write rates these days).
     
  3. dhmitchel thread starter macrumors newbie

    Joined:
    Aug 1, 2010
    #3
    Thanks DoFoT9.

    The reason for the SSD is that I will be cycling with the external drive in my backpack a lot and don't want an HDD failure.

    Will the performance drop be noticeable when I will generally use the computer for Office applications (largely Entourage and Word) and we browsing (Safari)?

    Thanks again,
    DHM
     
  4. DoFoT9 macrumors P6

    DoFoT9

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    #4
    a mechanical hard drive that is not powered at all can sustain being dropped and will still work perfectly, so long as the head is parked. if its spinning/moving then that is another issue :(

    as for performance of Word/entourage/Safari - it will be fine for that. the benefits of SSD is no latency, so it will still be very snappy.
     
  5. dhmitchel thread starter macrumors newbie

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    Aug 1, 2010
  6. DoFoT9 macrumors P6

    DoFoT9

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    #6
    all good. goodluck!
     
  7. rnb2 macrumors regular

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    Jan 23, 2006
    Location:
    West Haven, CT, USA
    #7
    This is a workable plan if you go FW800, but not if you go USB. I'm booting my 2009 i7 iMac from an SSD in a FW800 enclosure, and it works great.

    True, you do lose the high sustained transfer rate you'd get via SATA, but the lack of latency and extremely fast random seek times make the FW800 SSD a better performer for the OS and Applications than the internal SATA HD. The more data (movies, etc) you put on the SSD, the more you will be hampered by the FW800 connection, but for OS/Applications use, it's a nice setup.
     
  8. bobm macrumors member

    Joined:
    Aug 10, 2006
    #8
    Boot time?

    rnb2, any chance you can post your boot up time with the Firewire 800/SSD?

    Also xbench would be interesting.

    thanks,
    bob

    <edited to change the name since I referenced the original author instead of rmb2>
     
  9. Fishrrman macrumors G4

    Fishrrman

    Joined:
    Feb 20, 2009
    #9
    "I am considering purchasing a new iMac to replace my first generation Macbook Air. I was then planning to install Snow Leopard on an external USB2 SSD and to use that to boot my iMac and then as my primary hard drive.
    My aim in doing this is so that I can effectively still bring my computer with me (in the form of the external SSD) and then boot it up using any Mac (such as my Macbook Air) with high enough technical specifications to run Snow Leopard."

    This will work, although there may be speed "limitations" that become noticeable by virtue of the fact that even a firewire 800 external enclosure will "throttle back" the speed of the SSD drive inside.

    I would STRONGLY suggest that you buy an external enclosure _separately_ to suit your needs, and then add the drive of your choice.

    I would also STRONGLY suggest that the enclosure you purchase have the following connection schemes:
    - Firewire 800
    - Firewire 400 (if you have fw800, this isn't really necessary)
    - USB 2

    You DEFINITELY want firewire if your desire is to have an external drive that is going to be your "main" drive.

    This will give you the ability to connect to any Mac, and if the Mac has firewire 800, it will be the fastest way to go.

    Also be aware that if you are going to rely on "booting externally" via USB, you had better have an external power source for your portable drive, as well. I have seen numerous instances where trying to boot a Mac via USB from a portable drive FAILS because the USB port can't supply enough power to get the external drive "up and running". This is because (for some reason that Apple has never really given a suitable explanation for) not all Mac USB ports "are created equal", and typically, the power output from a Mac USB port is _lower than_ that from a PC's USB port. There are workarounds, such as using a "dual-headed" USB connecting cable, but even this is no guarantee that you'll get a good boot on a Mac from a USB portable drive. The ONLY way to be sure is to have an external power supply or power brick that you can use with the portable USB drive to ensure that it has enough power to get going at boot time.

    This isn't the case with firewire, however. The Mac's firewire specs are such that the firewire ports on a Mac _do_ supply enough bus power to power up a portable firewire drive to boot from it (I'm talking 2.5" "laptop-type" drives here, not 3.5" drives).

    I've never had a problem booting a Mac from a 2.5" drive in a firewire enclosure. I've had numerous problems trying to boot a 2.5" drive from a USB enclosure, however. Be forewarned.

