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macrumors newbie
Original poster
Feb 25, 2008
Just got an brand new 27" iMac, 512Gb flash drive and wondering if I should go with a USB or TB for a HD and if there are any suggestions for brand.


macrumors 6502a
May 10, 2012
San Francisco
Since you'll be relying on this for storage, because the internal storage is relatively small, thunderbolt. Without a question. You've already shown you can pay a premium price. Thunderbolt for you, without a doubt.


macrumors 6502
Jan 11, 2015
it makes not one bit of difference. The speed of the USB3 vs Thunderbolt interface is getting into splitting hairs. Unless you are going with a multi hard drive RAID0 case then you will be limited by the drive speed. Even a single SSD can't exceed to throughput enough to clearly justify one over the other.

Just buy what is available at a price you are willing to pay.
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macrumors 601
Jul 9, 2012
If the external drive is a single spinning HD, you will not see the speed benefit of TB. The drive itself is too slow. You are just as well off to get a cheaper USB 3 enclosure.

If the external drive is an SSD, then you have two choices. The first is to put the SSD in a USB3 enclosure that does the UASP protocol. The second choice is a TB enclosure. The performance would be about the same with the USB3-UASP enclosure being cheaper.

BTW. don't forget a separate external drive for backups!

Clix Pix

macrumors demi-goddess
Check out Samsung's T1 or the new T3 SSD external drives. The T3 comes in a 2 TB capacity plus smaller sizes, and the T1 is available in a 1 TB size as well as the smaller capacities. This is a very fast, physically small bus-driven USB 3.0 connection external drive that works well as a supplemental drive when one has a computer with limited SSD capacity. I bought a retina MacBook Pro (512 GB SSD) in December and shortly after setting it up also purchased a 1 TB Samsung T1 to use as a supplemental drive. I also have various other external drives that are used for backup purposes. The T1 or T3 are not inexpensive, but I think that the SSD speed and the incredibly small size, great for travel, makes it worthwhile.

If you're after more capacity than this, since you're using a desktop machine and portability might not be all that important to you, the Seagate Backup Plus drive comes in various capacities, I think up to 4 TB, perhaps more, and it again plugs into a USB 3.0 port.
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macrumors 65816
Nov 14, 2009
TB vs USB3 is abut the same thruput (~400 MB/sec) with a single SSD, but where TB really shines is in multibay enclosures with RAID.
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Staff member
Jan 23, 2005
It is, all you have to is compare the two side by side.

I'm surprised so many on this site are saying USB 3 is right up there with TB. TB is easily faster.
For a single SSD drive, not really. They are very close to the same. See this test.

OP> I would just get a UASP compatible USB3 enclosure like this one then pop in an SSD in whatever size you want. The Samsung EVO 850 and Crucial MX200 are very popular and reasonably priced now.

The only real benefit of TB for this usage is TB can run TRIM on an eternal SSD where USB cannot.
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macrumors G4
Jan 8, 2012
Its important we know what the space going to be used for? For all we know a NAS could be your best choice.

Please please PLEASE don't listen to people that would blindly recommend thunderbolt without a use case. Thats like a doctor prescribing you medications from the diagnostic being "sick"


macrumors regular
Nov 12, 2012
if ur external drive is going to be a ssd i would go with thunderbolt.thunderbolt is a lot faster with ssd than usb


macrumors Penryn
Feb 20, 2009
If one is connecting a single drive (particularly a platter-based drive) to the Mac, USB3 is both economical and the "speed-equal" of thunderbolt.

One can pay more for thunderbolt and smile with a bit of snob appeal, but that's about the only benefit you'll get out of it.

Even with an SSD, they're all-but equal.
Granted, USB3 can't support TRIM, but for all practical purposes, TRIM is of little importance.

I've been booting and running my late-2012 Mac Mini for over 3 years now from a USB3 "external booter", with -NO- noticeable drop in performance...
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