    So, to be sure that you can boot a Mac -- either USB2 or firewire -- from your external drive, your "kit" should include the following:
    - Drive itself in an enclosure with BOTH USB2 and Firewire
    - An external power supply for the drive, in case you have to boot from USB2 and the Mac has trouble supplying enough power
    - Firewire 800-800 cable (for Macs with fw800 port)
    - Firewire 800-400 cable (for Macs with fw400 port -- will still work with fw800 so long as you have a 9-pin/6-pin cable)
     
  10. shanmugam macrumors 68020

    shanmugam

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    Sep 24, 2008
    Location:
    Blazer town!
    #10
    i am interested in this solution for my iMac 21.5" (2009) model.

    How do i access the internal iMac hard drive once i boot from Firewire SSD drive?

    my plan

    1) clone the iMac hard drive to SSD drive
    2) connect SSD via the firewire 800 and boot from there
    3) and use the 1TB internal iMac hard drive as media drive.

    any help is appreciated! I am very near to getting SSD this thanksgiving :D
     
  11. shanmugam macrumors 68020

    shanmugam

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    Sep 24, 2008
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    Blazer town!
    #11
    Any Help?

    thinking of getting these two

    1) http://eshop.macsales.com/item/Other World Computing/MSTG800U2K/

    2) http://www.newegg.com/Product/Product.aspx?Item=N82E16820227543

    thanks in advance for any advice (i understand with booting via firewire the speed is limited to 100MB/s but that read speed is plenty for my type of use)

    i am scared to open the iMac and remove the 1TB HDD and replace it with a SSD so going this firewire route.

    My major doubt, once i boot from firewire SSD can i use (access) 1TB HDD (once formatted) for storage (like media and others)??? :confused:
     
  12. Hellhammer Moderator

    Hellhammer

    Staff Member

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    Dec 10, 2008
    Location:
    Finland
    #12
    I would get Vertex 2 instead of Agility 2. Vertex two has 5 times better IOPS (random performance) and costs only 5$ more.

    As for the 1TB HD, yes you can access it normally when booting from the FW800 drive.
     
  13. spinnerlys, Nov 3, 2010
    Last edited: Nov 3, 2010

    spinnerlys Guest

    spinnerlys

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    #13
    Your internal HDD will still be visible and fully accessible while booted from the external HDD.
     
  14. shanmugam, Nov 3, 2010
    Last edited: Nov 3, 2010

    shanmugam macrumors 68020

    shanmugam

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    Sep 24, 2008
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    #14
    thanks Hellhammer and spinnerlys. Appreciate the help :)

    Sure i will look out for vertex 2 instead of Agility 2.

    I am looking at a 2.5" drive and enclosure.

    just in the case if this setup did not work out with iMac then at least i can use the SSD in my macbook so going with a 2.5" drive and enclosure (also 2.5" does not need power supply compared to 3.5" enclosure)
     
  15. shanmugam macrumors 68020

    shanmugam

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    Blazer town!
    #15
    Which SSD to chose from?

    I am kinda of confused which SSD to chose from

    1) Intel SSD (intel Controller) but no TRIM Support Read/Write speed is ok

    2) OCZ Vertex 2 /OWC Extreme Pro (Sand force controller) Read/Write Speed is great - but trim? garbage collection?

    3) Kingston V+ (V Plus) Series - Toshiba controller - Garbage Collection - Write speed is not that great.

    Which is best?
     
  16. rtrt macrumors 6502a

    Joined:
    Jan 19, 2008
    #16
    have seen annand recommend sandforce for macos boot. i was happy to take that as a recomendation. i've just picked up a vertex 2 on the basis that it was 10% cheaper than the corsair.
     
  17. George Knighton macrumors 6502a

    George Knighton

    Joined:
    Oct 13, 2010
    #17
    For whatever it is worth, I have a Vertex 2 in my MacBook, and I am delighted with it.

    I picked it based on what appeared to be multiple, informed recommendations and what was at the time a huge price difference because of a Newegg sale.
     
  18. shanmugam macrumors 68020

    shanmugam

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    Sep 24, 2008
    Location:
    Blazer town!
    #18
    thanks for the replies. will look out for vertex 2 (Sandforce) SSDs.
     

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